Mental Ray contours

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  05 May 2009
Mental Ray contours

Hello CGSociety! (obviously, this is my first post)

I need some assistance with a project I'm currently on and maybe develop a technique to avoid this in future. So, what am I trying to do is displayed in the following image:

You can see that further away the bridge gets completely "contoured" to black. I'm using distance and normal contrasts to detect edges. If I increase the value in distance I can clear out that but then I get a lack of edges in other places, inside the tube, for example.

I tried to google it but had no luck.
  05 May 2009
I think it's the distance contrast. Only use the normal contrast, and I think it will be better.
  06 June 2009
Yes, that would get rid of that nasty black area, but then some of the other contours would be lost. This image fails to illustrate the problem clearly, but if you would look really close inside the bridge you would see structural features that are parallel and do not trigger the normal contrast. It seems that Mental Ray calculates distance in some weird, non-linear way.

Not to worry though -- it is a still image so I can fix one frame . What I am looking for is a permanent solution (custom contrast shader maybe).
  06 June 2009
That is most likely because your normal contrast attribute, angle, is too large. From what I see that is a quite shallow angle, so your setting needs to be something low for that to register. At least that might be it .
  06 June 2009
I modeled the segments, I know that the faces are parallel. Normal contrast - won't work here. I think that a UV contrast with some sneaky UVs should work here. This is only a temporary solution, I could need to texture models.
  06 June 2009
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