Minimesh Shader

[serial]

Would it be possible to use a texture image source for positioning minimeshes instead of an array?  I'm getting better at the pixel shaders but the vertex shaders are still beyond me at this point. 

I thought I read some where you can use a texture sampler in a vertex shader but I can't find it again.

[newborn]

this has nothing to do with shaders (unless I did not understand your question properly)



texture.lock(iTexture)
for x = 0 to iTextureWidth step fPrecision
  for y = 0 to iTextureHeight step fPrecision
    if texture.getpixel(x, y) = white then
      iMinimesh += 1
      minimesh.setposition(iMinimesh, x, landscape.getheight(x, y), y)
    end if
  next
next
texture.unlock(iTexture)


fprecision is the distance between your minimesh

[serial]

Sort of,  I want to be able to do that inside of a shader though.

[Zaknafein]

Vertex texture sampling is only available with vs_3_0 and more, so pretty recent cards. If you're planning a public release, it's not a very viable solution.
But yes, it's possible and can be used for moving instances around. It's the same functions as you'd use in a vertex shader (tex2D) but instead of using it as a colour, you can use it as a modifier to the position of your current vertex. If all vertices inside an instance share the same modifier, then the whole instance has moved.

[Waterman]

Is there something that uniquely identifies an instance of the minimesh when it's drawn? (For  and in the vs)

I'd be interested in hearnig the technique for this...

[JukkaKevät]

Check out the Million Particle System, it handles particle systems entirely in GPU.

http://www.2ld.de/gdc2004/

edit:
Also something which can be useful...
http://developer.nvidia.com/object/using_vertex_textures.html