Hi Jordi, I think the problem is in this line of code in your vertex shader:
vec4 pos= gl_Vertex+ vec4(texture1D(texturePos,(float(gl_InstanceID)/nInstances)).xyz,0.);
I think that texels are placed in the [0..1] range using their centers and not the left edge as your code assumes. That means that if you have to texels they are not placed at 0 and 0.5 or 0 and 1 but 0.25 and 0.75. It's difficut to assure what happens in 0.5. In short, the nearest texel may not be the one you are expecting (only with two images, my guess is that the 9th square overdraws the 8th). If your hardware supports it, use texelFetch1D, which admits integer coordinates. Maybe adding 0.5 to gl_InstanceID can also do the job.
Finally, remember that 1D textures are limited to 8192 texels in current hardware (at least mine). You'll need a Texture Buffer Object if you need more.
Regards, Juan Jordi Torres wrote:
Hi all, I am trying to show instanced geometry using a texture1D like a vertex buffer. In fact I have it working more or less... but if my Texture 1D is non power of two then my shader does not render some of the instances. Attached is the code and two images, one with a non power of two texture(9 elements) that fails to draw last element, and other with 256 elements that is drawn correctly. I am using TransferFunction1D to pass my geometry array to a texture1D. Anybody knows what I'm doing wrong? Of course I have set texture->setResizeNonPowerOfTwoHint(false); Thank you in advance! Jordi.
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