[client] egl: add ffx_cas post process filter

client/renderers/EGL/shader/ffx_cas.frag

@@ -0,0 +1,68 @@
+#version 300 es
+
+precision mediump float;
+
+in  vec2  iFragCoord;
+out vec4  fragColor;
+
+uniform sampler2D iChannel0;
+uniform uvec2     uInRes[8];
+uniform uvec2     uOutRes;
+
+// the following are not available until verion 400 or later
+// so we implement our own versions of them
+uint bitfieldExtract(uint val, int off, int size)
+{
+  uint mask = uint((1 << size) - 1);
+  return uint(val >> off) & mask;
+}
+
+uint bitfieldInsert(uint a, uint b, int c, int d)
+{
+  uint mask = ~(0xffffffffu << d) << c;
+  mask = ~mask;
+  a &= mask;
+  return a | (b << c);
+}
+
+#define A_GPU 1
+#define A_GLSL 1
+
+#include "ffx_a.h"
+
+vec3 imageLoad(ivec2 point)
+{
+  return texelFetch(iChannel0, point, 0).rgb;
+}
+
+AF3 CasLoad(ASU2 p)
+{
+  return imageLoad(p).rgb;
+}
+
+void CasInput(inout AF1 r,inout AF1 g,inout AF1 b) {}
+
+#include "ffx_cas.h"
+
+void main()
+{
+  uvec2 point = uvec2(iFragCoord * vec2(uInRes[0].xy));
+   
+  vec4 color;
+  vec2 inputResolution  = vec2(uInRes[0]);
+  vec2 outputResolution = vec2(uOutRes);
+  float sharpnessTuning = 1.0f;
+
+  uvec4 const0;
+  uvec4 const1;
+
+  CasSetup(const0, const1, sharpnessTuning,
+    inputResolution.x, inputResolution.y, 
+    outputResolution.x, outputResolution.y);
+
+  CasFilter(
+    fragColor.r, fragColor.g, fragColor.b,
+    point,
+    const0, const1,
+    true);
+}