experimental map shaders

modules/game_shaders/shaders/grayscale.frag

@@ -0,0 +1,14 @@
+uniform float u_Time;
+uniform sampler2D u_Tex0;
+varying vec2 v_TexCoord;
+
+vec4 grayscale(vec4 color)
+{
+    float gray = dot(color.rgb, vec3(0.299, 0.587, 0.114));
+    return vec4(gray, gray, gray, 1);
+}
+
+void main()
+{
+    gl_FragColor = grayscale(texture2D(u_Tex0, v_TexCoord));
+}