material initial and pose fix

NResUI/Rendering/Viewport/ViewportMaterial.cs

@@ -0,0 +1,16 @@
+namespace NResUI.Rendering.Viewport;
+
+public sealed class ViewportMaterial
+{
+    public string Name { get; }
+    public uint TextureHandle { get; }
+    public bool HasTexture => TextureHandle != 0;
+
+    public ViewportMaterial(string name, uint textureHandle = 0)
+    {
+        Name = name;
+        TextureHandle = textureHandle;
+    }
+
+    public static ViewportMaterial Untextured { get; } = new("Untextured");
+}