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Rick Bruce

Quadularity and Texturing Problems?

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  • I read that you should always keep quads in modeling to avoid texturing problems later on, although I read a tutorial where a modeler said he had some triangles in his figure models. My question is (or there a place where I can find this info): what are the problems that arise with having triangles or ngons in your model for texturing? The main reason I ask is that in modeling I find transition of complexity/detail easier to handle if I could use ngons and three sided polys here and there for those transitions. I have been playing around in Bodypaint with ngons and triangles, painting over them in both projection and non-projection painting, straight lines and text and other stuff and so far I cannot see a problem. (Minus animation problems...)

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    Guest dataflow

    iv never heard anyone say tri's and n-gons are bad for texturing.

    only time there bad is when you deform/animate your object (at the bent area's) and then n-gons are only bad if tri's are created from them

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    I would say that tri's and n-gons aren't necessarily a bad thing as regards texturing..unless you are using a HNurbs and animating the mesh,then these polys can create creases and stretches in your mesh which could in turn distort your texture.

    Personally i avoid n-gons entirely,and try to keep tri's to an absolute minimum or hide them somewhere in the mesh they won't be seen,tris can sometimes be very useful for actually creating creases if thats what need though.

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    mala


    I've learned from my mistakes and I'm sure I can repeat them exactly. MacPro3.2+10GB ram+8800GT

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    As Mala says, N-Gons and Tri's aren't a problem for texturing, but they do however create problems for polygon flow when using H-Nurbs.

    Check out this really good explanation here - trust me, it's really worth persevering and reading through the whole thing!

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    There was quite an interesting thread on the modo forums a few days ago, where a texturing problem was actually being caused by quads.

    Or rather, the problem was caused by a difference between the way modo (and Max for that matter) triangulated a mesh for rendering which had been textured in Bodypaint, compared with the way that Bodypaint/Cinema and Lightwave were triangulating the same mesh. Some quads were split on the opposing axis. The outcome was that the poor guy had a mesh with wobbly textures at rendertime.

    Obviously this shouldn't be a problem if you're using one app for texturing and rendering, but it does show a pitfall of having a multi-app pipeline.

    Here's the thread, there's some generally useful info in it: http://forums.luxology.com/discussion/topic.aspx?id=44837

    Mark

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    The same problem occurs just within C4D. It is often better to specifically set the triangulation rather than let the renderer decide.

    You can try this for yourself really easily. Create a cube, make it editable, the select one vertex and move it out. You will then see the problems caused by non-planar quads.

    For animation, you should be aiming for planar quads. If you can't achieve this, put your own tris in where you want them. For animation avoid n-gons. For stills, use n-gons on flat surfaces for modelling efficiency, unless you are exporting the mesh to an application that can't handle n-gons, like Blender.

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    its bull and its always been bull. it comes from when 3d was young and low poly modeling was a necessity. engines could only handle low poly. you essentially had to do low poly. low poly was adopted by everything else outside of engines. because it was viewed as easier to deal with and make. but that really depends on the person. what no one ever says is that a triangular mesh can also be low poly. it doesnt have to be all quads.it animates and textures the exact same way. I could show you models that are triangulated and you would never know from the texture or animation what the topology is

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    The area where tris and n-gons can be a problem is when using sub-d surfaces (HyperNurbs). This due to the way Hypernurbs works. If you look at a subdivided surface, you will notice that the HyperNurbs algorithm creates all quads. This is not a problem when dealing with quads themselves, as it just divides them evenly. However, with a triangle or an n-gon, dividing it into quads makes for a strange poly flow. This can cause shading errors if it occurs on a curved surface. With animations, the deformation of the mesh makes it less predictable where the curved surfaces are going to be.

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  • I would like to see a sample of the shading error of hypernurbs on a curved surface with a triangle. I did notice the odd hypernurbs flow with a triangle or ngon but was unable to see any difference in renders. I ran tests on this face and the real distortions in the shading seemed to occur when polys were stretched too far, like skinny diamonds, and of course differences in size which might show up more if you have a bump texture say for the skin.

    post-28338-126884025708_thumb.png

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    Guest dataflow

    I would like to see a sample of the shading error of hypernurbs on a curved surface with a triangle. I did notice the odd hypernurbs flow with a triangle or ngon but was unable to see any difference in renders. I ran tests on this face and the real distortions in the shading seemed to occur when polys were stretched too far, like skinny diamonds, and of course differences in size which might show up more if you have a bump texture say for the skin.

    it doesnt always happen but trust me it does happen.

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  • I trust you since it sounds likely and there seemed to be a lot of emphasis on keeping things quadular in your figure from the instruction movies I watched about it. The problem of keeping quads is hard for me but I want to make good models for all uses though personally I am interested in fine detail stills for art and design. It is just so far I could not find the problem, but I guess I'll find it sooner or later. I was just now re-modeling my figure so I wanted to see how important it was before I moved on to finishing the project.

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