Help with bump and displacement

Hey all… definite newbie with Blender and I’m hoping someone here can help with a problem I’m having. Honestly I’m not sure it’s that big of a problem but you all are smarter than I am at this so I’ll leave it to you…

I’ve been working on re-vising this mesh and I’ve gotten it to a point I’m moderately happy with. Here’s the final render…

When I first started re-texturing the mesh, I had everything mapped to displacement because I like details and accuracy. That’s when I noticed that it was messing up other parts of the object. Here’s what I mean.

This is what the windows on the ship look like with the surface set to bump only.

This is what happens whenever I make the surface “displace” or “displace and bump.” The windows on the saucer section pop out and things go haywire. It looks even worse on final render.

I think I understand that it’s because of the midpoint. However, when I reduce the midpoint, I lose the texture that I need. Specifically I lose the slightly raised areas on the saucer itself, like the areas around the outside of the saucer and the middle sections.

When I switch to bump then the rest of the mesh looks fine and I still have the raised areas on the saucer. So here are the questions…

  1. Is there enough of a difference between bump and displacement in this case for me to even worry about it?
  2. Is there a way to set up the node tree so that setting the surface to displace only affects the area that I’m wanting to be raised while not affecting the windows on that surface and the surface around it?
  3. Would transparent images be the ticket? (My understanding is that they should not have an alpha)

Thanks in advance.

  1. Given the pic you’re showing up top? No, not worth displacement. Just do a test render with bump vs with true displacement-- I think you’ll have a hard time saying that one is better (but the bump ought to be much faster to render since you don’t need as many verts.)

  2. Sure. Whatever you’re sending your bump map, send it something where the windows have a higher value. The same as whatever is surrounding it. (You’d probably be using an image here, so edit the image.)

  3. No, there’s no point to using an alpha channel in your height map.