As a part of ongoing polish work I wanted to animate bugs' death somehow. Here's how it looked like recently:
1. A dying insect breaks down into a few parts.
2. There's a simple particle effect on top.
3. A stain is created underneath. It is animated, so it "spills" from the insect.
4. The dead parts attract other small insects, which feed on such carcasses.
The 4th part needs a little bit more work, but I'm quite satisfied how it all turned out.
The stain below a dying insect is barely visible, but I had a lot of fun putting it together.
1. A stain is actually a triangle fan. I start with a fan of 30 triangles and radius=1. The positioning and scaling are done in the vertex shader. Scale is animated, so the fan appears small and then grows a little (I colored triangles with different shades of grey, hope they're noticeable).
Note that there is no jagged edge between the first and last triangle (black and white ones). That's why I generated a tileable noise texture.
3. Then I just added a texture in the fragment shader and voilà!