4 replies to this topic

[gz0]

Probably a newbie question/error, but please bear with me.
I have a VBO with mesh data. I'm trying to displace the vertexes, based on a float texture with the vertex shader.

The displacement shader works in immediate mode, 100%. But somehow when I apply the shader on the VBO things go wrong. It looks like the shader can't read the texel values from the texture when using VBO.

dv0 = texture2D(hData, gl_MultiTexCoord0.st);

When displacing with dv0.x (height values are stored in "red"), it is like it reads the value 0, cuz no vertex changes position. If I just displace the vertex, with texture coordinates multiplied with a scaling factor(just to check that the displacement indeed works). I get a nice inclined plane, as expected.

The fragment shader however, reads the value of the texel just fine.

Format of the height texture.

glGenTextures(1, &m_HeightTex);

glBindTexture(GL_TEXTURE_2D, m_HeightTex);

glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_NEAREST);

glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_NEAREST);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);

glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);

glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA_FLOAT32_ATI, 256,256,0,GL_RGBA,GL_FLOAT, tex);

I just wonder if it's anything special with VBO, some state or something I have ignored.

[Sol_HSA]

gz0 said:

Probably a newbie question/error, but please bear with me.
I have a VBO with mesh data. I'm trying to displace the vertexes, based on a float texture with the vertex shader.

Most likely your card does not support texture fetches from vertex shaders (pretty much none do currently). Thus the vertex shader is run on the CPU, which then can't access the VBO for some reason..

[gz0]

ty, will do it another way then =)

[martinsm]

Nvidia 6x, 7x and 8x videocards supports texture fetches in vertex shader in OpenGL.
ATI doesn't (in OpenGL).

[gz0]

Not via texture2D call though, you must use texture2DLod, someone could have told me that :P