GPU based Volume Rendering issue -shift intensity values

Dear GPU programmers,

I am currently working on Volume Rendering using GPU Volume Rendering. We use GLSL shader language for all our Volume Rendering applications using 3D Textured Mapping Technique.

Recently we encountered a small problem which is eating our core work.


We have a dataset of 128128128. Our the slices consist of border values as 2048.
But When we rendered the volume there is shift in the intensity of the pixels. Border values
are rendered as pixel value 8 and one but border values have pixel intensity 2040.
(2048 = 2040 + 8 ) .When we changed value of the border to 200 we get the value as 1 (border pixel)
and one but border pixel as 199. (200 = 199 + 1). In both case one actual border value is 0.

We then changed the texture coordinate from (0,1) to ( 1/2 * no of slices, 1-1/no of slices ) as per GPU Gems 2 ( Page 387).

Still the problem persists. The interpolation technique we are using LINEAR. But when we use
POINT as the interpolation the problem disappears at the cost of some unwanted probem.

What might be inherent reason. How to overcome this issue.


Which hardware are you using?

At which texture coordinates do you expect to sample the texture border, and at which coordinates do you expect to sample the leftmost and rightmost texels in the texture exactly?

Note that it should be (1 / (2 * # of slices), 1 - 1 / (2 * # of slices))

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