displacement triangles appearing on imported geometry

[dennis]

subdivide anyone ?....did you try to put a subdivide modifier on top of it and did it work ?

[Rolojero]

yes subdivide, convert to almost anything, import, file link manager, standard material, vray, blend material, almost everything.... i think

so if there is no hope for us autocad modelers...

let us know in a gently way...

[dapeter]

I had one tricky wall on the last project I did (AutoCAD file link into viz 2006 using vray 1.46.15) where the subdivide modifier left a triangle artifact on the wall similar to what's shown on the grass image above.

All I did was go through and slice the wall / connect verts until the mesh itself looked good. If you're having problems (I have had NONE at all with vray displacement) then you need to go in and clean up the mesh somewhat manually. If you're getting artifacts like the infamous 'dark triangles' then add an edit poly modifier on the object, go into "Edge" mode and click "Edit Tri." You'll probably see a dashed line representing the edge of the 'dark triangle' you get in the rendering. This is because Viz seems to attempt to connect edges in surfaces to the nearest vertex instead of spreading the connections out properly. And I don't mean actually connect, I mean the hidden connection that's in any poly with over 3 vertices.

So, in the grass above, what ends up happening is the verts on the hole are not actually connected to the outside of the plane. It seems like when Vray displaces the hidden edges between the hole and the outer edge it doesn't split the edge properly (although if it's an actual connection there's no problems).

So, if I get a dark triangle, I go in and manually connect the offending vertices until the mesh has more smooth, regular connections to the hole. For instance, every now and then a wall will come in with windows where displacement causes the dark triangles. I'll add an editpoly modifier on the stack, and then use Quickslice from the front view, snapping the quickslice to the corners of the window and making, in the end, a tic-tac-toe like pattern around the window. This way, when you look at the mesh after the editpoly/quickslice has been done, there are individual polygons surrounding the hole in the wall. Then I'll add a subdivide modifier on top of that just to break the straight edges up and give the vraydisplacementmod some extra tri's to start from.

One thing I've found, though, is if you have a wall file-linked and then do the editpoly/quickslice, then subdivide, if you refresh the file link Viz will assign new ID numbers to the subdivided polygons (messing up any multi-sub materials on the wall)... doing the edits, adding the subdivide modifier and making sure it's set to 'manual' seems to be a way around this.

[panthon]

Hi!

I found the same problem with a large displaced grass area, with triangles here and there, Ngon polys and stuff. Displacement was showing nasty shadowed irregular areas, so I applied a subdivide (not smooth or meshsmooth) modifier with a low value on size parameter and got a fairly divided mesh, much more than original. The problem went away and displacement rendered correctly. I must say it was 3d displacement. It´s important to notice that meshsmooth and turbosmooth will do nothing but harm to a not-turbosmooth-ready mesh, because u need to follow some rules so that your mesh smoothes properly.

I read somewhere in the forum that 3d displacement needs an initial amount of faces on your mesh in order to work the right way, because large areas with a single polygon aren´t the ones displacement prefers... Can anyone confirm it?

[vlado]

I read somewhere in the forum that 3d displacement needs an initial amount of faces on your mesh in order to work the right way, because large areas with a single polygon aren´t the ones displacement prefers... Can anyone confirm it?

That is correct.

Best regards,
Vlado

[tricky]

Blimey! Has this come up again. I started this thread a few years ago and its still going! The strange thing is, I have just had a call from that very same client who wants another job doing!

Weird.

[tricky]

I know, an old thread, but I still get these problems! Its one of the main reasons we very very rarely use vray displacement, but I am convinced it can be solved.

I have tried applying a subdivide modifier on top of the file linked geometry, and set it to about 5m or so. After doing this, the dark traiangles appear everywhere that there is a 5m triangle edge.

I had hoped that SP3 would work better with file linked geometry, but at the moment, it seems not. What I don't want to do is have an editpoly or an editmesh modifier on the file linked geometry, as doing this in effect breaks the link between ADT and Max (ie updates to the 3D model in ADT will not be updated in Max unless the editpoly/mesh modifier is removed).

I will try a few other things, but can anyone suggest a good fix for this after all these years?

[Da_elf]

also doesnt vray behave better with quads rather that tri meshes?

[^Lele^]

not really, afaik.
The new sp3 quad splitting method though is a lot better at handling wildly varying triangle sizes that the old binary method used to be.
It feels a lot more resilient and adaptive than the old.

[jacksc02]

tricky, if you upload the mesh that is causing the problems im sure someone will find the issue quickly.

[werticus]

I was having this issue and setting tight bounds to off and continuity to off, and split method to binary fixed it.

It was with an exported 3ds from a client so not sure how they made it, probably archicad or some such thing.

However i got the same problem when i remade the mesh from the start...

also subdivide works