wb oit : fix final target alpha

Author: ManifoldFR

shaders/compiled/WBOITComposite.frag.msl

@@ -74,7 +74,7 @@ struct KernelContext_0
     }
 
 #line 13
-    pixelOutput_0 _S7 = { float4(color_0, _S4) };
+    pixelOutput_0 _S7 = { float4(color_0, 1.0 - _S4) };
 
 
 

shaders/compiled/WBOITComposite.frag.spv

@@ -14,5 +14,5 @@ float4 main(float4 fragCoord : SV_Position,
         color = accum.rgb / accum.a;
     }
 
-    return float4(color, reveal);
+    return float4(color, 1.0 - reveal);
 }

shaders/src/WBOITComposite.frag.slang

@@ -271,10 +271,10 @@ void RobotScene::initCompositePipeline(const MeshLayout &layout) {
   color_target.format = m_renderer.getSwapchainTextureFormat();
   color_target.blend_state = {
       .src_color_blendfactor = SDL_GPU_BLENDFACTOR_ONE,
-      .dst_color_blendfactor = SDL_GPU_BLENDFACTOR_SRC_ALPHA,
+      .dst_color_blendfactor = SDL_GPU_BLENDFACTOR_ONE_MINUS_SRC_ALPHA,
       .color_blend_op = SDL_GPU_BLENDOP_ADD,
-      .src_alpha_blendfactor = SDL_GPU_BLENDFACTOR_ZERO,
-      .dst_alpha_blendfactor = SDL_GPU_BLENDFACTOR_ONE,
+      .src_alpha_blendfactor = SDL_GPU_BLENDFACTOR_ONE,
+      .dst_alpha_blendfactor = SDL_GPU_BLENDFACTOR_ONE_MINUS_SRC_ALPHA,
       .alpha_blend_op = SDL_GPU_BLENDOP_ADD,
       .enable_blend = true,
   };