Wireframe render on Sub-D model.

[modoneer]

Hi, I'd like to render out wireframe of my model, and find that V-Ray Edges material renders all trigons on Sub-D models.

How to set the parameter to render polygon wireframe on sub-D models using V-Ray?

Thanks,
Kent

[largil]

Hi,
I am very interested too,

Thanks.

[vladimir.nedev]

You will have to add the V-Ray Geometry Properties package to the mesh item with your Sub-D model.
Then enable either OpenSubdiv or V-Ray Subdivision.

When the native MODO sub-division is used, the MODO API doesn't provide the information how the polygon cage corresponds to sub-divided triangles.
So you are seeing the wire-frame of the sub-divided triangles.

Other situations when you must switch to V-Ray subdivision:
- if you are using the V-Ray PTex texture
- if you are applying a Variation texture in Mesh Parts mode - this is because the MODO sub-division API will slice the mesh into artificial parts that you probably don't want to shade differently

Greetings,
Vladimir Nedev

[modoneer]

Thanks Vladimir!

I also noticed that the wireframe rendered in V-Ray doesn't align with wireframe in MODO, which may due to your saying that MODO API doesn't provide the information how the polygon cage corresponds to sub-divided triangles. In most situations, I can render relatively same model shape by adding one more sub-d level, which means wireframe would be denser but that's fine.

But there are times that I can't add sub-d level:




Kent

[vladimir.nedev]

I forgot about that, with OpenSubdiv you will see the wireframe of the polygons after sub-division is applied.

With 0 as the level, you are not applying any sub-division.
There must be a high vertex polygon in your model, possibly something that loops over itself (for example the letter o would do this), which trips up our OpenSubdiv integration.

Can you try using V-Ray Subdivision ?
Performance wise, it might be worth to enable Static subdivision and displacement near the bottom of the V-Ray Geometry Properties.

In MODO, are you using normal Subdivision or Catmull-Clark (which is the same as OpenSubdiv) ?

Greetings,
Vladimir Nedev

[modoneer]

Thanks!

My model is a normal Catmull-Clark sub-d model.
It works fine with V-Ray subdivision, all wireframe aligned.
I noticed that several edges are rendered heavier than others, which doesn't happen when OpenSubdiv enabled.

I'd checked and quite sure there is one edge on each thicker line.



Kent

[vladimir.nedev]

That might be just how the current edge rendering algorithm works.
One of our developers was looking into writing an improved version, not sure when(if) that might be ready.

It will be nice to have this mesh for testing, both the thick V-Ray edges issue and the OpenSubdiv problems.
If you would like to help us, you can send it to vladimir.nedev [at] chaosgroup.com

Greetings,
Vladimir Nedev

[modoneer]

No Problem. Project sent.

Kent

[vladimir.nedev]

Thank you for the scene.

Greetings,
Vladimir Nedev

[vladimir.nedev]

The problem with OpenSubdiv is caused by my export code. There is a curve in the mesh that confuses it.
If you delete the curve, the OpenSubdiv sub-division will work correctly.
The edges seem to look much nicer with 1 level of OpenSubdiv.



Greetings,
Vladimir Nedev

[modoneer]

I noticed you enabled OpenSubdiv and V-Ray Subdivision simultaneously.
Why do you check both than just choosing one of them?

Besides, would you please tell me which curve cause that problem. It might be helpful avoid doing it again when modeling.

Thanks,
Kent

[vladimir.nedev]

I noticed you enabled OpenSubdiv and V-Ray Subdivision simultaneously.
Why do you check both than just choosing one of them?

I checked OpenSubdiv to subdivide the mesh a little so the V-Ray Edges textures would work better, to get edges with more consistent thickness.
I checked V-Ray Subdivison, because with OpenSubdiv, the V-Ray Edges texture always shows the final subdivided polygons.

Besides, would you please tell me which curve cause that problem. It might be helpful avoid doing it again when modeling.

When I fix it, you won't have to avoid it.
But for now:


Greetings,
Vladimir Nedev