I was reading the Channel Read/Write section of Programming guide. In 5.4.1 it says we should use
tex3D<int>(gvdb->volIn[in_chan], vox.x, vox.y, vox.z)
While in newer 1.1 version of 5.4.3, it becomes
tex3D<int>(gvdb->volIn[in_chan], vox.x + 0.5f, vox.y + 0.5f, vox.z + 0.5f)
I think it has something to do with the texture filter mode of texture object, but I cannot find the specification anywhere in code or in guide. Personally I have precision trouble using the first line. The second line looks fine so far.