Allow tweaking z buffer when rendering polygon, improve explosion render

src/Preload/Render.hs

@@ -45,6 +45,7 @@ preloadRender = do
     bezierQuadShader <- makeShader "twoD/bezierQuad" [vert,frag] [3,4,4]  ETriangleStrip pokeBezQStrat
     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
 -- 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
@@ -75,7 +76,8 @@ preloadRender = do
     clearColor $= Color4 0 0 0 1
 
     return $ RenderData
-        { _pictureShaders           = [bslist,lslist,cslist,aslist,eslist,bezierQuadShader]
+        { _pictureShaders           = 
+            [bslist,lslist,cslist,aslist,eslist,bezierQuadShader,basicTweakZShad]
         , _lightingSurfaceShader    = lightingSurfaceShad
         , _lightingLineShadowShader = lightingLineShadowShad
         , _lightingOccludeShader    = wsShad
@@ -160,6 +162,11 @@ pokeBezQStrat (RenderBezQ vs) = fmap (\((x,y,z),(r,g,b,a),(s,t,u,v)) -> [x,y,z,r
                                      vs
 pokeBezQStrat _ = []
 
+
+pokeTriTweakZ :: RenderType -> [[Float]]
+pokeTriTweakZ (RenderPolyZ vs) = fmap (\(p,co,z) -> flat3 p ++ [z] ++ flat4 co) vs
+pokeTriTweakZ _ = []
+
 {-# INLINE pokeTriStrat #-}
 pokeTriStrat,pokeCharStrat,pokeArcStrat,pokeLineStrat,pokeEllStrat :: RenderType -> [[Float]]
 pokeTriStrat (RenderPoly vs) = fmap (\(p,co) -> flat3 p ++ flat4 co) vs