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Question about Iray, sub-D, and uvs

3WC3WC Posts: 1,107
in Technical Help (nuts n bolts)

I'm having an odd problem, illustrated by the screen caps below. Notice the gear in base resolution, textures look fine. However, when applying subdivision, textures start to look distorted. Renders in 3delight, however, look just fine, so I figured it was just a glitch with the subd preview.

image
(Fig. 1 Base resolution)

image
(Fig. 2 Base render 3DL)

image
(Fig. 3 Hi-res distortion)

Iray renders, however, retain the weirdness when rendering. It's not a good render, because I had 3delight materials still applied, but you can see the texture distortion.

image
(Fig. 4 Iray render retains uv/texture distortion)

Anyone know what's causing this and how it can be fixed?

Thanks.

Base.jpg
603 x 543 - 162K
BaseRender.jpg
479 x 538 - 192K
HiRes.jpg
560 x 587 - 169K
HiResIrayRender.jpg
522 x 539 - 116K

Comments

  • mjc1016mjc1016 Posts: 15,001

    At the very least you need to set 'sharp edges and corners' under Mesh Resolution, in the parameters.  I would add bevels/edge loops/someting (more faces to being with) to the gear, first (and still set sharp edges & corners).

  • 3WC3WC Posts: 1,107
    mjc1016 said:

    At the very least you need to set 'sharp edges and corners' under Mesh Resolution, in the parameters.  I would add bevels/edge loops/someting (more faces to being with) to the gear, first (and still set sharp edges & corners).

    That's not really my concern.  I don't care if the mesh is smooth, I'm just wondering why the texture is weird.  And only in the Iray render, not the 3delight render.  And, as an extra detail, only on the left side and not on the right side.  I've checked all the uv mapping, that all looks fine.  And if that were the issue i would think it would show up in the 3delight render also.

  • mjc1016mjc1016 Posts: 15,001

    I don't see a 3DL hires render...

    The distortion is because the mesh is not keeping clean edges when subdividing.  I'm guessing the worst part is on the back, where you can't see it...it looks like the texture map is being pulled up over the top and down the back...

  • 3WC3WC Posts: 1,107

    Yeah, definitely something up with the mesh.  I took it back into blender, and even with a subdivision modifier there it looked a little strange.  Anyway, as a quick fix, since the gear on the right arm didn't have the problem, I just copied and mirrored it over, and done.

    Thanks, mjc1016.

  • mjc1016mjc1016 Posts: 15,001

    If mirroring worked...then there is something wrong with the basic geometry on that side...possibly an extra vert or face.  A single vert can really screw up subdividing.   Looking a bit more, I'm thinking that maybe one of the verts on the backside got welded to the arm.

  • 3WC3WC Posts: 1,107

    Its possible, looking closely the subd in DS was even splitting the mesh in at least one place. So something wasnt right, and instead of trying to figure it out, I went for the easy fix and just copied the good side. yes

  • mjc1016mjc1016 Posts: 15,001
    wwes said:

    Its possible, looking closely the subd in DS was even splitting the mesh in at least one place. So something wasnt right, and instead of trying to figure it out, I went for the easy fix and just copied the good side. yes

    If it was splitting then it's even more likely that something wasn't quite right at the vertex level.

    But I've done the mirror the good side more than once...it's a very valid modeling technique.

  • Cris PalominoCris Palomino Posts: 11,391

    What do your UVs look like?  Do you use a colored/numbered grid when you UV map?  This is a good way to check for texture distortion.  It would tell you if your distortion is due to the way you UVd or something else.

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