Getting mad with Maya's inaccuracy


#1

Hi,

Well my Problem is, that somehow Maya works too inaccurate for my taste. I dont know if the operations in Maya can be made even more precise by changing some options, but all my “tolerance” sliders are at 0.0000 already.
Look at this one:

Plz go to http://de.geocities.com/cshapeshifter/ and then click on hole.jpg

Everything is done in NURBS, a sphere (1) intersects with somekind of cylinder (2), then with another stretched sphere (3) and last with a long plane (4). I’ve done this, so that the sphere is visible all the way through the 3 other surfaces. I made these intersections and then trimmed the useless things away. Everything seemed ok.
But you see in the render two thin gaps on the sphere, one caused by unaccuracy on the intersection with the sphere (3), and the other, shorter one by the unaccuracy on the instersection with the Plane (4).

I looked very close at the sphere (1) and these gaps seem to be caused by the other surfaces coming to mach in the sphere.

This is really really annoying, because I want to make perfect NURBS-Objects, and like I said, all the tolerances are at total 0. But it seems that maya cant calculate these operations accurate enough.

I hope, that these gaps are caused by me, and not by this expensive piece of software. I really hope that I just have to turn some options higher somewhere, and that you can help me.

Thanks in advantage,

TB2

*edit: and oh, i forgot, I use extremly high tesselations on these renders.


#2

I think you can do 2 thing!

one, take object one, and go to “Display” and make it show it’s CV’s, then take object two and go into the CV’s and select a CV, and press “V” for pointsnapping. Pointsnap the CV to the opposit CV located on object one. You may have to edit the object to be sure they have the same amount of isoparms and paramitersation.

two, You could connect the objects and weld them together.

Hope this can help :thumbsup:


#3

erm, I dont really understand your recommendation and how cv-snapping should work on this. the cvs of the sphere are somewhere outside of it, and dont have any thing to do with the other cvs. And I dont know how the trims are controlled there, I think they are controlled by the intersections, but it seems that they are unaccurate, cos the trim didn’t take place exact on the sphere, but a bit to far in the sphere.


#4

That is definatly a tesselation error. I know you allready said that you have very high tesselation on it. Did you look at the actual tesselation to see if it has gaps between the two when it turns them to polys?


#5

Yep, I turned display render tesselation on. Or is there another option i have to turn on?


#6

Just turning on show tesselation does nothing, it just shows it. You need to turn on the overrides and actually turn up the tesselation.


#7

yeah I turned U factor to 10 and V factor to 20 - really high tesselations, and then choose highest quality on curvature tolerance, and then display render tesselation.
Here’s a screenshot of the plane, that comes into the sphere. That shouldnt happen, if the intersection would have been accurate.

plz go to http://de.geocities.com/cshapeshifter/ and click on gapwired.gif.


#8

Can you show a screen shot of the tesselated wire zoomed out more. Im not sure what Im looking at in that pic.


#9

http://www.animagraph.com.br/DeathBrain/Modeling/Fillet_Trim_Tutorial.htm


#10

Maya’s tesselation does not consider the tesselation of adjacent surfaces, so the best you can do is increase the tesselation of both and hope that these gaps or overlaps are not visible in the final render. If you want something to be perfectly welded at the seams, then you will need to convert to polys (or maybe sub-d’s) so that you can make sure the edges align percetly.

In some cases you can build nurbs patches so that they have identical parametisation on adjacent edges, but in my experience, this is difficult to preserve and puts constraints on your modelling. Not worth the trouble in my opinion.

I remember reading that Rhino handled this problem much better, but I have never used it.


#11

Try setting your renderer to Mental Ray. I haven’t been doing a Nurbs model lately but I seem to have an easier time with tessallation when using Mental Ray as the renderer. It seems to render faster also.

-jscott


#12

yep, its exactly like djx said. its sad maya doesnt have this capability, which is often the province of engineering apps, …especially sad given that alias produce studio tools, which, apparently, does have this technology …why they cant port it to maya as an option? guess enuf people havent asked for it.


#13

from my experience you alwasy get the tesselation right in maya if you build the surface right. That may take some time but it should work. try the advanced tesselation cause i got much nicer results with it. but as someone already said this works much faster in mental ray.


#14

yeah i agree with atzfratz. If you can give us some indication of what this object actually is without having to decypher your list we may be able to suggest better ways to build it.


#15

Ok, I’ve uploaded three other large screenshots.

They’re on http://de.geocities.com/cshapeshifter/ and called wiredhightesselation1, 2, and 3.jpg

  1. A persp, showing all the parts, numbered like on the rendered picture.
  2. A side/front/top/persp view of these things with the spheres (1) and (3) selected.
  3. The Surface (4) coming into the sphere, like it shouldn’t. The Surface is selected, and the area marked with red is zoomed in in the grey box on the right. There you can see how the surface is coming too much into the sphere. And thats why it looks like a gap in the sphere if rendered.

On all Screenshots there are used very high tesselations, like you can see in the attribute editor.

And I maybe can describe my problem a bit simpler;
I just want to put a Sphere in this cylinder. And the sphere should be empty. And thats why I intersected it with other surfaces, witch are covering the sphere, and trimmed the useless surfaces away.

And excuse me for my really bad english…


#16

your website exceeded its bandwidth or some such thing.


#17

:argh: I HATE YAHOO. Man… Well… I’ll wait until the traffic isn’t blocked anymore and get the thread up again then…


#18

Well anyway, I deleted this bunch of intersections and trims, and built the cylinder and the sphere out of revolved curves. then I projected some curves on the other parts, that were bigger then those, and trimmed. so that nothing intersects with another anymore.

Thanks anyway for your help,

TB2


#19

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