mental ray vs maya software renderer

# 1 18-05-2014 , 05:15 AM

Registered User
Join Date: Oct 2013

Posts: 3

Hi all,

I am a Maya beginner. Here is what I am confused about:
-polygon object with blinn shader, renders fine in mental ray
-next, within the blin shader, I try applying an image file (jpg with b/w and color) on the diffuse slider to map & modulate amount of diffuse

the result shows up in
- viewport 2.0 ( harware texturing on): luminosity is used to modulate diffuse
- maya software renderer: same here
but not in mental ray ( object renders as before and diffuse map is ignored)

What would be the cause of this?
I tried the same with eccentricity and with similar outcome ( ignored in mental ray, ok in maya software)
further I tried with a png image. Here mental ray use the transparency of the image, but ignores luminosity.

Would this be normal, or am i missing some settings?

Many thanks,

Jill

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# 2 18-05-2014 , 09:37 AM

The thin red line
Join Date: Aug 2009

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Under the file texture node see in the colour balance if "alpha is luminance" is ticked...........dave

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# 3 18-05-2014 , 07:13 PM

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Join Date: Dec 2006

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Posts: 3,522

Can you upload the scene file and texture?

- Genny
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# 4 19-05-2014 , 07:40 AM

Registered User
Join Date: Oct 2013

Posts: 3

Hi all,

"alpha is luminance" under color balance in texture node, was or is indeed key to this problem, thank you daverave.

With this option unchecked, mental ray ignores the file ( although it does appear in viewport 2.0 and rendering using Maya Software). This comes as a surprise as my file is a jpg and does not contain any alpha.

Another strange thing is that I cannot recall having switched this option off.
So I checked starting a new scene, created polygon, added blinn and then a texture in the diffuse slider, and yes for every new scene this is unchecked... I am curious if this is the default or did I manage to unknowingly alter my mysterious settings...? (BTW I tried to trash my ..user/documents/maya.. settings but this didn't help. )

Anyhow, I am very happy that this is sorted out so quickly.

Thank you!

Jill

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