Glow Intensity of one texture affects other textures' glow intensities??

# 1 30-11-2012 , 08:39 PM

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Join Date: Jun 2011

Posts: 17

Glow Intensity of one texture affects other textures' glow intensities??

Can someone please help me understand what the heck is going on here? I'm using Glow Intensity on several textures in my scene. It seems that the glowIntensity value of one object's texture, and/or the object's size, affects how the glow intensity of other objects (with different textures) render. To demonstrate, I made a simple test scene to reproduce the behavior:

Here is the barebones scene with no special effects:
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Here, I increase the glow intensity of the green cube to 0.2. Looks fine.
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Then, I increase the glow intensity of the yellow bar to 0.2 as well. So far so good...
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Here's where it gets hairy. If I increase the intensity of one of them to 0.4, the other object's intensity appears to increase as well! Even though I didn't change the other object's value, and Maya (2011) says that it's still at 0.2!
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And that's not the only way to affect other objects' apparant intensities. Below is a comparison of both objects at 0.2 again, and then all I did was scale the cube down to 0.1. Look what that did to the intensity of the yellow bar:
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Why is it behaving this way and how do I make it stop? It seems like maya is 'compensating' the glow intensities of objects so they don't seem washed out when other objects get too bright(?). Whatever it is, it's totally wrecking my plans.

Any insight is very much appreciated!
Thanks!
d

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# 2 30-11-2012 , 10:55 PM

Technical Director
Join Date: Feb 2004

Posts: 2,988

Hi Daniel, you usually don't want to use Maya's built in glow, as it's simply a post-process. Doing this by hand in a composting application would not only give yourself better control over the result, but get around this problem as well.

As for what the problem is, I would have to do some digging. Could you post the scene file so that I could perform a sanity check?

Imagination is more important than knowledge.

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# 3 30-11-2012 , 11:50 PM

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Join Date: Jun 2011

Posts: 17

Thanks for the advice, Next. Scene file attached.

I figured post-compositing is the proper answer to this issue. Honestly, my After Effects skills are so darn rusty, I've been avoiding that route. I suppose it's time for me to grow up and dive into it like everybody else. But still... this weird behavior is driving me batty. Sure would be nice to know what's going on under the covers here.

Thanks for your help!
d

Attached Files

glowTest.zip (7.6 KB, 324 views)

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# 4 01-12-2012 , 03:20 AM

Registered User
Join Date: Dec 2012

Posts: 5

definitely do it in post, also if you raise the glow of an object, your also creating more light, so even if you didnt raise the glow of an object next to it your still adding more light. a small tip, I find that using incandescence with the color of choice gives you a pretty good lighting effect without the hazing of the glow.

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# 5 01-12-2012 , 03:33 AM

Technical Director
Join Date: Feb 2004

Posts: 2,988

Hey Daniel, I can confirm that I too have the same issue in Maya 2011, so it's most likely a "feature" in the software.

However, just so you know, the Maya software renderer isn't really recommended in many cases, as it's so bare-bones. Glow is really caused by particulate in the air, and the exposure of the camera. Therefore, you can create a nice flow effect using environment fog in something like mentalray, or Vray, incandesence, and gi.

Imagination is more important than knowledge.

Last edited by NextDesign; 01-12-2012 at 04:01 AM.

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