Gobos in Maya - please help!

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Old 11 November 2008   #1
Gobos in Maya - please help!

I have a spotlight with which I want to project a specific shadow shape. But no matter what settings I fiddle with, I simply CANNOT get the shadow (a jpeg image) to project correctly. I just want my jpeg to appear in the centre of the spotlight, and it won't! It's like the size of the image is wrong or something. Is there a specific image size I should use? If not, how do I scale the image to the spotlight size?
 
Old 11 November 2008   #2
Quote:
Originally Posted by zenkatydid
I have a spotlight with which I want to project a specific shadow shape. But no matter what settings I fiddle with, I simply CANNOT get the shadow (a jpeg image) to project correctly. I just want my jpeg to appear in the centre of the spotlight, and it won't! It's like the size of the image is wrong or something. Is there a specific image size I should use? If not, how do I scale the image to the spotlight size?


Don't use a projection or anything, just map a normal 2D file texture to the spotlight's color. The size of the image will exactly fill the size of the cone. If you make the cone angle bigger or smaller, the map will get bigger and smaller with it.

If you use a penumbra angle to make a soft edge, that should be a negative number, so that you don't expand outwards from the cone and reveal a repeat of the map.

If you want the image smaller than the spotlight's cone, you can use the 2D placement parameters.

-jeremy
__________________
Jeremy Birn
Author, Digital Lighting & Rendering, 3rd Edition
 
Old 11 November 2008   #3
sorry, that's what i'm doing now. mapping the colour to a file. but the file seems to be enormous - the spotlight is only displaying a tiny part of the file by default.
 
Old 11 November 2008   #4
So:
Create > Lights > Spot Light
Open Attribute editor
Click mapping icon to right of Color parameter
Make sure "With new texture placement" is checked, and "Normal" is selected under 2D Textures
Click File
Browse for the image
Render and the image fills the spotlight cone. If you make the cone bigger or smaller, the image changes size with it.

Hope this helps,

-jeremy
__________________
Jeremy Birn
Author, Digital Lighting & Rendering, 3rd Edition
 
Old 11 November 2008   #5
yep, that's exactly what i've done. i've just gone through the same steps again, as you wrote them, and still have the same problem. is there some setting hidden anywhere that affects these things? is a jpeg an acceptable file format? any other file format issues/requirements?

thanks heaps for your help!
 
Old 11 November 2008   #6
Quote:
Originally Posted by zenkatydid
yep, that's exactly what i've done. i've just gone through the same steps again, as you wrote them, and still have the same problem. is there some setting hidden anywhere that affects these things? is a jpeg an acceptable file format? any other file format issues/requirements?

thanks heaps for your help!


I just did these things as I wrote them in Maya 2008, using a jpg file as the texture, and it works for me. I don't think that the shape/size of the file matters much, although you could try a different file if you want. If you started with a new spot light, then other options on the light should be at the same defaults as my light. I hope there isn't anything special about the scene (the surface receiving the light, other lights in the scene, etc.) that gives you different results. If the default size matching the cone angle isn't working for you in some way, you could still try adjusting the 2D placement parameters of the file texture. This is something I've done many times, I'm sorry if what I'm posting isn't helping for some reason.

-jeremy
__________________
Jeremy Birn
Author, Digital Lighting & Rendering, 3rd Edition
 
Old 11 November 2008   #7
who knows what i'm doing wrong. thanks for your help, anyway, i'll keep trying
 
Old 11 November 2008   #8
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