[ekatrukha]

Hello Tobias @tpietzsch,

I've looked into the rendering of those border "half pixels" again.
Here is an example (code) comparing two 5x5x5 volumes side-by-side:
"simple" RAI on the left and "multires" on the right (shifted by 5 pixels in X).

They are not identical. The reason is that in the "simple" and "multires" intersection box is calculated as:

intersectBox( mfront.xyz, (mback - mfront).xyz, vec3( 0, 0, 0 ), sourcemax, tnear, tfar );
intersectBox( mfront.xyz, (mback - mfront).xyz, sourcemin, sourcemax, tnear, tfar );

For the source from 0 to N-1 it would span [0; N-1], but it should be [-0.5, N-0.5].

This is the reason why single plane (or just 2D) images are not currently displayed in BVV.

Correcting this for all sampling shaders

intersectBox( mfront.xyz, (mback - mfront).xyz, vec3( -0.5, -0.5, -0.5 ), sourcemax + 0.5, tnear, tfar );
intersectBox( mfront.xyz, (mback - mfront).xyz, sourcemin - 0.5, sourcemax + 0.5, tnear, tfar );

gives:

So either there is no zero padding from (0,0,0), or texture reading in the shader is wrong.
Looking at this code, I think the padding is ok (paddOffset is subtracted from min).
Now, fixing the multires sampling shader finally gives:

I will close my previous PR on this topic.

Cheers,
Eugene

p.s. Working on this, I've noticed the Multibox sources view is not correct, so I've submitted another PR.