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samwu
06-20-2003, 10:41 AM
I tried to apply a texture file to the transparency attribute of my hair shader.
In Maya native renderer, I can get the right alpha channel.
but in Maya v5 Mental Ray which had Final Gather turned on, I wont get the right alpha.
I mean, the transparency attribute seems doesnt work.

any suggestion will be great!

gmask
08-09-2003, 02:51 AM
Originally posted by samwu
I tried to apply a texture file to the transparency attribute of my hair shader.
In Maya native renderer, I can get the right alpha channel.
but in Maya v5 Mental Ray which had Final Gather turned on, I wont get the right alpha.
I mean, the transparency attribute seems doesnt work.

any suggestion will be great!

I'm havinga similair problem ..basically all I get is the profiles of the objects in the alpha channels rather than transparency??

TheGreenGiant
08-09-2003, 09:46 PM
now that you mention it.. I have the same problem. AND i also have problems with my subsurface scattering transparency - It comes out incomplete and only parts of the object is in the alpha channel. Anyone?

gmask
08-09-2003, 09:48 PM
Originally posted by TheGreenGiant
now that you mention it.. I have the same problem. AND i also have problems with my subsurface scattering transparency - It comes out incomplete and only parts of the object is in the alpha channel. Anyone?

Oh I figured out that par tof my problem is that I have a hidden environment sphere that is apparently prevented MR from adding transparency to the object profiles inthe alpha. As a workaround I can render with the maya render and get those transparencies.

TheGreenGiant
08-09-2003, 09:54 PM
Originally posted by gmask
Oh I figured out that par tof my problem is that I have a hidden environment sphere that is apparently prevented MR from adding transparency to the object profiles inthe alpha. As a workaround I can render with the maya render and get those transparencies.

Hmm..

a) How did you discover that sphere - was it just hidden or a hidden node?

b) The choice of doing a second render with maya render take a lot more time - Especially if you plan to do an animation with one of these things needing to be alphaed.

c) does the choice of tif/tga or iff determine alpha quality - I tend to save tifs as render outputs for stills and tga for animations. I encounter the alpha problem with a tif.

gmask
08-09-2003, 09:59 PM
>>a) How did you discover that sphere - was it just hidden or a hidden node?

I created the sphere and had it set the primary visibilty to off but Maya handles the transparency differently than MR I guess??

>>>b) The choice of doing a second render with maya render take a lot more time - Especially if you plan to do an animation with one of these things needing to be alphaed.

In my case it's very fast

>>>>c) does the choice of tif/tga or iff determine alpha quality - I tend to save tifs as render outputs for stills and tga for animations. I encounter the alpha problem with a tif.

Shouldn't make a difference.. just make sure your import the images as either straight or pre-multiplied base don how the alpha was saved.. file format should be irrelevant.

Jozvex
08-10-2003, 07:04 AM
Originally posted by gmask
Oh I figured out that par tof my problem is that I have a hidden environment sphere that is apparently prevented MR from adding transparency to the object profiles inthe alpha. As a workaround I can render with the maya render and get those transparencies.

A much easier way is to just turn down your environment sphere's Matte Opacity to 0, you can find the Matte Opacity slider under the Matte Opacity section of the shader.

:thumbsup:

gmask
08-10-2003, 07:26 AM
Originally posted by Jozvex
A much easier way is to just turn down your environment sphere's Matte Opacity to 0, you can find the Matte Opacity slider under the Matte Opacity section of the shader.

:thumbsup:

Well that works! Thanks:thumbsup:

Any ideas on how to add the luminance from the reflected color to effect the transparency as well?

Jozvex
08-11-2003, 01:52 AM
Err, sorry gmask I don't quite know what you're asking!

:surprised

gmask
08-11-2003, 02:49 AM
Originally posted by Jozvex
Err, sorry gmask I don't quite know what you're asking!

:surprised

If a transparent surface is reflecting a bright color in one area it appears opaque in the color channels but uses a flat transparency in the alpha channel. Usually in compiste I might add the lumiance of a layer to it's own alpha channel to correct for this.

Jozvex
08-11-2003, 06:23 AM
Ohhh ok, I see what you mean.

Hmm, I tried using a Surface Luminance node along with a +/- Average node to add the luminance to the Matte Opacity. It worked fine, but of course I realised that reflections in Maya aren't actual luminance, they're a seperate raytraced attribute or whatever.

So the alpha channel showed the bright areas lit by lights, but not from reflections.

I'm not sure about that one sorry... :shrug:

Spacelord
01-03-2004, 12:49 AM
Originally posted by Jozvex
A much easier way is to just turn down your environment sphere's Matte Opacity to 0, you can find the Matte Opacity slider under the Matte Opacity section of the shader.

:thumbsup:

Hi Jovex,
I'm having the same problems with the enviroment sphere and FG. I have an image of a tree on a plane with an alpha channel on the transparency. On the envirosphere I've set the Matte Opacity slider down to 0 and I still get the envirospheres colour coming through the transparency part of the image. If I set the Matte Opacity to Black Hole and to 0 it works except the FG doesn't work ?
Any ideas ?

Jozvex
01-03-2004, 01:32 AM
Are you talking about the alpha channel of the image you render?

Because if you turn the matte opacity of the environment sphere down to 0 (black colour) everything should be fine.

I've attached an example render. The 'tree' in my render is an image textured onto a square plane, with a transparency map.

Spacelord
01-03-2004, 04:24 AM
Man fast reply !! :)
When I say alpha channel I mean the alpha to make the parts of the plane invisible, not the the finished renders alpha. :)
Checkout my image

I noticed you teach at AIE, I went there years ago, 1997 to be precised.

Jozvex
01-03-2004, 06:51 AM
Ohh right I see what you mean.

Well I've been trying to solve that problem for about 40 minutes now but with virtually no success! I thought I had it for a minute when I turned refraction on for the tree shader but set it's Refraction Limit to 0, but not only did that remove the envirosphere but it also blocked out the other geometry behind the tree.

I'm afraid I have no answer for you on this one!

:hmm:

Originally posted by FuriousD
I noticed you teach at AIE, I went there years ago, 1997 to be precised.

Cool! What a small (or at least well connected) world! I'm basically the fill-in Maya tutor (or at least I was last year hehe).

Spacelord
01-03-2004, 07:03 AM
Thanks for trying :)

Its being a pain, I'm now on my second day trying to figure this out. I think I might comp them in later. I'm sure theres some way to do it in MR.

dweinin
06-22-2004, 09:14 PM
I've think I've seen this question answered before but I did a search and couldn't find it.

I've got a nurbs plane. Mapped with a ansiotropic shader. I've created a black and white ramp map and added that to the transparency attribute. I'm rendering with Maya 6 Mental Ray. When it renders instead of masking out the white areas I get a semi-transparent look. Half opaque and the other half seems to be picking up the specularity, diffusion and such of the shader. Which I want- only I want to completely mask out parts of the shader with the ramp.

How do I do this?

BillSpradlin
06-23-2004, 03:54 AM
Try adjusting your Shadow Atenuation, that should fix the problem.

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