Anton's Research Ramblings

Dissolve Effect

I made a simple dissolve effect in WebGL. The source code is demo number 042 at https://github.com/capnramses/opengl_expmts. You can also view the source of this page. The idea was to replicate something like the dematerialisation shader effect you see in video games as a way of removing 3D models of dead monsters. A similar effect is used to fade-in and fade-out objects in the distance. I originally considered using an arrangement of sine waves written into the fragment shader, but ended up using a cloud map that I generated in GIMP automatically:

The idea for animation is that you have a timer that you express, in the shader, as a sliding value between 0.0 and 1.0. I used the regular texture coordinates for the mesh, and sampled the clouds texture behind the scenes, as a second texture in the fragment shader, such that it could replace the checkerboard if I wanted. Every time the mesh is drawn, each fragment shader invocation compares the sample it gets from the heightmap - a value between 0.0 and 1.0 - with the value from the timer. Any fragments with a difference in values of less than 0.01 are discarded, which creates the holes. I added some burning colour around the holes by modifying the colour of fragments in the range of 0.1 to 0.01.

If you like this sort of thing - Mozilla has great WebGL tutorials. You might also check out my OpenGL tutorials/intro, which are aimed at students.

Anton Gerdelan. Dublin, Ireland.