[orx-fx] convert to MPP

orx-fx/src/shaders/glsl/distort/stack-repeat.frag

@@ -0,0 +1,40 @@
+in vec2 v_texCoord0;
+uniform sampler2D tex0;// input
+uniform int repeats;
+uniform float zoom;
+uniform float xOrigin;
+uniform float yOrigin;
+uniform float xOffset;
+uniform float yOffset;
+uniform float rotation;
+
+out vec4 o_color;
+void main() {
+    vec2 origin = vec2((xOrigin+1.0)/2.0, (yOrigin+1.0)/2.0);
+    vec2 ts = textureSize(tex0, 0);
+    float r = ts.x/ts.y;
+    vec2 offset = vec2(1.0, r) * vec2(xOffset, yOffset);
+    vec2 uv = v_texCoord0 - vec2(origin);
+    float rad = (rotation/180) * 3.1415926535;
+    vec2 cs0 = vec2(cos(rad), -sin(rad));
+    vec2 cs1 = vec2(sin(rad), cos(rad));
+    mat2 rotStep = mat2(cs0, cs1);
+
+    mat2 rot = rotStep;
+    vec4 c = texture(tex0, v_texCoord0);
+    for (int i = 1; i <= repeats; ++i) {
+        //vec2 s = (uv * (1.0 + zoom) * i) + vec2(0.5);
+        vec2 s = (rot * uv * pow(1.0 + zoom,i*1.0) )+ vec2(origin) + vec2(offset) * i;
+        float f = s.x >= 0.0 && s.y > 0.0 && s.x < 1.0 && s.y < 1.0? 1.0 : 0.0;
+        vec4 sc = texture(tex0, s) * f;
+
+        c = c * (1.0-sc.a) + sc;
+        if (c.a > 1.0) {
+            c.a = 1.0;
+        }
+        rot *= rotStep;
+    }
+
+
+    o_color = c;
+}