Incorrect result when using 3D textures

Question

I\'m using modern OpenGL 4.3 core.

I just realized that 1024p x 1024p tileset is too small for my needs. So, I replaced it with 1024p x 1024p x 4p 3D texture. (I kno

Answer 1

That's because 0 is the "leftmost" part of the left texel and 1 is the rightmost point in the rightmost texel. Assume we have 4 texels, than the coordinates are as follows:

0       1/4      1/2      3/4       1
|  tx1   |  tx2   |  tx3   |  tx4   |

since you need to hit exactly the center of a voxel, you have to use addresses that are 1/2 voxel higher then you expected (+0.25/2 = +0.125), thus the voxel centers are as described in the bottom line of the following diagram.

|  tx1   |  tx2   |  tx3   |  tx4   |
    |        |        |        |
  0.125    0.375     0.625    0.875