CGTalk - Maya 4.5 - strange viewport-only "reversed faces" anomaly

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Jon Jones

01-17-2003, 06:11 AM

http://www.planetquake.com/shattered/shine/images03/maya-wtf02.jpg

Having a weird problem here. Yesterday, out of the blue, Maya suddenly started displaying my models like this. Some objects do this and not others, and I can't figure out what it is or why. I've tried several different scenes and some objects within them will do this while others seem unaffected.

On this particular model, only half of the model seems to be particuarly badly affected. The other half still is to some extent, but not so badly. See image below.

http://www.planetquake.com/shattered/shine/images03/maya-wtf01.jpg

Now, even more peculiar, it renders perfectly, so it's only in the viewports. I haven't installed any new programs or done anything differently. I've tried exporting this as an OBJ and reimporting it to see if that made it go away, and it didn't. Come to think of it, that's when I first noticed it, because the scene this object was in originally wouldn't display the lighting on the model (even though I cycled through the 4567 keys and added\removed lights).

I've also tried reversing normals, which made it look even worse, and I also tried setting face to normals which didn't work.

The UVs are mirrored down the center line, and earlier this week I had another separate problem where the bumpmap would be inverted on the side that's now disappearing the most. That's fixed now, but I found it peculiar that the same side is giving me problems now.

I'm running on an AMD Athlon XP2100+ 1.73GHz w\512mb SDRAM, with my primary monitor on a GeForce 4 MX 440 64mb and my secondary monitor on a GeForce 2 MX 200 32mb, running on Windows 2000 SP3, on a new 80gb Maxtor 7200rpm HD, everything freshly installed less than a month ago. I'm running in 1152x864 @ 75Hz and 32bpp on both monitors.

I've tried switching the primary monitor to the GF2 to see if the problem would go away, but it didn't. I tried tweaking my display settings but to no avail. Maya's worked perfectly fine on this configuration on two different systems (upgraded last month).

Does anyone have any idea what's going on here, and how to fix it? I can't work like this and it's driving me crazy. :shrug:

lowkey

01-17-2003, 07:05 AM

same problem here! :eek:

workaround:
create another cam and use this as your construction camera!

works for me, though it's really strange.

Waboflex

01-17-2003, 12:27 PM

Yeah, seen this a few times, what's happening is Maya's z-sorting in OpenGL is getting screwed up for whatever reason. It works fine in the first image since most front faces are pretty much parallel to the view plane, but as it gets more angled to the viewer it has more trouble sorting poly's. So what all this means is - your camera's buggered :annoyed:

Sometimes it can be fixed, sometimes you just have to do as lowkey said and make a new camera. Before doing that you can try:

- View -> Predefined Bookmarks -> Perspective. Sometimes just 'resetting' the camera works.

- Check your clipping planes in the camera attributes. The near/far should be in the proportion of 1:10,000, but if your scene is very small try making the values smaller, like 0.01 and 100 etc.

- Import the scene instead of Opening it.

You never know, these have worked for me at various times. :shrug:

Wabo.

JasonA

01-17-2003, 05:43 PM

I've recently been having the exact some problem! I have a scene where 5 or 6 parts of my model are "blackened" out like that.

For me, what resets it is reversing the face normals, although you already mentioned it made things worse for you. Anyways, after doing this, everything looked great in the viewports. But even if I save the file and then reopen it, the problem comes back. I'l try lowkey and waboflex's ideas to see if that fixes it. talk about wierd..

lowkey

01-18-2003, 06:49 AM

i think the problem of having 'black polygons' is another issue, demanding a different solution.

i solved it like that, but it didn't help fixing these anomalies we're just talking about!

http://www.cgtalk.com/showthread.php?s=&threadid=29771&highlight=black+polygons

:shrug:

Jon Jones

01-18-2003, 08:32 AM

Okay, thanks for the responses, guys! I tried everyone's suggested fixes, including the ones in that other thread, but I still couldn't get anything to work, so I've still got the same problem. :\

Now what?

Shinobu

01-19-2003, 07:48 AM

eh I've seen this problem on other workstations. its exactly what baboflex said. however replacing the camera usually solves this since most of the time the problem is due to the near far clipping plane. However. when you showed me this model I saw 120 History nodes on it! Jeeze XD most maya modelers deletes thier history every 10 seconds . get a habbit of doing that shine ;3

Shinobu

01-19-2003, 07:52 AM

er correction on my previous post
this is a Transparency Sorting issue. this happens mostly on models with transparency or models with weird material Setups
substitute a blinn material and you will see what I mean. since the model Renders fine, this problem is an OGL issue.

(I have this same problem on my character's hair. its not a big deal )

Shinobu

01-19-2003, 07:56 AM

ARGG I just remembered something right now.

this always happens on models with large alpha maps aswell. reducing the resolution of the alpha or changing its Output resolution fixes this problem aswell..
(under hardware texture quality set it to "highest" its not really the highest but to maya 512x512 is very high. default is Hardware maximum wich is higher than 512x512)

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