displacement triangles appearing on imported geometry

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I've decided to start looking at dreaded displacement in Vray.

All the modelling is done in AutoCAD, with the geometry being imported to max for texturing and rendering. When I use the Vray displace modifier on, say, the brick geometry, I always get dark triangles rendering at intersections with corners etc. Everything else is fine, its just these dark triangles. Anyone have similar issues?

All the vertices are welded, and I've even tried the Meshsmooth with 0 iterations trick but to no avail. I am using 2D displacement with box UVW mapping.

It seems that vray is picking up the edges of triangular polygons. If the geometry is re-created in Max, this doesn't seem to happen. Its just with imported geometry.

[RErender]

V-Ray displacement is dreaded? hehe :P

Anyways the problem is that most of the cad softwares pass horrible meshes to Max (A good argument to do all your modeling in Max). The most common issues are extra vertices/edges and faces. First start by welding the verts of the autocad mesh then if any of the coners don't weld look for extra faces.

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The mesh is quite simple geometry and all the vertices are welded. We cannot rely on MAX modelling as it is not accurate/quick enough for architectural models.

Any other suggestions?

[s0real]

are you importing as 3ds or file linking?

are your normals all facing the right way?

have you checked the 'keep continuity' box on the displacement rollout?

can you post a pic showing the nature of the problem?

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Heres an example. I've removed the brick 'texture' for clarity, but the brick displacement is there.

[s0real]

looks like a .3ds import...

try applying 'optimize' modifier and checking 'auto edge' 'material boundaries' and 'smooth boundaries'

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Its actually a dwg import (from acad 2004 adt to max6). I'll try the optimize thing.

[s0real]

can you file link in max6?

i find that file linked drawings generally come in much 'cleaner' than imported ones...

let us know how you get on.

[blinkimage]

I just tried the opitimize idea but it made no difference.

[RErender]

Looks like it is the smoothing, I would try clearing it .

[stefan]

I´ve seen this even on non-imported geometry in Max 5 with Vray displacement (haven´t used displacement since I switched to Max6 yet though.) This is a general problem with Vray displacement, I haven´t found a solution to it yet.

Stefan

[blinkimage]

tried smoothing to no effect.

could the chaos team comment?

[dbuchhofer]

you would probably have the best luck zipping up a simplified portion of a scene that still has the problem and sending it to them via email..

[RErender]

Hehe, your probably sick of trying my ideas but one more is to try turning some of the edges in the problem area

[Adrian A. Brown]

Just to let you know it is an AutoCAD geometry problem. I've had the same problem. It will render fine with scanline but throw displacement on it and normals problems. I hate to say this but I've yet to find a solution either and I too have tried everything. Like you said the only think that somewhat works is to use 2d disp as opposed to 3d. But obviously with brick you might have problems with separations at the corners.

Vlado, if you do look into it, displaced ACAD geometry will sometimes render completely black as well. Just thought I'd mention it.

A.B.