1 files changed, 73 insertions, 0 deletions
diff --git a/weathereffects/assets/shaders/utils.agsl b/weathereffects/assets/shaders/utils.agsl
new file mode 100644
index 0000000..ffc651a
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+++ b/weathereffects/assets/shaders/utils.agsl
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+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+highp float idGenerator(vec2 point) {
+    vec2 p = fract(point * vec2(723.123, 236.209));
+    p += dot(p, p + 17.1512);
+    return fract(p.x * p.y);
+}
+
+highp float idGenerator(float value) {
+    return idGenerator(vec2(value, 1.412));
+}
+
+mat2 rotationMat(float angleRad) {
+  float c=cos(angleRad);
+  float s=sin(angleRad);
+  // |  c  -s  |
+  // |  s   c  |
+  return mat2(
+    c, s, // First column.
+    -s, c // second column.
+  );
+}
+
+vec2 rotateAroundPoint(vec2 point, vec2 centerPoint, float angleRad) {
+    return (point - centerPoint) * rotationMat(angleRad) + centerPoint;
+}
+
+// function created on Grapher (equation decided by testing in Grapher).
+float wiggle(float time, float wiggleSpeed) {
+    return sin(wiggleSpeed * time + 0.5 * sin(wiggleSpeed * 5. * time))
+        * sin(wiggleSpeed * time) - 0.5;
+}
+
+// Noise range of [-1.0, 1.0[ with triangle distribution.
+float triangleNoise(vec2 n) {
+    n  = fract(n * vec2(5.3987, 5.4421));
+    n += dot(n.yx, n.xy + vec2(21.5351, 14.3137));
+    float xy = n.x * n.y;
+    // compute in [0..2[ and remap to [-1.0..1.0[
+    return fract(xy * 95.4307) + fract(xy * 75.04961) - 1.0;
+}
+
+/*
+ * This is the normal blend mode in which the foreground is painted on top of the background based
+ * on the foreground opacity.
+ *
+ * @param b the background color.
+ * @param f the foreground color.
+ * @param o the mask or the foreground alpha.
+ *
+ * Note: this blending function expects the foreground to have premultiplied alpha.
+ */
+vec3 normalBlend(vec3 b, vec3 f, float o) {
+    return b * (1. - o) + f;
+}
+
+vec3 normalBlendWithWhiteSrc(vec3 b, float o) {
+    return b * (1. - o) + o;
+}