selecting problem

# 1 02-05-2012 , 04:27 PM

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How do I select the surface within the inner circle? I created a nurb and want to assign a blinn only in the inner part (a circular) and assign a blinn with another colour in the outer part (same-centered). Should I have created a nurb sphere, in the first place?

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# 2 02-05-2012 , 05:40 PM

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99% of the time you'll want to use polygons. They're the best supported, and everything is converted to them anyways during render time. If you wanted to stick with NURBS, you would have to cut the surface along the isoparm, so that you have two surfaces. Then you could assign both materials to their separate objects.

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# 3 02-05-2012 , 05:49 PM

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I did it in polygon sphere but the selected surface doesn't have a smooth outline

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# 4 02-05-2012 , 05:56 PM

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99% of the time you'll want to use polygons. They're the best supported, and everything is converted to them anyways during render time. If you wanted to stick with NURBS, you would have to cut the surface along the isoparm, so that you have two surfaces. Then you could assign both materials to their separate objects.

Originally Posted by NextDesign

Which command is for 'cutting' the surface?

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# 5 02-05-2012 , 06:55 PM

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I did it in polygon sphere but the selected surface doesn't have a smooth outline

Originally Posted by sifidis

You need to increase the number of divisions.

To split, see this: https://simplymaya.com/forum/showthread.php?t=7258

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# 6 03-05-2012 , 05:51 AM

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i rendered the nurb object (after i 'detached surface') in mental ray and best quality settings, but it's not perfect round, it's got 'edges' (photo below). why is that?

as for increasing the divisions in polygon mode, i know that, but then again it's got edges again..

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# 7 03-05-2012 , 06:07 AM

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That's because, as I said above, NURBS are translated to polygons on render time. You need to increase the tessellation settings to make it rounder. See here: https://download.autodesk.com/us/maya...mber=d0e573870

as for increasing the divisions in polygon mode, i know that, but then again it's got edges again..

Originally Posted by sifidis

Then you're not going high enough user added image

However, what you're trying to accomplish could be easily achieved through a texture map, or even a ramp.

Imagination is more important than knowledge.

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# 8 03-05-2012 , 06:45 AM

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Yes a texture or ramp would be a good solution for this.

I can help you a bit with the nurbs tessellation however, the method you use depends on the render engine you use. I use mental ray to render nurbs because it has the approximation editor which greatly simplifies the process of optimizing tessellation at render time.

Once again it much more time efficient for me to make a video then try and type out an explanation and grab screen shots...

So bare with me as I whip a video up for you...

"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675

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# 9 03-05-2012 , 08:36 AM

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Here you go. Sorry it came out to 20 minutes. It seems everything I record comes out to 20 minutes lately no matter how hard I try to make it shorter. Hopefully this will give you some useful information on how to use the mental ray approximation editor to dynamically control tessellation at render time.

Mental ray approximation nodes are very powerful for nurbs as well as polygons and subds and is one reason I like to use the mental ray renderer over the maya software renderer.

Here is a link to the video...

https://youtu.be/on7PezD6ND4

"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675

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# 10 03-05-2012 , 03:18 PM

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Hey Rick, nice job! I'm not sure if you know, but Maya has the ability to change the tessellation depending on how close the object is to the camera. See here: https://autodesk.com/us/maya/2011help...mber=d0e617962

Imagination is more important than knowledge.

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# 11 03-05-2012 , 05:53 PM

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Ah no I honestly did not know about that john. Thx I will add it to my notes.

"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675

Last edited by ctbram; 03-05-2012 at 06:33 PM.

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# 12 03-05-2012 , 06:16 PM

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Hey Rick, nice job! I'm not sure if you know, but Maya has the ability to change the tessellation depending on how close the object is to the camera. See here: https://autodesk.com/us/maya/2011help...mber=d0e617962

Originally Posted by NextDesign

Didnt David do some thing on that a little while back?............dave

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# 13 03-05-2012 , 06:22 PM

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I looked at render / nurb's tessellation and I will need to research it further but it seems to be tided to the a small subset of the tessellation attributes of all nurb's surfaces (curvature, u,v division factor, smooth edge and edge swap).

But it's kind of clunky and requires you once again have to tinker with all the tessellation options above in the maya tessellation section of the nurbs attributes on a surface by surface basis.

It does not create a node so you have to set it on a object by object basis. It does not appear to show in the attribute spread sheet which would be nice.

It only applies to nurbs although quick inspection seems to indicate there is an equivalent poly based attribute under polyshape node / tessellation attributes has a "use max edge length" but I am not clear how that would be tided to render camera.

I will certainly experiment with them though just so I understand better how they work in the avent I have to render using maya software, but I think the mental ray approximation node system is more flexible as it can be applied to nurbs, polys, subd's, smoothed, unsmoothed+displacement.

I am glad you pointed it out though as maya is loaded with stuff that can easily get missed and I like to understand all the features and tools.

"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675

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# 14 03-05-2012 , 10:27 PM

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Yep Dave did do a video on the approximation editor. It is a great video but I could not find it. It has a wine glass as the model in it as I recall. I will search for it some more when I get back home tonight and will put the link in here as well.

"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675

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# 15 04-05-2012 , 12:15 AM

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Here you go this is an excellent video on the mental ray approximation for polygon surfaces that Dave put together for us in a free Friday tutorial a little while back. Thanks Dave.

https://simplymaya.com/forum/showthre...+approximation

"If I have seen further it is by standing on the shoulders of giants." Sir Isaac Newton, 1675

Last edited by ctbram; 04-05-2012 at 12:17 AM.

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