🚚 Move shader code to GLSL files

resources/shaders/broken-glass.glsl

@@ -0,0 +1,49 @@
+cogl_color_out = vec4(0, 0, 0, 0);
+
+float progress = uForOpening ? 1.0 - uProgress : uProgress;
+
+// Draw the individual shard layers.
+for (float i = 0; i < SHARD_LAYERS; ++i) {
+
+  // To enable drawing shards outside of the window bounds, the actor was scaled
+  // by ACTOR_SCALE. Here we scale and move the texture coordinates so that the
+  // window gets drawn at the correct position again.
+  vec2 coords = cogl_tex_coord_in[0].st * ACTOR_SCALE - PADDING;
+
+  // Scale and rotate around our epicenter.
+  coords -= uEpicenter;
+
+  // Scale each layer a bit differently.
+  coords /= mix(1.0, 1.0 + uBlowForce * (i + 2) / SHARD_LAYERS, progress);
+
+  // Rotate each layer a bit differently.
+  float rotation = (mod(i, 2.0) - 0.5) * 0.2 * progress;
+  coords         = vec2(coords.x * cos(rotation) - coords.y * sin(rotation),
+                coords.x * sin(rotation) + coords.y * cos(rotation));
+
+  // Move down each layer a bit.
+  float gravity =
+    (uForOpening ? -1.0 : 1.0) * uGravity * 0.1 * (i + 1) * progress * progress;
+  coords += vec2(0, gravity);
+
+  // Restore correct position.
+  coords += uEpicenter;
+
+  // Retrieve information from the shard texture for our layer.
+  vec2 shardCoords = (coords + uSeed) * uSize / uShardScale / 500.0;
+  vec2 shardMap    = texture2D(uShardTexture, shardCoords).rg;
+
+  // The green channel contains a random value in [0..1] for each shard. We
+  // discretize this into SHARD_LAYERS bins and check if our layer falls into
+  // the bin of the current shard.
+  float shardGroup = floor(shardMap.g * SHARD_LAYERS * 0.999);
+
+  if (shardGroup == i && (shardMap.x - pow(progress + 0.1, 2)) > 0) {
+    cogl_color_out = texture2D(uTexture, coords);
+  }
+}
+
+// Shell.GLSLEffect uses straight alpha. So we have to convert from premultiplied.
+if (cogl_color_out.a > 0) {
+  cogl_color_out.rgb /= cogl_color_out.a;
+}