Bad tessellation or what?

[stallion151]

i don't think that would be possible, since they're two completely different surfaces with no connection. You could try to match them but i don't think you ever get them exact. I could be wrong but i haven't heard about that.

For the viewport display, you'll need Nurbs Surface Display>Crv Precision Shaded> more than four is good.
That is just viewport.

With Tesselation if you enable Primary and Secondary Tesselation Attributes, you get so much more control over how it will calculate.
So maybe there you'll find you answer on how to match points.

Good Luck.

[Jakobud]

Is that polys that you are using? Looks like it... anyways, the only way to get the edges the match up is to do in manually. It's not as difficult or time consuming as you might think. The two poly objects do NOT have to be combined. They can be seperate. Its' just important for both edges to have the same number of spans and have the vertices of one edge snapped to the corresponding vertices of the other. This will give a crisp hole-free connection between the edges. You will probably have to split some polys here and there. You should check out a set up scripts called MJPolyTools. They are handy for polygon editing, especially when it comes to setting up clean parameterization like you need here.

[stallion151]

those aren't poly's

"These surfaces are circle planar surface and circular fillet"

[kyvadlo]

There must be some solution . I can do that in the rhinoceros program (it si the join function) but maya is a little bit complicated...
this is a second forum where I send my question and still don`t get the answer.

[squeige]

did u try rendering yet??
nurbs tesselate a lil diff when u render, also go into attribute editor under the planar cap surface and change tesselation attributes, do a display render tesselation and make sure that u get the detail small enough to match the other surface issos to some degree

[squeige]

send me a sample scene ill help you
squeige@msn.com

[wrend]

its unlikely you'll ever get them to match if they dont share the same paramterisation, especially if one is trimmed. evidently maya is really poor at dealing with tesselation across boundaries, it doesnt even look to see if they are any, so there wont be any nice holding hands, you have explicitly set it up yourself. and the only sure fire way to get matched tesselation across independent patches/surfaces is to match their paramterisation, then their tesselation method. otherwise, you can just get the triangular approximation of the edges as close to each other as possible, and have antialiasing spot out the crack dots that may apear in render. in your example, you could make it one surface by extending the non-planar piece out and pinching it in to a cat's arse, or to patch it up you might extract the outer curve of that surface, cut it symmetrically in 4 if you can and make a boundary surf out of it. or render it in an app that handles tesselation better (or uses some subpixel method)... how does mental ray fair?

[kyvadlo]

A t first thanks for replys, I really appreciate that

I know that the tessellation problem that I have look simply for first look but believe me it is NOT. I tried both tesselation primary and secondary too. (long time ago) this is my very old problem.
The surfaces on the pricture are only examples to describe problem that I have. I only wanted to show how maya is unable to solve basic rendermesh nurb problem, I know that surfaces are trimmed (not the same parametrisation) but when you work with nurbs on more technicall loooking objects (robots atc..) you must trimm very often. I thing that problem is in the Maya, I started to believe that maya doesnt have any similiar function like rhinoceros to make connected rendermesh on the borders of two touching trimmed surfaces
last thing: I work with maya 1 year and this tessellation is worst thing on maya I had ever seen.

squeige: I turned on displey render mesh already. Surfaces on the picture are showed with render mesh (not displey mesh)
and you can try to set up the "right tessellation" (primary and secondary too) but you will never get nice looking rendermesh without little holes in the touching area between surfaces.


wrend: hmm ... the same parametrisation of the surfaces is the key to nice connected render meshes .. I thought so too. WRONG.
I believed that the trimmed surfaces cannot have connected render meshses across boundaries (where they are touching) unless I tried rhinoceros :) for this program it is no problem to connect Render meshes of the trimmed borders of the nurbs . And btw rhino 849$ and maya 6000$

Sorry for that but Maya nurbs sucks what else can I say

But when I forgot these thing about nurbs, Maya is the best program I ever worked with. I only wanted to proof myself that problem is not in me but in the program. When you don`t think so
than explain me this tesselation problem please.

[JasonA]

yes, Maya's lacking of a 'join' feature is extemely unfortunate, and frankly i don't think there is a workaround for it. I've seen billions of 'tesselation problem' type posts and the responses are always the same - match up the parametrization (works, but is almost impossible to do on complex industrial surfaces) or tweak the tesselation values (which rarely solves the problem). I've been fighting this for months, and to no avail.

Basically, maya nurbs is not a very good solution for complex industrial object rendering. Its best for organic, flowing shapes - period. its not a fault of the modeling tools per se (although the lack of chamfer tool for nurbs is odd) causwe the tools between Rhino and Maya are very similair, its a fault of the tesselation methods maya uses. Rhino's Join feature makes sure two surfaces get tesselated properly to appear as one flowing surface. Maya just doesn't have it, so you always get the gaps.

I have found tho that rendering the surfaces in Mental ray sometimes closes gaps that the default renderer leaves open, but its not foolproof either from what I've found. If anyone has the smoking gun on this, I'm sure many maya users out there would be etternally grateful.

[wrend]

yep, right on. maybe not nurbs as a whole, but their boundary tesselation method (or lack there of) suck. but thats for their native renderer, jason is having some success letting mental ray do the tessealtion. or if you use a renderer running on the renderman spec? they dont tesselate their parametric surfaces? as jason is saying, the kind of connected boundary rendermesh you talk of is more the province of engineering type apps than the 'entertainment' breed - does alias Studio tools handle them correctly? and if so, why wont they friggin integrate it into maya too? (as an option, if it brings too much overhead).

even once you've sorted out the tesselation to match and you have no more gaps (ie, you've patched your model up correctly, and explicitly matched your tesselation - which usually means you've throw away any benefit you might have got from adaptive, curvature based tesselation of your nice nurbs), you still get what i refer to as 'specular seams' across tangent continuous boundaries. making them curvature continuous can usually alleviate the problem, but not always, and how often do you want, or can even afford to handle such surfaces? do other apps suffer from this specular seam? anybody got thoughts on this?

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