SDK Volume Render Texture Normalization of the Texture

Accelerated Computing CUDA CUDA Programming and Performance
1

Hi all,

I am newer cuda-programmer and apologize in advance if I posted this in the wrong place…

My question has to do with the CUDA SDK Volume Render.

When the values from the Bucky.raw file are stored in the texture, I am unsure how they are normalized. I am modifying it for my research and need to check the value that the sample receives to coordinate my transfer function. I know the values are clamped between [0,1], but I am a little unsure how they are clamped before being stored in the texture.

Any help would be GREATLY appreciated :)

2

Hey onorinbejasus,

at first you have the data as unsigned char type. Then you initialize texture

texture<VolumeType, 3, cudaReadModeNormalizedFloat> tex;

with this data array. Attribute cudaReadModeNormalizedFloat defines read float data as normalized.

So at last you can read data from texture as float:

float sample = tex3D(tex, pos.x0.5f+0.5f, pos.y0.5f+0.5f, pos.z*0.5f+0.5f);

You can use cudaReadModeElementType instead cudaReadModeNormalizedFloat, then read data will not be normalized.

3

Thank you so much for the reply! So I am getting the correct values in the range I expected. I just have one last question. Are this values in anyway interpolated when they are returned to me? In other words, are the values I am getting the ones I entered?

4

Yep, they are interpolated. You can choose appropriate interpolation mode with filterMode attribute - cudaFilterModeLinear or cudaFilterModeLinear.