TGA alpha not sorting correctly in viewport

[katz3d]

I create textures as 32-bit TGA's, and when I assign a material with that texture to a polygon mesh in Maya (4.0), the model appears to sort backwards, with what should be obscured polygons drawing in front of closer polygons. Maya seems to do this without me telling it to use the transparency/alpha... I'd be just as happy if in Maya it ignored the Alpha channel altogether.

Is there any known fix or work-around for this?

I'm using a GeForce3 Ti... which I know isn't technically supported. And I'm running win2k sp3.

This has been annoying me for some time. Please help!

[gmask]

You need to save the alpha as a seperate file and assing it as a tranpency map or you might beablet o put an inverty node inbtween the alpha conenction and the sahder using the hypergraph and connection editor.

[jeffd]

Or create the texture as a 24-bit TGA.

Or go to the harware texturing of the shader in the attribute editor and set texture quality to highest instead of default.

Of course, none of this is what you want if you want to see alpha transparency in your viewport. If you do, you are out of luck. Alpha polys are hard to sort in 3D. Actually, change that, alpha polys are hard to sort FAST in 3D. I really wish there were sorting options available for the viewports. I wish there were any options for the viewports.

--JeffD

[katz3d]

That actually does what I want... changing the texture quality forces them to sort correctly, but slower and with a slight loss in detail (the seem to get a little blurry). Thanks for the help.

The annoying part is that even though the textures do have alpha channels, I did not tell Maya to use them, which is usually the procedure in other applications (which usually ignore the alpha unless specifically told to use their transparency).

The problem I have with using 24-bit textures (which I had been using up until last week) is that the game engine I'm using requires all textures to have an alpha channel (it only imports 32-bit TGA's). So it just would be a major pain to maintain two sets of TGA files - a maya version and a game-ready version.

...
rich

[jeffd]

We are going through exactly the same thing you describe. We are using alpha channels of the TGA for masking specularity, or an environment map or other stuff. We have bit the bullet and just use the texture quality setting.

This one of the many annoying shortcomings of the Maya viewports. They better get this addressed in Maya5 or MAX is going to end up dominate the games market once again. I just saw a demo of MAX 5 a couple weeks back and they were running DX8/9 shaders in the viewports. It was very cool.

--JeffD

[stebbing]

In Maya 4.5 you can try using the following feature discussed below. I've pasted a quote from the "What's new in Maya 4.5" documentation.
--Randy Stebbing

We've added Transparency Sorting as a menu item in the Shading > Shade Options menu. When turned on, which is the default, if an object is transparent, it will be sorted from back to front in hardware display. The distance used for sorting extends from the camera position to the closest side of bounding box in world space. When you turn it off, the sorting order is then based on the dag hierarchy. This order is reflected in the Outliner window from top-to-bottom.

As an example, you can see this when you have two spheres that overlap each other. As you tumble around them, you can see that they "flip" ordering when Transparency Sorting is on. The flipping is due to the fact that as the camera rotates around the objects, the bounding box that is closest to the camera changes, and the order of the object display changes. When you turn Transparency Sorting off, the flipping stops.