PDA

View Full Version : Rendering artifact using reflection...



lardbros
09-02-2011, 11:06 AM
I've had this before, and never got resolved, so I'm asking if anyone else has the problem, and what are the ways around it. I don't use Lightwave much, if at all, at work, but I've decided to take on this project in Lightwave and now I'm beginning to regret it a bit.

The data has come from CAD, translated from UG into 3ds max, and then textured etc, then exported using FBX into Lightwave. It all looks okay, even the geometry looks alright and intact.

So I've textured it with a nice nodal anisotropic shader that I created, it looks nice, but I've had some VERY odd issues.

Issue 1
The reflections surface seems to be angular, despite smoothing being on, and all other settings being how they should be. (the surface is curved by the way... Perfectly cylindrical). Now, why does this happen? It doesn't happen in 3ds max. It clearly isn't curving the reflective surface as it should. Is it happening because the geometry has been translated from CAD and is mainly triangles? 3ds max doesn't have this issue at all

Issue 2
One reflective surface is reflecting the same curved piece of geometry, but in the reflection the object's polygons are missing. Not all of them, but every other triangle is missing... And ONLY in the reflection. Now, I managed to figure out it was because Exclude from vstack was off, but why the heck should that make a difference on a non transparent material? The view from which this is happening is inside a transparent material, so I thought maybe it's the ray recursion, but upped that and still have the issue.

They both happen in VPR and standard F9.

Please help! Thanks for listening!

lardbros
09-04-2011, 04:14 AM
Anyone got any help on this? :( Is there anything I can do to the geometry to remove this error in the reflections?

Anyone from Newtek with a comment on the shading of the reflections? Or why it doesn't seem to adhere to the smoothing of the object? Antii?

3DGFXStudios
09-04-2011, 07:26 AM
It's probably a smoothing issue. You can easily resolve this by change the smoothing value to a lower value or by adding a vertexmap. Also you can try to export an obj an see if the smoothing matches the 3dmax looks.

Are some of the triangles flipped?

lardbros
09-04-2011, 09:46 AM
Tried all sorts of values in the smoothing, it's fine in the viewport, so didn't expect any difference in the render. I'll try the vertex vertex map thing... How do I add one? Must have missed that addition. I'll try the obj thing last, I don't really want to alter the whole model again!

lardbros
09-04-2011, 09:51 AM
The triangles are not flipped either... First thing I checked. All points are merged too

Nangleator
09-04-2011, 10:30 AM
Have you Unified polygons? Sounds like it could be overlapping ones.

3DGFXStudios
09-04-2011, 10:52 AM
Can you post a render of the issue?

lardbros
09-05-2011, 04:08 AM
Can you post a render of the issue?

Unfortunately not... It's not for public consumption I'm afraid. I'm going to try and replicate the issue and post them here. Not sure how I can do it, but will try.

I'm certain the mesh is pretty good... Deep Exploration tends to do a pretty good job, but will double check... It's not as good as it used to be and it's been falling behind recently!

Thanks for chiming in everyone... I'll be back later today after some testing!

lardbros
09-05-2011, 08:33 AM
Right... managed to re-create pretty easily... but it seems to be the triple polygons, inherent with CAD translations, that is causing the issue.

This doesn't happen, and shouldn't happen... the same geometry doesn't do this in 3dsmax, so why should Lightwave?

Anyway, merge trigons removes the issue, but I literally have 5000 objects in the scene, and really can't be doing this!

Soooo, any clever bods out there with some techy shading help? :D

Here's a piccy to help illustrate!

Danner
09-05-2011, 08:59 AM
Vertex normal maps are created by other software applications to define where you want smooth or sharp edges. Lightwave can read them on imported objects and you select them in the surface editor at the bottom of the basic properties. They don't render well on classic camera.

lardbros
09-05-2011, 10:31 AM
Vertex normal maps are created by other software applications to define where you want smooth or sharp edges. Lightwave can read them on imported objects and you select them in the surface editor at the bottom of the basic properties. They don't render well on classic camera.

Oh yes... but there is no way to create them in modeller? I've imported them before, but always had to turn them off as they caused worse shading/smoothing errors than having them on.

This isn't just an issue with imported geometry... try it with a simple cylinder created in modeller, and triple it!

toby
09-06-2011, 01:02 AM
Your geometry is a bit low-res to begin with, but mostly it's because tri's are not good for shading or defromations, even in renderman you're supposed to avoid them. Max doesn't have real quads, just tri's glued together with the seam hidden, so they must have tweaked their smoothing accordingly. If your geo doesn't rely on smoothing quite so much, the error is significantly reduced, and you avoid having corners show up where the geo meets the floor, with diffuse shading, or texture mapping.

The only way I was able to solve this was to extend the top and bottom of the cylinder with extrude, and if necessary assign a different shader to the extension, with the same smoothing value but 100% transparency and 0 reflection. If you just have pillars from floor to ceiling it should be easy.

lardbros
09-06-2011, 01:39 AM
This cylinder is low resolution, but it still happens with higher resolution geometry, just its smaller... Not sure this is true is it? Lightwave working better with quads, in layout everything is converted to triangles anyway. Sooooo, why is this happening when they've been converted to triangles manually?

3ds max must have ways of coping with this better, but Lightwave SHOULD be fine shouldn't it? I'll try different keywords methods of exporting from FBX or manually go. In and remove triangles where they are visible.

Unfortunately it's not as easy as pillars from floor to ceiling ceiling... The data I have is from CAD :( Not easy to work with in Lightwave it seems! Last project I try and boast by using Lightwave at work... This has gone terribly!

toby
09-06-2011, 02:10 AM
This cylinder is low resolution, but it still happens with higher resolution geometry, just its smaller... Not sure this is true is it? Exactly true, and if you didn't have straight pillars and a straight reflection you couldn't see it in the first place!


Lightwave working better with quads, in layout everything is converted to triangles anyway. Sooooo, why is this happening when they've been converted to triangles manually?
I believe that the smoothing isn't affected by the final tripling, but only subD's are tripled anyway.

3ds max must have ways of coping with this better, but Lightwave SHOULD be fine shouldn't it? I'll try different keywords methods of exporting from FBX or manually go. In and remove triangles where they are visible.

Unfortunately it's not as easy as pillars from floor to ceiling ceiling... The data I have is from CAD :( Not easy to work with in Lightwave it seems! Last project I try and boast by using Lightwave at work... This has gone terribly!
Yea, you'd expect it to be easier to go from CAD to Max, they're the same company - but don't let them tell you that makes max better! (max blows! :angel:)

archijam
09-06-2011, 02:28 AM
Isn't there a way to generate a vertex map of these objects?
Since they are already tripled, you may have to separate the hard edges (cut paste the top/bottom).

I guess I shouldn't bring up LW's vertex normals, but I can hope ..

lardbros
09-06-2011, 03:46 AM
Exactly true, and if you didn't have straight pillars and a straight reflection you couldn't see it in the first place!


I believe that the smoothing isn't affected by the final tripling, but only subD's are tripled anyway.

Yea, you'd expect it to be easier to go from CAD to Max, they're the same company - but don't let them tell you that makes max better! (max blows! :angel:)

Unfortunately, the CAD software was UG... not anything autodesk related... it was then translated using Deep Exploration, brought into 3dsmax, then exported from there as an FBX! Nightmare of a pipeline, but 3dsmax copes fine...

the more I use Lightwave in our pipeline the harder I find it sometimes. Taking data from other software and into it, especially CAD related data, just causes massive headaches. If you've seen the threads by Lewis on editing and changing materials on CAD datasets in Lightwave, it really ISN'T built for the job.

Seems it's not built for rendering them either though. :(

I've gone in an removed all triangles from the offending parts, but there are many more other issues too... like:

In reflections the geometry is disintegrating when Exclude from Vstack is turned off on the reflection object. This is horrendous... and somehow we need to be able to sort all this out.

lardbros
09-06-2011, 05:38 AM
Isn't there a way to generate a vertex map of these objects?
Since they are already tripled, you may have to separate the hard edges (cut paste the top/bottom).

I guess I shouldn't bring up LW's vertex normals, but I can hope ..

This was kind of the last resort... but yes, it works...

Hope Newtek get the conversion between smoothing within FBX and Lightwave sorted out ASAP... seems this is a BIG issue, especially concerning reflective surfaces.

Anyway, thanks for your help everyone... I'll experiment a little more when I have time, and try and submit a FogBugz so it can maybe get fixed/sorted. It's clearly a smoothing issue, but LW should be able to handle this basic stuff.