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cheeseskins
05-04-2007, 06:52 PM
I'm making a surface and rendering it in mental Ray and it render fine until I bevel the surface. After beveling the surface I get LARGE black patches all over the model. There not artifacts as their just too big.

I've cleaned the surface, painstakingly checked the surface to make sure there are no 5+ sides faces, all the verts are joined and not overlapping.

I'm using Maya 7, is this problem related to the UV set getting screwed up when the bevel takes effect? If so is it easily fixable and is it an issue that still occurs in 8.5?

I can post some wires render's if need be.

Any help most welcome. Thanks for your time.:thumbsup:

Nick

cheeseskins
05-04-2007, 07:11 PM
I've added a few renders below to illustrate my problem

file:///C:/Documents%20and%20Settings/theDUDE/Desktop/bad%20render.jpgThe good render shows the surface pre-bevel and the image with all the black spots is a render post-bevel. I have included a wireframe for good measure, it is slightly out of date and has a few errors on it that have since been solved but has not solved the overall problem.

I am using simple MR setup with 1 ambient light and a HDRI map and final gather, no GI. The problem occurs if I remove the HDRI lighting and use a simple point light to illuminate the scene. The history has been deleted on the scene.

Thanks

Ironhalo
05-04-2007, 08:38 PM
the error looks like it may be a NAN error? set your output verbosity to progress and see if youre getting a NAN in the output window.

cheeseskins
05-04-2007, 09:08 PM
Ok I'll give that a go, Thanks.:thumbsup:

What is a NAN though, i know it stands for 'not a number' (or summit similar), is it basically an individual final gather ray not returning a value after being 'shot' into the scene? If so how come it only starts happening once the bevel has been applied?

I'll make the surface from scratch again if need be ( :shrug: ) but I'd rather understand the problem in the first place, may help me in the future.:thumbsup:

Thanks again mate.

Ironhalo
05-04-2007, 10:09 PM
honestly im not sure what causes it. i know it has to do with specific models and possibly how theyre created? i ended up remodeling part of an object to fix the problem. it worked. i also had a scenario where i had to break the connection of a mia_material going to the mr shadow slot in the sg node. that fixed it too, even though it really made no sense to me.

i'd guess theres something wrong with the edges your beveling on or somehow the bevels are producing really bad results. try recreating those faces, that may solve the problem.

Diabolos
05-05-2007, 06:27 AM
When you bevel an object, the UV's and normals get destroyed. You are probably getting a pink highlighted error message in the script line during rendering saying something like "Mental ray render has not found a material assigned to polyShape1" or something like that. You need/should remap the UV's on an object that been bevelled. I am not sure if this is what is casuing the artifacts, but you could also check if you have accidentally duplicated the model and two objects are sharing the same space.


D,

cheeseskins
05-05-2007, 07:11 AM
I havn't got two pieces of geometry sharing the same space, Iwish i had though, that would make resolving the problem much easier!

I thought it may have something to do with the UV's. Do I just have to create a new empty UV set? Or is it a bit more involved then that?

Thanks very much.:thumbsup:

cheeseskins
05-05-2007, 09:54 AM
I've now checked the UV map of an unbevelled version of my model and its fine, I've applied the bevel and the UV map is indeed screwed. I've re-built it and it looks similar (identical) to the pre-beveled model.

But guess what???







ITS STILL DOING IT, GRRRRRRRRRRR.:banghead:



Do you think trying rendering it in the latest version of maya (i'm on 7) will solve the problem. So far the UV map seems fine, the geometry is fine, i've deleted and re-set up all the lights and textures, which at this stage are only basic lamberts.

danethomas
05-08-2007, 05:11 AM
I was having this problem earlier.

I had a simple material or shader applied to an object and then if I went to bevel it I would get a whole heap of black and white diagonal lines across it.

It is ineed because the UV's get messed up when you apply the bevel.

I'm only knew to Maya and am still learning it - but I just went up to Create UV's and Planar Mapping and this seemed to fix the problem for me.

Diabolos
05-08-2007, 08:20 AM
Well lets try this.....

Instead of beveling, add some extra edge loops around the edge you would have normally bevelled and then select one edge loop and manually scale it down sort of create your own bevel by hand.

I hope you understand what I mean....

D,

oodle
05-08-2007, 09:32 AM
this might not be a bevel problem, have u try exporting it than rerender it using new scene?

cheeseskins
05-08-2007, 07:58 PM
I was having this problem earlier.

I had a simple material or shader applied to an object and then if I went to bevel it I would get a whole heap of black and white diagonal lines across it.

It is ineed because the UV's get messed up when you apply the bevel.

I'm only knew to Maya and am still learning it - but I just went up to Create UV's and Planar Mapping and this seemed to fix the problem for me.

I rebuilt the UV map and it still didn't work. Annoyingly there are other objects in the scene, also beveled, that work fine!

Well lets try this.....

Instead of beveling, add some extra edge loops around the edge you would have normally bevelled and then select one edge loop and manually scale it down sort of create your own bevel by hand.

I hope you understand what I mean....

D,

I started the object from scratch and that pretty much what I did, looks much better now I've started from scratch, always the way I find. Just need to get the rendering looking good now !!:arteest:

this might not be a bevel problem, have u try exporting it than rerender it using new scene?

Yeah I tried this mate, I know other people have had joy with this approach but not for me im afraid. It's the fact there is seemingly no ryhme or reason for it. Oh well.

Thanks for all your replies dudes, hope it doesnt happen for me or you guys again in the future, 'cause its flippin' annoying.:thumbsup:

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