ps3: port our naive dithering algorithm to the PS3's shader language.

src/scene.cpp

@@ -180,7 +180,7 @@ void Scene::Render() // XXX: rename to Blit()
 #endif
 #if 0
             "    float mul = 2.0;\n"
-#if 0
+#if 1
             "    vec2 d1 = mod(vec2(gl_FragCoord), vec2(2.0, 2.0));\n"
             "    float t1 = mod(3.0 * d1.x + 2.0 * d1.y, 4.0);\n"
             "    float dx2 = mod(floor(gl_FragCoord.x * 0.5), 2.0);\n"
@@ -189,9 +189,9 @@ void Scene::Render() // XXX: rename to Blit()
             "    float dx3 = mod(floor(gl_FragCoord.x * 0.25), 2.0);\n"
             "    float dy3 = mod(floor(gl_FragCoord.y * 0.25), 2.0);\n"
             "    float t3 = mod(3.0 * dx3 + 2.0 * dy3, 4.0);\n"
-            "    float t1 = (1.0 + 16.0 * t1 + 4.0 * t2 + t3) / 65.0;\n"
-            "    float t2 = t1;\n"
-            "    float t3 = t1;\n"
+            "    t1 = (1.0 + 16.0 * t1 + 4.0 * t2 + t3) / 65.0;\n"
+            "    t2 = t1;\n"
+            "    t3 = t1;\n"
 #else
             "    float rand = sin(gl_FragCoord.x * 1.23456) * 123.456\n"
             "               + cos(gl_FragCoord.y * 2.34567) * 789.012;\n"
@@ -226,10 +226,45 @@ void Scene::Render() // XXX: rename to Blit()
             "}",
 
             "void main(float2 in_TexCoord : TEXCOORD0,"
+            "          float4 in_FragCoord : WPOS,"
             "          uniform sampler2D tex,"
             "          out float4 out_FragColor : COLOR)"
             "{"
-            "    out_FragColor = tex2D(tex, in_TexCoord);"
+            "    float4 col = tex2D(tex, in_TexCoord);"
+#if 0
+            "    float mul = 2.0;\n"
+            "    float t1, t2, t3;\n"
+#if 1
+            "    float dx1 = frac(in_FragCoord.x * 0.5) * 2.0;\n"
+            "    float dy1 = frac(in_FragCoord.y * 0.5) * 2.0;\n"
+            "    t1 = frac((3.0 * dx1 + 2.0 * dy1) / 4.0) * 4.0;\n"
+            "    float dx2 = frac(floor(in_FragCoord.x * 0.5) * 0.5) * 2.0;\n"
+            "    float dy2 = frac(floor(in_FragCoord.y * 0.5) * 0.5) * 2.0;\n"
+            "    t2 = frac((3.0 * dx2 + 2.0 * dy2) / 4.0) * 4.0;\n"
+            "    float dx3 = frac(floor(in_FragCoord.x * 0.25) * 0.5) * 2.0;\n"
+            "    float dy3 = frac(floor(in_FragCoord.y * 0.25) * 0.5) * 2.0;\n"
+            "    t3 = frac((3.0 * dx3 + 2.0 * dy3) / 4.0) * 4.0;\n"
+            "    t1 = (1.0 + 4.0 * t1 + t2) / 17.0;\n"
+            "    t2 = t1;\n"
+            "    t3 = t1;\n"
+#else
+            "    float rand = sin(in_FragCoord.x * 1.23456) * 123.456\n"
+            "               + cos(in_FragCoord.y * 2.34567) * 789.012;\n"
+            "    t1 = frac(sin(rand) * 17.13043);\n"
+            "    t2 = frac(sin(rand) * 27.13043);\n"
+            "    t3 = frac(sin(rand) * 37.13043);\n"
+#endif
+            "    float fracx = frac(col.x * mul);\n"
+            "    float fracy = frac(col.y * mul);\n"
+            "    float fracz = frac(col.z * mul);\n"
+            "    fracx = fracx > t1 ? 1.0 : 0.0;\n"
+            "    fracy = fracy > t2 ? 1.0 : 0.0;\n"
+            "    fracz = fracz > t3 ? 1.0 : 0.0;\n"
+            "    col.x = (floor(col.x * mul) + fracx) / mul;\n"
+            "    col.y = (floor(col.y * mul) + fracy) / mul;\n"
+            "    col.z = (floor(col.z * mul) + fracz) / mul;\n"
+#endif
+            "    out_FragColor = col;"
             "}");
 #endif
     }