Change Light Shape of Spotlight or fine-tune decay of Point Lights (Maya, MR)

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Old 12 December 2005   #1
Question Change Light Shape of Spotlight or fine-tune decay of Point Light (Maya, Mental Ray)

Hi! I've been struggling with the Decay Rate of Point Lights and would like to adjust them in the same manner as is possible with Spot Lights, i.e. as with the Graph Editor or similarly. I know the documentation sais that this simple approach is not possible, but I've heard that there are some work-arounds.

One of my ideas is to use six Spot Lights which all have a 90 degree Cone Angle and are positioned and rotated to mimic a Point Light. My problem with this is that the default Light Shape of Spot Lights is circular, and it needs to be quadratic in this case. I'm not sure this method will meet my needs but I'd like to try it anyway.

Maybe there is another method available through the Connection Editor? It would be great if it's possible to link a graph to a Point Light's Decay Rate node.

I really need a good method to be able to do this, and it's preferrable to know a technique which can be reused in many situations. I'd like to avoid methods which are time consuming or that overloads the rendering process.

I am thankful for all guides, suggestions and tips related to Light Decay. Please give simple and complete answers, since I am not used to all aspects of Maya's interface yet (I've been using 3DS Max before). Note! Please don't describe how to adjust the Decay Rate with the predefined steps (Linear, Quadratic, and Cubic). I would'nt have written here to know that.

For those who does'nt remember or know how to customly adjust the Decay Rate of a Spotlight, I've added a simple guide:

(This is also described similarily in the help files for Maya).

To adjust the Decay Rate of a Spotlight with the Graph Editor:
- select a spotlight (press "t" to see its manipulator)
- Light Effects > intensity curve > [>]
- lightInfo > Turn on Light Direction Only
- Windows > Animation Editors > Graph Editor
- intensity curves are dark blue lines, while colour curves are red, green, and blue lines
- use the middle mouse button to adjust the points on the graph
- use IPR-rendering to instantly see the results

Last edited by Samarts : 12 December 2005 at 04:01 PM.
 
Old 12 December 2005   #2
Maybe try 2 spot lights:
Cone Angle: 179.5
Penumbra Angle: 1

Do that help?

-jeremy
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Jeremy Birn
Author, Digital Lighting & Rendering, 3rd Edition
 
Old 12 December 2005   #3
Assign a MentalRay MIB_PointLight to your light's MI Custom Shaders.

In the Shader's Properties you'll find the good old Start and End Falloff.

The values are in Units. So 1 = 1 Maya Unit.

This is exactly what you want.

This works on a Spotlight as well...use MIB_Spotlight instead.



.
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PPGingras
Sr Lighting Artist.
Ubisoft Inc.

Last edited by PPGINGRAS : 12 December 2005 at 06:21 PM.
 
Old 12 December 2005   #4
I included a PointLight rig...

Simply control the Falloff by Translating the Locators in local X.


Cheers




.
Attached Files
File Type: zip MIB_PointLight_Rig.zip (6.4 KB, 12 views)
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PPGingras
Sr Lighting Artist.
Ubisoft Inc.
 
Old 12 December 2005   #5
Build a spot light, create the Intesity Curve under the light effects of the spot light, then change the light to be a point light. The Intensity curve will be still connected to this point light.

I have to say that I have never really liked this method when I was begin to learn how to light scenes. But I have to say that if you want to control a curve for the ligth intensity this is a quick way to do it.
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Old 12 December 2005   #6
I think a Light Intensity Curve offers more control if you need the light emission to have multiple falloff. (Start, stop, start again, stop...etc...).

But using a MIB_Point or MIB_Spot is way more intuitive and efficiant.

Anyways...each is own methods.




.
__________________
PPGingras
Sr Lighting Artist.
Ubisoft Inc.
 
Old 12 December 2005   #7
Originally Posted by PPGINGRAS: I think a Light Intensity Curve offers more control if you need the light emission to have multiple falloff. (Start, stop, start again, stop...etc...).

But using a MIB_Point or MIB_Spot is way more intuitive and efficiant.

Anyways...each is own methods.




.


Couldn't agree with you more. Just figured I post the information. I have to say that I have never really been on for the method I described, but it does enable the fall control, its far less intuitive. Remember spending so much time playing with it after the instructor showed me and thought it was lame because the light falloff was so hard to control in some ways.
So I just stick with the standard decays. Gonna give you method a try.
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Old 12 December 2005   #8
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