bayer alpha for particles

src/shaders/bayeralpha.frag

@@ -0,0 +1,28 @@
+#ifdef GL_ES
+precision mediump float;
+#endif
+
+in vec4 v_color;
+in vec2 v_texCoords;
+
+uniform sampler2D u_texture; // world texture, has alpha value that is meaningful
+uniform float acount = 2.0;
+
+out vec4 fragColor;
+
+const int bayer[4 * 4] = int[](0,8,2,10,12,4,14,6,3,11,1,9,15,7,13,5);
+const float bayerSize = 4.0;
+const float bayerDivider = bayerSize * bayerSize;
+
+float nearestAlpha(float alpha) {
+    return min(1.0, floor(alpha + 0.5));
+}
+
+void main() {
+    vec4 inColor = texture(u_texture, v_texCoords) * v_color;
+    vec2 entry = mod(gl_FragCoord.xy, vec2(bayerSize, bayerSize));
+
+    float alpha = nearestAlpha((inColor.a * 16.0 / 15.0) + (bayer[int(entry.y) * int(bayerSize) + int(entry.x)] / bayerDivider - 0.5));
+
+    fragColor = vec4(inColor.rgb, alpha);
+}