Add trail to bloom

shader/fullscreen/alphaHalve.frag

@@ -0,0 +1,3 @@
+#version 430 core
+out vec4 fColor;
+void main () { fColor = vec4(0,0,0,0.5);}

shader/fullscreen/alphaHalve.vert

@@ -0,0 +1,4 @@
+#version 430 core
+layout (location = 0) in vec2 position;
+void main()
+{ gl_Position = vec4 (position, 0 , 1);}

shader/texture/bloomBlur.frag

@@ -46,7 +46,7 @@ void main()
     float alph = 0.0;
     for (int i = 0; i < 9; i++)
         alph += sampleTex[i].a;
-    alph = sampleTex[5].a + alph/9.0;
+    alph = max(sampleTex[4].a, alph/9.0);
         //
     //fColor = col;
     fColor = vec4(col.rgb/col.a,alph);

src/Data/Preload/Render.hs

@@ -16,6 +16,7 @@ data RenderData = RenderData
     , _textureShader            :: FullShader
     , _textureArrayShader       :: FullShader
     , _fullscreenShader         :: FullShader
+    , _fullscreenAlphaHalveShader         :: FullShader
     , _boxBlurShader            :: FullShader
     , _grayscaleShader          :: FullShader
     , _pictureShaders           :: [FullShader]

src/Dodge/Render.hs

@@ -84,12 +84,18 @@ doDrawing pdata w = do
     depthFunc $= Just Always
     --blend $= Disabled
     textureBinding Texture2D $= Just (snd $ _fboBloom pdata)
-    clear [ColorBuffer]
+    --clear [ColorBuffer]
     --blendFunc $= (SrcAlpha,OneMinusSrcAlpha)
+    blendFuncSeparate $= ((Zero,One), (Zero,SrcAlpha))
+    bindShaderBuffers [_fullscreenAlphaHalveShader pdata] [4]
+    drawShader (_fullscreenAlphaHalveShader pdata) 4
     blendFunc $= (One,Zero)
     bindShaderBuffers [_boxBlurShader pdata] [4]
+    blendFunc $= (SrcAlpha,OneMinusSrcAlpha)
     drawShader (_boxBlurShader pdata) 4
+    blendFunc $= (One,Zero)
     pingPongBlur pdata
+    replicateM_ 5 $ pingPongBlur pdata
     --blend $= Enabled
 
     blendFunc $= (SrcAlpha,OneMinusSrcAlpha)

src/Preload/Render.hs

@@ -47,6 +47,10 @@ preloadRender = do
     cslist <- makeShader "twoD/character" [vert,frag] [3,4,2] ETriangles pokeCharStrat
                   >>= addTexture "data/texture/charMap.png"
     basicTweakZShad <- makeShader "twoD/basicTweakZ" [vert,frag] [4,4] ETriangles pokeTriTweakZ
+-- fullscreen shaders
+    fullscreenAlphaHalveShad <- makeShader "fullscreen/alphaHalve" [vert,frag] [2] ETriangleStrip $
+        const cornerListNoCoord
+    pokeArray (_vboPointer $ _vaoVBO $ _shaderVAO fullscreenAlphaHalveShad) $ concat cornerListNoCoord
 -- texture shaders, no textures attached
     fsShad <- makeShader "texture/simple" [vert,frag] [2,2] ETriangleStrip $ const cornerList
     -- note we directly poke the shader vertex data here
@@ -103,6 +107,7 @@ preloadRender = do
         , _textureShader            = textShad
         , _textureArrayShader       = textArrayShad
         , _fullscreenShader         = fsShad
+        , _fullscreenAlphaHalveShader = fullscreenAlphaHalveShad
         , _boxBlurShader            = boxBlurShad
         , _grayscaleShader          = grayscaleShad
         , _spareFBO                 = fbo
@@ -125,6 +130,13 @@ cornerList =
         ,[-1,-1,0,0]
         ,[ 1,-1,1,0]
         ]
+cornerListNoCoord :: [[Float]]
+cornerListNoCoord =
+        [[-1, 1]
+        ,[ 1, 1]
+        ,[-1,-1]
+        ,[ 1,-1]
+        ]
 --------------------end preloadRender
 
 setupFramebufferWithStencil :: IO (FramebufferObject, TextureObject,RenderbufferObject)