Displacement issues

[Bosseye]

Morning all,

I've had this problem before, but I don't think anyone was able to help out with it, so I'm hoping this specific topic will focus the great minds of the forum. I've had this issue for numerous versions of SKIndigo/Indigo now, so I'm assuming its a Sketchup problem.

Basically whenever I subdivide a face with a displaced texture on it, I get these glitches in the texture originating at the corners of the cut. I get the same problem regardless of whether I texture the face then cut out the geometry, or if I cut out the geometry first and then texture the face.

Can anyone assist? I can't think of a way around this and currently it means I can't displace textures in walls with anything cut out of it, eg windows.

Thanks in advance.

Displaced texture, no cut out, no error

Displaced texture, cut out added, texture error

[Zom-B]

while that scene renders in Indigo go to the displacement material, set it to diffuse and check on the bottom the checkbox for "random triangle colors" then you'll see the effect of the subdiv you did.
Thats a great base to start debugging

[Bosseye]

Thanks - I've got subdivision set to 9 at the moment, any less and the displacement map looks a little....wrong... for some reason. At that level of subdivision the random triangle option essentially just returns a purple texture

I think I've found a workaround, whether it will always work I'm not sure - if I add a couple more lines in sketchup from the corners of the cut out up the main face of the wall, ie manually subdivide the main face from the cut out then the problem seems to disappear. Not sure why though.

[OnoSendai]

Hi Bosseye,
Can you email me the scene as a PIGS?

Cheers!

[noldo]

I think the problem is related to the triangulation of the face with the hole in the middle.
Try to subdivide the face in sketchup in quad with the same dimension.

[CTZn]

I think I've found a workaround, whether it will always work I'm not sure - if I add a couple more lines in sketchup from the corners of the cut out up the main face of the wall, ie manually subdivide the main face from the cut out then the problem seems to disappear. Not sure why though.

This is the right way to do, construction lines will define the mesh quality before subdivisions.

As noldo suggested, each face of the mesh should be of roughly the same size to keep the level of detail of displacement consistent. Less faces will be created for the same apparent displacement quality. View dependent subdivisions may help a bit otherwise.

Cotty posted a nice illustration some times ago about adding construction lines to a SU model to fix long triangles. In arch viz vertical and horizontal lines are used generally.

[Bosseye]

Hi Bosseye,
Can you email me the scene as a PIGS?

Cheers!

Sorry Ono, I deleted the scene - it was only a swift test one. I can set you up another one and send it if you think it will be useful?

Also thanks to noldo and CTZn, that makes sense to me and the fact that some additional subdivision (manually adding lines) seems to resolve the problem would imply you're correct.

Thanks to all who replied anyway.

[OnoSendai]

Hi Bosseye,
Can you email me the scene as a PIGS?

Cheers!

Sorry Ono, I deleted the scene - it was only a swift test one. I can set you up another one and send it if you think it will be useful?

Also thanks to noldo and CTZn, that makes sense to me and the fact that some additional subdivision (manually adding lines) seems to resolve the problem would imply you're correct.

Thanks to all who replied anyway.

Yes please do!

[Bosseye]

So I recreated the scene and it won't do it now..... All working fine. I haven't done anything differently on this one so not sure why. I haven't even subdivided the main face manually either, its just a hole cut in a wall.

If it happens again I'll email you the scene.

EDIT - maybe its a size thing. I'll try again with a bigger wall, this latest one is a bit smaller than my original scene.

EDIT 2 - Nope, all works fine, even if I make the wall massive. Ah well, forget about it for now. Cheers.

[cotty]

Cotty posted a nice illustration some times ago about adding construction lines to a SU model to fix long triangles. In arch viz vertical and horizontal lines are used generally.

Here it is...