Million mesh programmatically?

Question

I have a flat surface drawn with a single fullscreen GL_QUAD.

I want to deform this surface at each point specified by my GL_Texture2D, preferably through some kind of shader.

In my mind, black could correspond to flat and white could correspond to a hill.

I want to have about 4 million points on my terrain and update them at each step in my program.

How would I use a geometry shader to do this? Is a shader able to generate new veritices?

Can you restructure your question so that it's not answerable with a simple "yes" or "no"? — Robert Harvey, Aug 13 '13 at 19:36
I don't see how this is related to any programming language other than GLSL; remove the c++ tag. — DanielKO, Aug 13 '13 at 20:56
Are you using OpenGL 4.0 or higher? If you are, then it sounds like you should be using tessellation shaders (not a geometry shader) to do what you want. — GuyRT, Aug 14 '13 at 10:53
I don't see why you would need a geometry shader. Just use a vertex shader as @jozxyqk suggested. If you really want to modify the vertex coordinates at each step, i.e. save the calculations done in the vertex shader, have a look at transform feedback. — Gigo, Aug 16 '13 at 02:47

score 2 · Answer 1 · answered Aug 15 '13 at 15:24

The simplest way would be to generate a large triangle strip grid, upload it to a VBO and draw it, using the vertex shader to alter just the up coordinate. The vertex shader can also generate normals from the heightmap (or supply a normal map), which then get passed to the fragment shader for lighting.

To avoid storing a huge amount of data for the vertices, use glVertexID to generate the vertex positions from scratch in the vertex shader. Don't bind any buffers, simply call glDrawArrays(GL_TRIANGLE_STRIP, 0, lots).

As GuyRT mentioned, a tessellation shader would be good too and allow you to vary the tessellation detail based on the camera's distance to the mesh. This would be more work though.

Million mesh programmatically?

1 Answers1