🚚 Move shader code to GLSL files

resources/shaders/trex.glsl

@@ -0,0 +1,51 @@
+float progress = uForOpening ? 1.0 - uProgress : uProgress;
+
+// Warp the texture coordinates to create a blow-up effect.
+vec2 coords = cogl_tex_coord_in[0].st * 2.0 - 1.0;
+float dist  = length(coords);
+coords      = (coords / dist * pow(dist, 1.0 + uWarpIntensity)) * 0.5 + 0.5;
+coords      = mix(cogl_tex_coord_in[0].st, coords, progress);
+
+// Accumulate several random scratches. The color in the scratch map refers to the
+// relative time when the respective part will become invisible. Therefore we can
+// add a value to make the scratch appear later.
+float scratchMap = 1.0;
+for (int i = 0; i < uNumClaws; ++i) {
+  vec2 uv     = getClawUV(coords, 1.0 / uClawSize, uSeed * (i + 1));
+  float delay = i / uNumClaws * MAX_SPAWN_TIME;
+  scratchMap  = min(scratchMap, clamp(texture2D(uClawTexture, uv).r + delay, 0, 1));
+}
+
+// Get the window texture. We shift the texture lookup by the local derivative of
+// the claw texture in order to mimic some folding distortion.
+vec2 offset    = vec2(dFdx(scratchMap), dFdy(scratchMap)) * progress * 0.5;
+cogl_color_out = texture2D(uTexture, coords + offset);
+
+// 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;
+}
+
+// Add colorful flashes.
+float flashIntensity = 1.0 / FLASH_INTENSITY * (scratchMap - progress) + 1;
+if (flashIntensity < 0 || flashIntensity >= 1) {
+  flashIntensity = 0;
+}
+
+// Hide flashes where there is now window.
+vec4 flash = uFlashColor;
+flash.a *= flashIntensity * cogl_color_out.a * (1.0 - progress);
+
+// Hide scratched out parts.
+cogl_color_out.a *= (scratchMap > progress ? 1 : 0);
+
+// Add flash color.
+cogl_color_out = alphaOver(cogl_color_out, flash);
+
+// Fade out the remaining shards.
+float fadeProgress = smoothstep(0, 1, (progress - 1.0 + FF_TIME) / FF_TIME);
+cogl_color_out.a *= sqrt(1 - fadeProgress * fadeProgress);
+
+// These are pretty useful for understanding how this works.
+// cogl_color_out = vec4(vec3(flashIntensity), 1);
+// cogl_color_out = vec4(vec3(scratchMap), 1);