feat(render-parity): add deterministic frame comparison tool

- Introduced `render-parity` crate for comparing rendered frames against reference images.
- Added command-line options for specifying manifest and output directory.
- Implemented image comparison metrics: mean absolute difference, maximum absolute difference, and changed pixel ratio.
- Created a configuration file `cases.toml` for defining test cases with global defaults and specific parameters.
- Added functionality to capture frames from `render-demo` and save diff images on discrepancies.
- Updated documentation to include usage instructions and CI model for automated testing.

.gitea/workflows/test.yml

@@ -25,3 +25,31 @@ jobs:
       - uses: dtolnay/rust-toolchain@stable
       - name: Cargo test
         run: cargo test --workspace --all-features -- --nocapture
+
+  render-parity:
+    name: Render parity
+    runs-on: ubuntu-latest
+    needs: test
+    steps:
+      - uses: actions/checkout@v6
+      - uses: dtolnay/rust-toolchain@stable
+      - name: Install headless GL runtime
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y xvfb libgl1-mesa-dri libgles2-mesa-dev mesa-utils
+      - name: Build render-demo binary
+        run: cargo build -p render-demo --features demo
+      - name: Run frame parity suite
+        run: |
+          xvfb-run -s "-screen 0 1280x720x24" cargo run -p render-parity -- \
+            --manifest parity/cases.toml \
+            --output-dir target/render-parity/current \
+            --demo-bin target/debug/parkan-render-demo \
+            --keep-going
+      - name: Upload parity artifacts
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: render-parity-artifacts
+          path: target/render-parity/current
+          if-no-files-found: ignore

crates/render-demo/Cargo.toml

@@ -5,7 +5,7 @@ edition = "2021"
 
 [features]
 default = []
-demo = ["dep:sdl2", "dep:glow"]
+demo = ["dep:sdl2", "dep:glow", "dep:image"]
 
 [dependencies]
 msh-core = { path = "../msh-core" }
@@ -13,6 +13,7 @@ nres = { path = "../nres" }
 render-core = { path = "../render-core" }
 sdl2 = { version = "0.37", optional = true, default-features = false, features = ["bundled", "static-link"] }
 glow = { version = "0.16", optional = true }
+image = { version = "0.25", optional = true, default-features = false, features = ["png"] }
 
 [[bin]]
 name = "parkan-render-demo"

crates/render-demo/README.md

@@ -23,6 +23,25 @@ cargo run -p render-demo --features demo -- \
 - `--model` (опционально): имя модели; если не задано, берётся первая `.msh`.
 - `--lod` (опционально, default `0`).
 - `--group` (опционально, default `0`).
+- `--width`, `--height` (опционально, default `1280x720`).
+- `--angle` (опционально): фиксированный угол поворота вокруг Y (в радианах).
+- `--spin-rate` (опционально, default `0.35`): скорость вращения в интерактивном режиме.
+
+## Детерминированный снимок кадра
+
+Для parity-проверок используется headless-сценарий с фиксированными параметрами:
+
+```bash
+cargo run -p render-demo --features demo -- \
+  --archive "testdata/Parkan - Iron Strategy/animals.rlb" \
+  --model "A_L_01.msh" \
+  --lod 0 \
+  --group 0 \
+  --width 1280 \
+  --height 720 \
+  --angle 0.0 \
+  --capture "target/render-parity/current/animals_a_l_01.png"
+```
 
 ## Ограничения
 

crates/render-demo/src/main.rs

@@ -1,7 +1,7 @@
 use glow::HasContext as _;
 use render_core::{build_render_mesh, compute_bounds};
 use render_demo::load_model_from_archive;
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 use std::time::Instant;
 
 struct Args {
@@ -9,6 +9,11 @@ struct Args {
     model: Option<String>,
     lod: usize,
     group: usize,
+    width: u32,
+    height: u32,
+    capture: Option<PathBuf>,
+    angle: Option<f32>,
+    spin_rate: f32,
 }
 
 fn parse_args() -> Result<Args, String> {
@@ -16,6 +21,11 @@ fn parse_args() -> Result<Args, String> {
     let mut model = None;
     let mut lod = 0usize;
     let mut group = 0usize;
+    let mut width = 1280u32;
+    let mut height = 720u32;
+    let mut capture = None;
+    let mut angle = None;
+    let mut spin_rate = 0.35f32;
 
     let mut it = std::env::args().skip(1);
     while let Some(arg) = it.next() {
@@ -48,6 +58,52 @@ fn parse_args() -> Result<Args, String> {
                     .parse::<usize>()
                     .map_err(|_| String::from("invalid --group value"))?;
             }
+            "--width" => {
+                let value = it
+                    .next()
+                    .ok_or_else(|| String::from("missing value for --width"))?;
+                width = value
+                    .parse::<u32>()
+                    .map_err(|_| String::from("invalid --width value"))?;
+                if width == 0 {
+                    return Err(String::from("--width must be > 0"));
+                }
+            }
+            "--height" => {
+                let value = it
+                    .next()
+                    .ok_or_else(|| String::from("missing value for --height"))?;
+                height = value
+                    .parse::<u32>()
+                    .map_err(|_| String::from("invalid --height value"))?;
+                if height == 0 {
+                    return Err(String::from("--height must be > 0"));
+                }
+            }
+            "--capture" => {
+                let value = it
+                    .next()
+                    .ok_or_else(|| String::from("missing value for --capture"))?;
+                capture = Some(PathBuf::from(value));
+            }
+            "--angle" => {
+                let value = it
+                    .next()
+                    .ok_or_else(|| String::from("missing value for --angle"))?;
+                angle = Some(
+                    value
+                        .parse::<f32>()
+                        .map_err(|_| String::from("invalid --angle value"))?,
+                );
+            }
+            "--spin-rate" => {
+                let value = it
+                    .next()
+                    .ok_or_else(|| String::from("missing value for --spin-rate"))?;
+                spin_rate = value
+                    .parse::<f32>()
+                    .map_err(|_| String::from("invalid --spin-rate value"))?;
+            }
             "--help" | "-h" => {
                 print_help();
                 std::process::exit(0);
@@ -64,11 +120,19 @@ fn parse_args() -> Result<Args, String> {
         model,
         lod,
         group,
+        width,
+        height,
+        capture,
+        angle,
+        spin_rate,
     })
 }
 
 fn print_help() {
-    eprintln!("parkan-render-demo --archive <path> [--model <name.msh>] [--lod N] [--group N]");
+    eprintln!(
+        "parkan-render-demo --archive <path> [--model <name.msh>] [--lod N] [--group N] [--width W] [--height H]"
+    );
+    eprintln!("                  [--capture <out.png>] [--angle RAD] [--spin-rate RAD_PER_SEC]");
 }
 
 fn main() {
@@ -81,25 +145,29 @@ fn main() {
         }
     };
 
-    let model = match load_model_from_archive(&args.archive, args.model.as_deref()) {
+    if let Err(err) = run(args) {
-        Ok(v) => v,
+        eprintln!("{err}");
-        Err(err) => {
-            eprintln!("failed to load model: {err:?}");
         std::process::exit(1);
     }
-    };
+}
+
+fn run(args: Args) -> Result<(), String> {
+    let model = load_model_from_archive(&args.archive, args.model.as_deref()).map_err(|err| {
+        format!(
+            "failed to load model from archive {}: {err:?}",
+            args.archive.display()
+        )
+    })?;
 
     let mesh = build_render_mesh(&model, args.lod, args.group);
     if mesh.vertices.is_empty() {
-        eprintln!(
+        return Err(format!(
             "model has no renderable triangles for lod={} group={}",
             args.lod, args.group
-        );
+        ));
-        std::process::exit(1);
     }
     let Some((bounds_min, bounds_max)) = compute_bounds(&mesh.vertices) else {
-        eprintln!("failed to compute mesh bounds");
+        return Err(String::from("failed to compute mesh bounds"));
-        std::process::exit(1);
     };
 
     let center = [
@@ -116,8 +184,10 @@ fn main() {
         (extent[0] * extent[0] + extent[1] * extent[1] + extent[2] * extent[2]).sqrt() * 0.5;
     let camera_distance = (radius * 2.5).max(2.0);
 
-    let sdl = sdl2::init().expect("failed to init SDL2");
+    let sdl = sdl2::init().map_err(|err| format!("failed to init SDL2: {err}"))?;
-    let video = sdl.video().expect("failed to init SDL2 video");
+    let video = sdl
+        .video()
+        .map_err(|err| format!("failed to init SDL2 video: {err}"))?;
 
     {
         let gl_attr = video.gl_attr();
@@ -127,20 +197,32 @@ fn main() {
         gl_attr.set_double_buffer(true);
     }
 
-    let window = video
+    let mut window_builder = video.window(
-        .window("Parkan Render Demo (SDL2 + OpenGL ES 2.0)", 1280, 720)
+        "Parkan Render Demo (SDL2 + OpenGL ES 2.0)",
-        .opengl()
+        args.width,
-        .resizable()
+        args.height,
+    );
+    window_builder.opengl();
+    if args.capture.is_some() {
+        window_builder.hidden();
+    } else {
+        window_builder.resizable();
+    }
+    let window = window_builder
         .build()
-        .expect("failed to create window");
+        .map_err(|err| format!("failed to create window: {err}"))?;
 
     let gl_ctx = window
         .gl_create_context()
-        .expect("failed to create OpenGL context");
+        .map_err(|err| format!("failed to create OpenGL context: {err}"))?;
     window
         .gl_make_current(&gl_ctx)
-        .expect("failed to make GL context current");
+        .map_err(|err| format!("failed to make GL context current: {err}"))?;
-    let _ = video.gl_set_swap_interval(1);
+    let _ = if args.capture.is_some() {
+        video.gl_set_swap_interval(0)
+    } else {
+        video.gl_set_swap_interval(1)
+    };
 
     let mut vertices_flat = Vec::with_capacity(mesh.vertices.len() * 3);
     for pos in &mesh.vertices {
@@ -151,12 +233,12 @@ fn main() {
         glow::Context::from_loader_function(|name| video.gl_get_proc_address(name) as *const _)
     };
 
-    let program = unsafe { create_program(&gl).expect("failed to create shader program") };
+    let program = unsafe { create_program(&gl)? };
     let u_mvp = unsafe { gl.get_uniform_location(program, "u_mvp") };
-    let a_pos = unsafe { gl.get_attrib_location(program, "a_pos") };
+    let a_pos = unsafe { gl.get_attrib_location(program, "a_pos") }
-    let a_pos = a_pos.expect("shader attribute a_pos is missing");
+        .ok_or_else(|| String::from("shader attribute a_pos is missing"))?;
 
-    let vbo = unsafe { gl.create_buffer().expect("failed to create VBO") };
+    let vbo = unsafe { gl.create_buffer().map_err(|e| e.to_string())? };
     unsafe {
         gl.bind_buffer(glow::ARRAY_BUFFER, Some(vbo));
         gl.buffer_data_u8_slice(
@@ -167,7 +249,95 @@ fn main() {
         gl.bind_buffer(glow::ARRAY_BUFFER, None);
     }
 
-    let mut events = sdl.event_pump().expect("failed to get SDL event pump");
+    let result = if let Some(capture_path) = args.capture.as_ref() {
+        run_capture(
+            &gl,
+            program,
+            u_mvp.as_ref(),
+            a_pos,
+            vbo,
+            mesh.vertices.len(),
+            &args,
+            center,
+            camera_distance,
+            capture_path,
+        )
+    } else {
+        run_interactive(
+            &sdl,
+            &window,
+            &gl,
+            program,
+            u_mvp.as_ref(),
+            a_pos,
+            vbo,
+            mesh.vertices.len(),
+            &args,
+            center,
+            camera_distance,
+        )
+    };
+
+    unsafe {
+        gl.delete_buffer(vbo);
+        gl.delete_program(program);
+    }
+
+    result
+}
+
+#[allow(clippy::too_many_arguments)]
+fn run_capture(
+    gl: &glow::Context,
+    program: glow::NativeProgram,
+    u_mvp: Option<&glow::NativeUniformLocation>,
+    a_pos: u32,
+    vbo: glow::NativeBuffer,
+    vertex_count: usize,
+    args: &Args,
+    center: [f32; 3],
+    camera_distance: f32,
+    capture_path: &Path,
+) -> Result<(), String> {
+    let angle = args.angle.unwrap_or(0.0);
+    let mvp = compute_mvp(args.width, args.height, center, camera_distance, angle);
+    unsafe {
+        draw_frame(
+            gl,
+            program,
+            u_mvp,
+            a_pos,
+            vbo,
+            vertex_count,
+            args.width,
+            args.height,
+            &mvp,
+        );
+    }
+    let mut rgba = unsafe { read_pixels_rgba(gl, args.width, args.height)? };
+    flip_image_y_rgba(&mut rgba, args.width as usize, args.height as usize);
+    save_png(capture_path, args.width, args.height, rgba)?;
+    println!("captured frame to {}", capture_path.display());
+    Ok(())
+}
+
+#[allow(clippy::too_many_arguments)]
+fn run_interactive(
+    sdl: &sdl2::Sdl,
+    window: &sdl2::video::Window,
+    gl: &glow::Context,
+    program: glow::NativeProgram,
+    u_mvp: Option<&glow::NativeUniformLocation>,
+    a_pos: u32,
+    vbo: glow::NativeBuffer,
+    vertex_count: usize,
+    args: &Args,
+    center: [f32; 3],
+    camera_distance: f32,
+) -> Result<(), String> {
+    let mut events = sdl
+        .event_pump()
+        .map_err(|err| format!("failed to get SDL event pump: {err}"))?;
     let start = Instant::now();
 
     'main_loop: loop {
@@ -182,26 +352,62 @@ fn main() {
             }
         }
 
-        let elapsed = start.elapsed().as_secs_f32();
         let (w, h) = window.size();
-        let aspect = (w as f32 / (h.max(1) as f32)).max(0.01);
+        let angle = args
+            .angle
+            .unwrap_or(start.elapsed().as_secs_f32() * args.spin_rate);
+        let mvp = compute_mvp(w, h, center, camera_distance, angle);
 
+        unsafe {
+            draw_frame(gl, program, u_mvp, a_pos, vbo, vertex_count, w, h, &mvp);
+        }
+        window.gl_swap_window();
+    }
+
+    Ok(())
+}
+
+fn compute_mvp(
+    width: u32,
+    height: u32,
+    center: [f32; 3],
+    camera_distance: f32,
+    angle_rad: f32,
+) -> [f32; 16] {
+    let aspect = (width as f32 / (height.max(1) as f32)).max(0.01);
     let proj = mat4_perspective(60.0_f32.to_radians(), aspect, 0.01, camera_distance * 10.0);
     let view = mat4_translation(0.0, 0.0, -camera_distance);
     let center_shift = mat4_translation(-center[0], -center[1], -center[2]);
-        let rot = mat4_rotation_y(elapsed * 0.35);
+    let rot = mat4_rotation_y(angle_rad);
     let model_m = mat4_mul(&rot, &center_shift);
     let vp = mat4_mul(&view, &model_m);
-        let mvp = mat4_mul(&proj, &vp);
+    mat4_mul(&proj, &vp)
+}
 
-        unsafe {
+#[allow(clippy::too_many_arguments)]
-            gl.viewport(0, 0, w as i32, h as i32);
+unsafe fn draw_frame(
+    gl: &glow::Context,
+    program: glow::NativeProgram,
+    u_mvp: Option<&glow::NativeUniformLocation>,
+    a_pos: u32,
+    vbo: glow::NativeBuffer,
+    vertex_count: usize,
+    width: u32,
+    height: u32,
+    mvp: &[f32; 16],
+) {
+    gl.viewport(
+        0,
+        0,
+        width.min(i32::MAX as u32) as i32,
+        height.min(i32::MAX as u32) as i32,
+    );
     gl.enable(glow::DEPTH_TEST);
     gl.clear_color(0.06, 0.08, 0.12, 1.0);
     gl.clear(glow::COLOR_BUFFER_BIT | glow::DEPTH_BUFFER_BIT);
 
     gl.use_program(Some(program));
-            gl.uniform_matrix_4_f32_slice(u_mvp.as_ref(), false, &mvp);
+    gl.uniform_matrix_4_f32_slice(u_mvp, false, mvp);
 
     gl.bind_buffer(glow::ARRAY_BUFFER, Some(vbo));
     gl.enable_vertex_attrib_array(a_pos);
@@ -209,20 +415,61 @@ fn main() {
     gl.draw_arrays(
         glow::TRIANGLES,
         0,
-                i32::try_from(mesh.vertices.len()).unwrap_or(i32::MAX),
+        vertex_count.min(i32::MAX as usize) as i32,
     );
     gl.disable_vertex_attrib_array(a_pos);
     gl.bind_buffer(glow::ARRAY_BUFFER, None);
     gl.use_program(None);
 }
 
-        window.gl_swap_window();
+unsafe fn read_pixels_rgba(gl: &glow::Context, width: u32, height: u32) -> Result<Vec<u8>, String> {
+    let pixel_count = usize::try_from(width)
+        .ok()
+        .and_then(|w| usize::try_from(height).ok().map(|h| w.saturating_mul(h)))
+        .ok_or_else(|| String::from("frame dimensions are too large"))?;
+    let mut pixels = vec![0u8; pixel_count.saturating_mul(4)];
+    gl.read_pixels(
+        0,
+        0,
+        width.min(i32::MAX as u32) as i32,
+        height.min(i32::MAX as u32) as i32,
+        glow::RGBA,
+        glow::UNSIGNED_BYTE,
+        glow::PixelPackData::Slice(Some(pixels.as_mut_slice())),
+    );
+    Ok(pixels)
 }
 
-    unsafe {
+fn flip_image_y_rgba(rgba: &mut [u8], width: usize, height: usize) {
-        gl.delete_buffer(vbo);
+    let stride = width.saturating_mul(4);
-        gl.delete_program(program);
+    if stride == 0 {
+        return;
     }
+    for y in 0..(height / 2) {
+        let top = y * stride;
+        let bottom = (height - 1 - y) * stride;
+        for i in 0..stride {
+            rgba.swap(top + i, bottom + i);
+        }
+    }
+}
+
+fn save_png(path: &Path, width: u32, height: u32, rgba: Vec<u8>) -> Result<(), String> {
+    if let Some(parent) = path.parent() {
+        if !parent.as_os_str().is_empty() {
+            std::fs::create_dir_all(parent).map_err(|err| {
+                format!(
+                    "failed to create output directory {}: {err}",
+                    parent.display()
+                )
+            })?;
+        }
+    }
+    let image = image::RgbaImage::from_raw(width, height, rgba)
+        .ok_or_else(|| String::from("failed to build image from framebuffer bytes"))?;
+    image
+        .save(path)
+        .map_err(|err| format!("failed to save PNG {}: {err}", path.display()))
 }
 
 unsafe fn create_program(gl: &glow::Context) -> Result<glow::NativeProgram, String> {

crates/render-parity/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "render-parity"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+image = { version = "0.25", default-features = false, features = ["png"] }
+serde = { version = "1", features = ["derive"] }
+toml = "0.8"

crates/render-parity/README.md

@@ -0,0 +1,16 @@
+# render-parity
+
+Deterministic frame-diff runner for `parkan-render-demo`.
+
+Usage:
+
+```bash
+cargo run -p render-parity -- \
+  --manifest parity/cases.toml \
+  --output-dir target/render-parity/current
+```
+
+Options:
+
+- `--demo-bin <path>`: use prebuilt `parkan-render-demo` binary instead of `cargo run`.
+- `--keep-going`: continue all cases even after failures.

crates/render-parity/src/lib.rs

@@ -0,0 +1,212 @@
+use image::{ImageBuffer, Rgba, RgbaImage};
+use serde::Deserialize;
+
+#[derive(Debug, Clone, Deserialize, Default)]
+pub struct ManifestMeta {
+    pub width: Option<u32>,
+    pub height: Option<u32>,
+    pub lod: Option<usize>,
+    pub group: Option<usize>,
+    pub angle: Option<f32>,
+    pub diff_threshold: Option<u8>,
+    pub max_mean_abs: Option<f32>,
+    pub max_changed_ratio: Option<f32>,
+}
+
+#[derive(Debug, Clone, Deserialize)]
+pub struct CaseSpec {
+    pub id: String,
+    pub archive: String,
+    pub model: Option<String>,
+    pub reference: String,
+    pub width: Option<u32>,
+    pub height: Option<u32>,
+    pub lod: Option<usize>,
+    pub group: Option<usize>,
+    pub angle: Option<f32>,
+    pub diff_threshold: Option<u8>,
+    pub max_mean_abs: Option<f32>,
+    pub max_changed_ratio: Option<f32>,
+}
+
+#[derive(Debug, Clone, Deserialize)]
+pub struct ParityManifest {
+    #[serde(default)]
+    pub meta: ManifestMeta,
+    #[serde(rename = "case", default)]
+    pub cases: Vec<CaseSpec>,
+}
+
+#[derive(Debug, Clone)]
+pub struct DiffMetrics {
+    pub width: u32,
+    pub height: u32,
+    pub mean_abs: f32,
+    pub max_abs: u8,
+    pub changed_pixels: u64,
+    pub changed_ratio: f32,
+}
+
+pub fn compare_images(
+    reference: &RgbaImage,
+    actual: &RgbaImage,
+    diff_threshold: u8,
+) -> Result<DiffMetrics, String> {
+    let (rw, rh) = reference.dimensions();
+    let (aw, ah) = actual.dimensions();
+    if rw != aw || rh != ah {
+        return Err(format!(
+            "image size mismatch: reference={}x{}, actual={}x{}",
+            rw, rh, aw, ah
+        ));
+    }
+
+    let mut diff_sum = 0u64;
+    let mut max_abs = 0u8;
+    let mut changed_pixels = 0u64;
+    let pixel_count = u64::from(rw).saturating_mul(u64::from(rh));
+
+    for (ref_px, act_px) in reference.pixels().zip(actual.pixels()) {
+        let mut pixel_changed = false;
+        for chan in 0..3 {
+            let a = i16::from(ref_px[chan]);
+            let b = i16::from(act_px[chan]);
+            let diff = (a - b).unsigned_abs() as u8;
+            diff_sum = diff_sum.saturating_add(u64::from(diff));
+            if diff > max_abs {
+                max_abs = diff;
+            }
+            if diff > diff_threshold {
+                pixel_changed = true;
+            }
+        }
+        if pixel_changed {
+            changed_pixels = changed_pixels.saturating_add(1);
+        }
+    }
+
+    let channels = pixel_count.saturating_mul(3);
+    let mean_abs = if channels == 0 {
+        0.0
+    } else {
+        diff_sum as f32 / channels as f32
+    };
+    let changed_ratio = if pixel_count == 0 {
+        0.0
+    } else {
+        changed_pixels as f32 / pixel_count as f32
+    };
+
+    Ok(DiffMetrics {
+        width: rw,
+        height: rh,
+        mean_abs,
+        max_abs,
+        changed_pixels,
+        changed_ratio,
+    })
+}
+
+pub fn build_diff_image(reference: &RgbaImage, actual: &RgbaImage) -> Result<RgbaImage, String> {
+    let (rw, rh) = reference.dimensions();
+    let (aw, ah) = actual.dimensions();
+    if rw != aw || rh != ah {
+        return Err(format!(
+            "image size mismatch: reference={}x{}, actual={}x{}",
+            rw, rh, aw, ah
+        ));
+    }
+
+    let mut out: ImageBuffer<Rgba<u8>, Vec<u8>> = ImageBuffer::new(rw, rh);
+    for (dst, (ref_px, act_px)) in out
+        .pixels_mut()
+        .zip(reference.pixels().zip(actual.pixels()))
+    {
+        let dr = (i16::from(ref_px[0]) - i16::from(act_px[0])).unsigned_abs() as u8;
+        let dg = (i16::from(ref_px[1]) - i16::from(act_px[1])).unsigned_abs() as u8;
+        let db = (i16::from(ref_px[2]) - i16::from(act_px[2])).unsigned_abs() as u8;
+        *dst = Rgba([dr, dg, db, 255]);
+    }
+    Ok(out)
+}
+
+pub fn evaluate_metrics(
+    metrics: &DiffMetrics,
+    max_mean_abs: f32,
+    max_changed_ratio: f32,
+) -> Vec<String> {
+    let mut violations = Vec::new();
+    if metrics.mean_abs > max_mean_abs {
+        violations.push(format!(
+            "mean_abs {:.4} > allowed {:.4}",
+            metrics.mean_abs, max_mean_abs
+        ));
+    }
+    if metrics.changed_ratio > max_changed_ratio {
+        violations.push(format!(
+            "changed_ratio {:.4}% > allowed {:.4}%",
+            metrics.changed_ratio * 100.0,
+            max_changed_ratio * 100.0
+        ));
+    }
+    violations
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn solid(w: u32, h: u32, r: u8, g: u8, b: u8) -> RgbaImage {
+        let mut img = RgbaImage::new(w, h);
+        for px in img.pixels_mut() {
+            *px = Rgba([r, g, b, 255]);
+        }
+        img
+    }
+
+    #[test]
+    fn compare_identical_images() {
+        let ref_img = solid(4, 3, 10, 20, 30);
+        let act_img = solid(4, 3, 10, 20, 30);
+        let metrics = compare_images(&ref_img, &act_img, 2).expect("comparison must succeed");
+        assert_eq!(metrics.width, 4);
+        assert_eq!(metrics.height, 3);
+        assert_eq!(metrics.max_abs, 0);
+        assert_eq!(metrics.changed_pixels, 0);
+        assert_eq!(metrics.mean_abs, 0.0);
+        assert_eq!(metrics.changed_ratio, 0.0);
+    }
+
+    #[test]
+    fn compare_detects_changes_and_thresholds() {
+        let mut ref_img = solid(2, 2, 100, 100, 100);
+        let mut act_img = solid(2, 2, 100, 100, 100);
+        ref_img.put_pixel(1, 1, Rgba([120, 100, 100, 255]));
+        act_img.put_pixel(1, 1, Rgba([100, 100, 100, 255]));
+
+        let metrics = compare_images(&ref_img, &act_img, 5).expect("comparison must succeed");
+        assert_eq!(metrics.max_abs, 20);
+        assert_eq!(metrics.changed_pixels, 1);
+        assert!((metrics.changed_ratio - 0.25).abs() < 1e-6);
+        assert!(metrics.mean_abs > 0.0);
+
+        let violations = evaluate_metrics(&metrics, 2.0, 0.20);
+        assert_eq!(violations.len(), 1);
+        assert!(violations[0].contains("changed_ratio"));
+    }
+
+    #[test]
+    fn build_diff_image_returns_per_channel_abs_diff() {
+        let mut ref_img = solid(1, 1, 100, 150, 200);
+        let mut act_img = solid(1, 1, 90, 180, 170);
+        ref_img.put_pixel(0, 0, Rgba([100, 150, 200, 255]));
+        act_img.put_pixel(0, 0, Rgba([90, 180, 170, 255]));
+
+        let diff = build_diff_image(&ref_img, &act_img).expect("diff image must build");
+        let px = diff.get_pixel(0, 0);
+        assert_eq!(px[0], 10);
+        assert_eq!(px[1], 30);
+        assert_eq!(px[2], 30);
+        assert_eq!(px[3], 255);
+    }
+}

crates/render-parity/src/main.rs

@@ -0,0 +1,405 @@
+use image::RgbaImage;
+use render_parity::{
+    build_diff_image, compare_images, evaluate_metrics, CaseSpec, ManifestMeta, ParityManifest,
+};
+use std::fs;
+use std::path::{Path, PathBuf};
+use std::process::Command;
+
+const DEFAULT_MANIFEST: &str = "parity/cases.toml";
+const DEFAULT_OUTPUT_DIR: &str = "target/render-parity/current";
+const DEFAULT_WIDTH: u32 = 1280;
+const DEFAULT_HEIGHT: u32 = 720;
+const DEFAULT_LOD: usize = 0;
+const DEFAULT_GROUP: usize = 0;
+const DEFAULT_ANGLE: f32 = 0.0;
+const DEFAULT_DIFF_THRESHOLD: u8 = 8;
+const DEFAULT_MAX_MEAN_ABS: f32 = 2.0;
+const DEFAULT_MAX_CHANGED_RATIO: f32 = 0.01;
+
+struct Args {
+    manifest: PathBuf,
+    output_dir: PathBuf,
+    demo_bin: Option<PathBuf>,
+    keep_going: bool,
+}
+
+#[derive(Debug, Clone)]
+struct EffectiveCase {
+    id: String,
+    archive: PathBuf,
+    model: Option<String>,
+    reference: PathBuf,
+    width: u32,
+    height: u32,
+    lod: usize,
+    group: usize,
+    angle: f32,
+    diff_threshold: u8,
+    max_mean_abs: f32,
+    max_changed_ratio: f32,
+}
+
+fn main() {
+    let args = match parse_args() {
+        Ok(v) => v,
+        Err(err) => {
+            eprintln!("{err}");
+            print_help();
+            std::process::exit(2);
+        }
+    };
+
+    if let Err(err) = run(args) {
+        eprintln!("{err}");
+        std::process::exit(1);
+    }
+}
+
+fn parse_args() -> Result<Args, String> {
+    let mut manifest = PathBuf::from(DEFAULT_MANIFEST);
+    let mut output_dir = PathBuf::from(DEFAULT_OUTPUT_DIR);
+    let mut demo_bin = None;
+    let mut keep_going = false;
+
+    let mut it = std::env::args().skip(1);
+    while let Some(arg) = it.next() {
+        match arg.as_str() {
+            "--manifest" => {
+                let value = it
+                    .next()
+                    .ok_or_else(|| String::from("missing value for --manifest"))?;
+                manifest = PathBuf::from(value);
+            }
+            "--output-dir" => {
+                let value = it
+                    .next()
+                    .ok_or_else(|| String::from("missing value for --output-dir"))?;
+                output_dir = PathBuf::from(value);
+            }
+            "--demo-bin" => {
+                let value = it
+                    .next()
+                    .ok_or_else(|| String::from("missing value for --demo-bin"))?;
+                demo_bin = Some(PathBuf::from(value));
+            }
+            "--keep-going" => {
+                keep_going = true;
+            }
+            "--help" | "-h" => {
+                print_help();
+                std::process::exit(0);
+            }
+            other => {
+                return Err(format!("unknown argument: {other}"));
+            }
+        }
+    }
+
+    Ok(Args {
+        manifest,
+        output_dir,
+        demo_bin,
+        keep_going,
+    })
+}
+
+fn print_help() {
+    eprintln!(
+        "render-parity [--manifest <cases.toml>] [--output-dir <dir>] [--demo-bin <path>] [--keep-going]"
+    );
+    eprintln!("  --manifest    path to parity manifest (default: {DEFAULT_MANIFEST})");
+    eprintln!("  --output-dir  where current renders and diff images are written");
+    eprintln!("  --demo-bin    prebuilt parkan-render-demo binary path");
+    eprintln!("  --keep-going  continue all cases even after failures");
+}
+
+fn run(args: Args) -> Result<(), String> {
+    let workspace = workspace_root()?;
+    let manifest_path = resolve_path(&workspace, &args.manifest);
+    let output_dir = resolve_path(&workspace, &args.output_dir);
+    let demo_bin = args
+        .demo_bin
+        .as_ref()
+        .map(|path| resolve_path(&workspace, path));
+
+    let manifest_raw = fs::read_to_string(&manifest_path)
+        .map_err(|err| format!("failed to read manifest {}: {err}", manifest_path.display()))?;
+    let manifest: ParityManifest = toml::from_str(&manifest_raw).map_err(|err| {
+        format!(
+            "failed to parse manifest {}: {err}",
+            manifest_path.display()
+        )
+    })?;
+
+    if manifest.cases.is_empty() {
+        println!(
+            "render-parity: no cases in {} (nothing to validate)",
+            manifest_path.display()
+        );
+        return Ok(());
+    }
+
+    fs::create_dir_all(&output_dir).map_err(|err| {
+        format!(
+            "failed to create output directory {}: {err}",
+            output_dir.display()
+        )
+    })?;
+
+    let manifest_dir = manifest_path
+        .parent()
+        .map(Path::to_path_buf)
+        .unwrap_or_else(|| workspace.clone());
+
+    let mut failed_cases = 0usize;
+    for case in &manifest.cases {
+        let effective = make_effective_case(&manifest.meta, case, &manifest_dir)?;
+        let case_file = output_dir.join(format!("{}.png", sanitize_case_id(&effective.id)));
+        let diff_file = output_dir
+            .join("diff")
+            .join(format!("{}.png", sanitize_case_id(&effective.id)));
+
+        let run_res = run_single_case(
+            &workspace, // ensure `cargo run` executes from workspace root
+            demo_bin.as_deref(),
+            &effective,
+            &case_file,
+            &diff_file,
+        );
+
+        match run_res {
+            Ok(()) => {}
+            Err(err) => {
+                failed_cases = failed_cases.saturating_add(1);
+                eprintln!("[FAIL] {}: {}", effective.id, err);
+                if !args.keep_going {
+                    break;
+                }
+            }
+        }
+    }
+
+    if failed_cases > 0 {
+        return Err(format!(
+            "render-parity failed: {} case(s) did not match reference frames",
+            failed_cases
+        ));
+    }
+
+    println!("render-parity: all cases passed");
+    Ok(())
+}
+
+fn run_single_case(
+    workspace: &Path,
+    demo_bin: Option<&Path>,
+    case: &EffectiveCase,
+    case_file: &Path,
+    diff_file: &Path,
+) -> Result<(), String> {
+    run_render_capture(workspace, demo_bin, case, case_file)?;
+
+    let reference = load_rgba(&case.reference)?;
+    let actual = load_rgba(case_file)?;
+    let metrics = compare_images(&reference, &actual, case.diff_threshold)?;
+    let violations = evaluate_metrics(&metrics, case.max_mean_abs, case.max_changed_ratio);
+
+    if violations.is_empty() {
+        println!(
+            "[OK] {} mean_abs={:.4} changed={:.4}% max_abs={} ({}x{})",
+            case.id,
+            metrics.mean_abs,
+            metrics.changed_ratio * 100.0,
+            metrics.max_abs,
+            metrics.width,
+            metrics.height
+        );
+        return Ok(());
+    }
+
+    if let Some(parent) = diff_file.parent() {
+        fs::create_dir_all(parent).map_err(|err| {
+            format!(
+                "failed to create diff output directory {}: {err}",
+                parent.display()
+            )
+        })?;
+    }
+    let diff = build_diff_image(&reference, &actual)?;
+    diff.save(diff_file)
+        .map_err(|err| format!("failed to save diff image {}: {err}", diff_file.display()))?;
+
+    let mut details = String::new();
+    for item in violations {
+        if !details.is_empty() {
+            details.push_str("; ");
+        }
+        details.push_str(&item);
+    }
+    Err(format!(
+        "{} | diff={} | mean_abs={:.4}, changed={:.4}% ({} px), max_abs={}",
+        details,
+        diff_file.display(),
+        metrics.mean_abs,
+        metrics.changed_ratio * 100.0,
+        metrics.changed_pixels,
+        metrics.max_abs
+    ))
+}
+
+fn run_render_capture(
+    workspace: &Path,
+    demo_bin: Option<&Path>,
+    case: &EffectiveCase,
+    out_path: &Path,
+) -> Result<(), String> {
+    if let Some(parent) = out_path.parent() {
+        fs::create_dir_all(parent).map_err(|err| {
+            format!(
+                "failed to create capture directory {}: {err}",
+                parent.display()
+            )
+        })?;
+    }
+
+    let mut cmd = if let Some(bin) = demo_bin {
+        Command::new(bin)
+    } else {
+        let mut command = Command::new("cargo");
+        command.args(["run", "-p", "render-demo", "--features", "demo", "--"]);
+        command
+    };
+
+    cmd.current_dir(workspace)
+        .arg("--archive")
+        .arg(&case.archive)
+        .arg("--lod")
+        .arg(case.lod.to_string())
+        .arg("--group")
+        .arg(case.group.to_string())
+        .arg("--width")
+        .arg(case.width.to_string())
+        .arg("--height")
+        .arg(case.height.to_string())
+        .arg("--angle")
+        .arg(case.angle.to_string())
+        .arg("--capture")
+        .arg(out_path);
+
+    if let Some(model) = case.model.as_deref() {
+        cmd.arg("--model").arg(model);
+    }
+
+    let output = cmd.output().map_err(|err| {
+        let mode = if demo_bin.is_some() {
+            "parkan-render-demo"
+        } else {
+            "cargo run -p render-demo"
+        };
+        format!("failed to execute {} for case {}: {err}", mode, case.id)
+    })?;
+    if !output.status.success() {
+        let stdout = String::from_utf8_lossy(&output.stdout);
+        let stderr = String::from_utf8_lossy(&output.stderr);
+        return Err(format!(
+            "render command exited with status {:?}\nstdout:\n{}\nstderr:\n{}",
+            output.status.code(),
+            stdout,
+            stderr
+        ));
+    }
+
+    Ok(())
+}
+
+fn load_rgba(path: &Path) -> Result<RgbaImage, String> {
+    image::open(path)
+        .map_err(|err| format!("failed to load image {}: {err}", path.display()))
+        .map(|img| img.to_rgba8())
+}
+
+fn make_effective_case(
+    meta: &ManifestMeta,
+    case: &CaseSpec,
+    manifest_dir: &Path,
+) -> Result<EffectiveCase, String> {
+    let width = case.width.or(meta.width).unwrap_or(DEFAULT_WIDTH);
+    let height = case.height.or(meta.height).unwrap_or(DEFAULT_HEIGHT);
+    if width == 0 || height == 0 {
+        return Err(format!(
+            "case '{}' has invalid dimensions {}x{}",
+            case.id, width, height
+        ));
+    }
+
+    let archive = resolve_path(manifest_dir, Path::new(&case.archive));
+    let reference = resolve_path(manifest_dir, Path::new(&case.reference));
+    if !archive.is_file() {
+        return Err(format!(
+            "case '{}' archive not found: {}",
+            case.id,
+            archive.display()
+        ));
+    }
+    if !reference.is_file() {
+        return Err(format!(
+            "case '{}' reference frame not found: {}",
+            case.id,
+            reference.display()
+        ));
+    }
+
+    Ok(EffectiveCase {
+        id: case.id.clone(),
+        archive,
+        model: case.model.clone(),
+        reference,
+        width,
+        height,
+        lod: case.lod.or(meta.lod).unwrap_or(DEFAULT_LOD),
+        group: case.group.or(meta.group).unwrap_or(DEFAULT_GROUP),
+        angle: case.angle.or(meta.angle).unwrap_or(DEFAULT_ANGLE),
+        diff_threshold: case
+            .diff_threshold
+            .or(meta.diff_threshold)
+            .unwrap_or(DEFAULT_DIFF_THRESHOLD),
+        max_mean_abs: case
+            .max_mean_abs
+            .or(meta.max_mean_abs)
+            .unwrap_or(DEFAULT_MAX_MEAN_ABS),
+        max_changed_ratio: case
+            .max_changed_ratio
+            .or(meta.max_changed_ratio)
+            .unwrap_or(DEFAULT_MAX_CHANGED_RATIO),
+    })
+}
+
+fn sanitize_case_id(id: &str) -> String {
+    id.chars()
+        .map(|c| {
+            if c.is_ascii_alphanumeric() || c == '-' || c == '_' {
+                c
+            } else {
+                '_'
+            }
+        })
+        .collect()
+}
+
+fn workspace_root() -> Result<PathBuf, String> {
+    let root = Path::new(env!("CARGO_MANIFEST_DIR"))
+        .join("..")
+        .join("..")
+        .canonicalize()
+        .map_err(|err| format!("failed to resolve workspace root: {err}"))?;
+    Ok(root)
+}
+
+fn resolve_path(base: &Path, path: &Path) -> PathBuf {
+    if path.is_absolute() {
+        path.to_path_buf()
+    } else {
+        base.join(path)
+    }
+}

docs/specs/render-parity.md

@@ -0,0 +1,77 @@
+# Рендер-паритет (кадровый diff)
+
+Документ описывает процесс проверки соответствия рендера:  
+`оригинальный движок -> эталонный кадр -> render-demo -> diff-метрики`.
+
+## Цель
+
+- Зафиксировать объективный критерий "паритет достигнут / не достигнут".
+- Убрать субъективную визуальную оценку "похоже/не похоже".
+- Дать CI-проверку, которая ловит регрессии сразу после коммита.
+
+## Единица проверки
+
+Один тест-кейс = один объект (одна модель) + фиксированная конфигурация:
+
+- архив ресурса;
+- имя модели;
+- `lod`;
+- `group`;
+- размер кадра (`width`, `height`);
+- угол камеры (`angle`);
+- PNG-эталон из оригинального рендера.
+
+## Инварианты детерминизма
+
+Для корректного сравнения кадры должны быть сняты в одинаковых условиях:
+
+- одинаковый FOV и расстояние камеры до объекта;
+- одинаковый clear-color/фон;
+- одинаковые `lod/group`;
+- фиксированный угол (`angle`), без анимации;
+- фиксированное разрешение.
+
+## Метрики сравнения
+
+Сравнение выполняется по RGB-каналам:
+
+- `mean_abs`: средняя абсолютная разница канала (0..255);
+- `max_abs`: максимальная разница канала;
+- `changed_ratio`: доля пикселей, где хотя бы один канал превышает `diff_threshold`.
+
+Кейс считается пройденным, если:
+
+- `mean_abs <= max_mean_abs`;
+- `changed_ratio <= max_changed_ratio`.
+
+## Конфигурация кейсов
+
+Файл: `parity/cases.toml`.
+
+- секция `[meta]`: глобальные дефолты;
+- `[[case]]`: параметры конкретной модели и путь к эталонному PNG.
+
+Эталонные кадры хранятся в `parity/reference/`.
+
+## Локальный запуск
+
+```bash
+cargo run -p render-parity -- \
+  --manifest parity/cases.toml \
+  --output-dir target/render-parity/current
+```
+
+При расхождении утилита пишет diff-изображение в:
+
+- `target/render-parity/current/diff/<case>.png`
+
+## CI-модель
+
+CI запускает `render-parity` на каждом push/PR:
+
+1. собирает `parkan-render-demo`;
+2. прогоняет кейсы из `cases.toml`;
+3. при падении публикует текущие кадры и diff как артефакт.
+
+Важно: оригинальный движок в CI обычно не запускается.  
+Эталонные PNG снимаются офлайн и версионируются в репозитории.

mkdocs.yml

@@ -39,6 +39,7 @@ nav:
       - Network system: specs/network.md
       - NRes / RsLi: specs/nres.md
       - Render pipeline: specs/render.md
+      - Render parity: specs/render-parity.md
       - Runtime pointer: specs/runtime-pipeline.md
       - Sound system: specs/sound.md
       - Terrain + map loading: specs/terrain-map-loading.md

parity/README.md

@@ -0,0 +1,20 @@
+# Render Parity Dataset
+
+This folder stores parity-test input for `crates/render-parity`.
+
+- `cases.toml`: list of deterministic render cases.
+- `reference/*.png`: baseline frames captured from the original renderer.
+
+Expected workflow:
+
+1. Capture baseline PNG frames from original game/editor for each case.
+2. Add entries to `cases.toml`.
+3. Run:
+
+```bash
+cargo run -p render-parity -- \
+  --manifest parity/cases.toml \
+  --output-dir target/render-parity/current
+```
+
+On failure, diff images are saved to `target/render-parity/current/diff`.

parity/cases.toml

@@ -0,0 +1,27 @@
+[meta]
+# Global defaults for all cases.
+width = 1280
+height = 720
+lod = 0
+group = 0
+angle = 0.0
+
+# Per-pixel change threshold for the "changed pixel ratio" metric.
+diff_threshold = 8
+
+# Allowed thresholds (case fails if any limit is exceeded).
+max_mean_abs = 2.0
+max_changed_ratio = 0.010
+
+# Add one block per model.
+#
+# [[case]]
+# id = "animals_a_l_01"
+# archive = "../testdata/Parkan - Iron Strategy/animals.rlb"
+# model = "A_L_01.msh"
+# reference = "reference/animals_a_l_01.png"
+# lod = 0
+# group = 0
+# angle = 0.0
+# max_mean_abs = 2.0
+# max_changed_ratio = 0.010