fix: preserve native sky sprite screen depth

adapters/fparkan-render-vulkan/src/ffi/smoke.rs

@@ -3,7 +3,7 @@
 use ash::vk;
 use fparkan_render::{LegacyDepthMode, LegacyPipelineState};
 
-use super::smoke_types::resolve_draw_texture_indices;
+use super::smoke_types::{resolve_draw_texture_indices, VulkanStaticMaterial};
 use super::update_material_texture_descriptor;
 use super::{
     create_command_pool, create_frame_sync, create_index_buffer, create_static_mesh_index_buffer,
@@ -361,18 +361,7 @@ impl VulkanSmokeRenderer {
             create_info
                 .materials
                 .iter()
-                .map(|material| {
-                    let combiner_mode = if material.lightmap_mode {
-                        3.0
-                    } else if material.sky_nebula_stars {
-                        2.0
-                    } else if material.unlit {
-                        1.0
-                    } else {
-                        0.0
-                    };
-                    combiner_mode + if material.sky_far_depth { 4.0 } else { 0.0 }
-                })
+                .map(VulkanStaticMaterial::encoded_material_mode)
                 .collect()
         };
         let material_specular = if create_info.materials.is_empty() {

adapters/fparkan-render-vulkan/src/ffi/smoke_types.rs

@@ -505,6 +505,33 @@ pub struct VulkanStaticMaterial {
     /// renderer projection choice; it is not a claim about the original D3D
     /// depth-bit encoding.
     pub sky_far_depth: bool,
+    /// Push material mode bit 8 and treat positions as Vulkan clip-space
+    /// `XYZRHW` vertices. Their x/y coordinates are converted from viewport
+    /// pixels by the caller and z retains the native `0.999` depth.
+    pub screen_tl: bool,
+}
+
+impl VulkanStaticMaterial {
+    pub(crate) fn encoded_material_mode(&self) -> f32 {
+        let combiner_mode = if self.screen_tl {
+            1.0
+        } else if self.lightmap_mode {
+            3.0
+        } else if self.sky_nebula_stars {
+            2.0
+        } else if self.unlit {
+            1.0
+        } else {
+            0.0
+        };
+        combiner_mode
+            + if self.sky_far_depth && !self.screen_tl {
+                4.0
+            } else {
+                0.0
+            }
+            + if self.screen_tl { 8.0 } else { 0.0 }
+    }
 }
 
 /// One authored RGBA8 mip level accepted by the Vulkan texture upload path.
@@ -1028,6 +1055,7 @@ mod static_mesh_tests {
                 sky_nebula_stars: false,
                 lightmap_mode: false,
                 sky_far_depth: false,
+                screen_tl: false,
             },
             VulkanStaticMaterial {
                 material_index: 7,
@@ -1054,9 +1082,19 @@ mod static_mesh_tests {
                 sky_nebula_stars: false,
                 lightmap_mode: false,
                 sky_far_depth: false,
+                screen_tl: false,
             },
         ];
 
+        let mut screen_tl = materials[0].clone();
+        screen_tl.screen_tl = true;
+        screen_tl.sky_far_depth = true;
+        assert_eq!(screen_tl.encoded_material_mode(), 9.0);
+        let mut far_sky = materials[0].clone();
+        far_sky.unlit = true;
+        far_sky.sky_far_depth = true;
+        assert_eq!(far_sky.encoded_material_mode(), 5.0);
+
         assert_eq!(
             resolve_draw_texture_indices(&ranges, &materials),
             Ok(vec![1, 0])

adapters/fparkan-render-vulkan/src/ffi/tests.rs

@@ -533,7 +533,7 @@ fn native_specular_reference_uses_squared_power_and_total_overflow_curve() {
 fn shader_computes_radial_fog_per_vertex_and_interpolates_it() {
     let vertex = include_str!("../../shaders/triangle.vert");
     let fragment = include_str!("../../shaders/triangle.frag");
-    assert!(vertex.contains("out_fog_factor = native_fog_factor(in_position);"));
+    assert!(vertex.contains("out_fog_factor = screen_tl ? 0.0 : native_fog_factor(in_position);"));
     assert!(fragment.contains("layout(location = 4) in float in_fog_factor;"));
     assert!(!fragment.contains("distance(in_world_position"));
     assert!(!fragment.contains("float fog_factor()"));