[orx-noise] Bring back GLSL NoiseFilters.kt (#277)

orx-noise/src/shaders/glsl/noise/cell.frag

@@ -0,0 +1,54 @@
+// uniforms
+uniform vec4 gain;
+uniform vec4 bias;
+uniform vec2 seed;
+
+uniform vec2 scale;
+uniform vec2 lacunarity;
+uniform vec4 decay;
+uniform int octaves;
+uniform bool premultipliedAlpha;
+
+// varyings
+in vec2 v_texCoord0;
+
+// outputs
+out vec4 o_output;
+
+vec2 hash22(vec2 p) {
+    float n = sin(dot(p, vec2(41, 289)));
+    return fract(vec2(262144, 32768)*n);
+}
+
+float cell(vec2 p) {
+    vec2 ip = floor(p);
+    p = fract(p);
+
+    float d = 1.0;
+    for (int i = -1; i <= 1; i++) {
+        for (int j = -1; j <= 1; j++) {
+            vec2 cellRef = vec2(i, j);
+            vec2 offset = hash22(ip + cellRef);
+            vec2 r = cellRef + offset - p;
+            float d2 = dot(r, r);
+            d = min(d, d2);
+        }
+    }
+    return d;
+}
+
+void main() {
+    vec4 result = vec4(0.0);
+    vec4 _gain = gain;
+    vec2 _scale = scale;
+    for (int o = 0; o < octaves; ++o) {
+        result += cell((v_texCoord0+seed) * _scale) * _gain;
+        _scale *= lacunarity;
+        _gain *= decay;
+    }
+    o_output = result + bias;
+
+    if (premultipliedAlpha) {
+        o_output.rgb *= o_output.a;
+    }
+}