[poser pro] Why do black lines appear on the 3D model?

Question

3D

The problem is in poser pro, but it seems to me that this is a more global problem,
so the question to all 3D modelers is why do black lines appear?

While I cut it out in Photoshop, I realized that in one case it was black lines, and in the other it was holes.
In 2D, I know that such effects depend on coordinates, but why is this in 3D?
What to do?

Answer 1

As far as I remember Poser, there really can be holes, since the whole model consists of separate pieces joined together. In some cases, I even transferred the model to MAX and stitched everything into one mesh, so that such jambs were not visible on the render.
But that was a long time ago and may no longer be relevant now.