renderman custom variables not giving the correct subdivision

[pclaes]

Hi,

I'm trying to get some custom attribute from sops to drive the displacement inside a vop rsl displacement shop, but I am getting strange results. It seems as if the "render polygons as subdivision surface" render attribute is not being applied to interpolate between the values.

I've got what I wanted working using mantra, by just checking the render polygons as subdiv.

What am I missing? is there some other render attribute I need to add?

attached two images, the good and the bad. Anyone have a clue - this must be a fairly common thing to do, so I'm sure it can't be that hard.

Edited May 13, 2009 by pclaes

[edward]

You need to edit the Rendering Parameters and add the Polygons as Subdivisions parameter specific to RenderMan,

[pclaes]

You need to edit the Rendering Parameters and add the Polygons as Subdivisions parameter specific to RenderMan,

Thanks, but it's still not working.

I did that, I added it to the object. It should be the correct one, for prman14, but still doesn't work .

I attached the scene.

custom_renderman_attributes_04.hipnc

[brianburke]

Hi pcales

I can't test this as I don't have a PRman lic right now, but I think its necessary to add the ri_subdivscheme attribute.

[edward]

Thanks, but it's still not working.

I did that, I added it to the object. It should be the correct one, for prman14, but still doesn't work .

You attached a non-commercial file. I thought that Apprentice doesn't support rendering to prman?

[pclaes]

You attached a non-commercial file. I thought that Apprentice doesn't support rendering to prman?

Thanks for the suggestions, but still no luck.

In Bournemouth University we have got Educational versions that work like master versions - It allows you to render out with external renderer like prman. No watermarks or other export file restrictions. I guess it's a different type of licensing then the non-commercial version. The scene should be quite easy to rebuild in a Master, just a plane with a custom attribute painted on it, fed into the shader.

I've tried adding the ri_subdivscheme attribute - makes a slight difference, when on Loop it will retopologize the mesh so it looks like triangles rather than quads, but they are still very visible.

I would still like to know why it is not working - but for now I've rebuild my shader in vops and I'm using mantra.

[Alanw]

I've never heard of that licensing before. Wow..

I also don't have access to a prman lic right now, but I can check it out this weekend.

First thing I'd try is to care for your normals a little more.

It's a common technique to calculate a smooth normal by obtaining the difference between the geometric normal (Ng) and the shading normal (N) and adding it to P. Try something like this.

normal Ndiff = normalize(N) - normalize(Ng);

P += magnitude * normalize(N);
N = normalize(calculatenormal(P))+Ndiff;