Use Background shader & spot light

# 1 01-01-2013 , 04:39 AM

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I have a question about the Use Background shader and would appreciate help on. I am trying to make a spot light effect render on the surface of a plane with Use Background shader assigned to it. My problem is that when I render, the casted spotlight effect disappears along with the plane.

Anybody know how to make the spot light render without having the plane itself render while using Use background shader? user added image

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# 2 01-01-2013 , 11:21 AM

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Check out Jays free tutorial...................dave

https://simplymaya.com/forum/showthread.php?t=34936

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# 3 01-01-2013 , 06:14 PM

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Thanks Daverave but I have actually already checked out Jay's tutorial, but it doesn't answer my question as to rendering the spot light shape on the plane.

To make things clear here is what I did:

1- I created a polygon plane and assigned UseBackground shader to it
2- created a spot light and oriented it on the plane.
3-Render...

My problem is that the spot light shape disappears along with the plane in the render!!!

Last edited by Vishader; 01-01-2013 at 06:17 PM.

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# 4 01-01-2013 , 08:14 PM

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widen the cone angle

J

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# 5 01-01-2013 , 08:36 PM

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Seems to be working as intended. The default camera background in Maya is black and assigning the useBackground shader to the plane is telling Maya to make this plane disappear into said background, shining a light on it won't make it any more visible. Maybe you could explain your desired end effect as there is most likely a better way to go about it.

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# 6 02-01-2013 , 02:30 AM

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Sorry I forgot to mention that I have an image attached to the camera and wanted only the light effect (Penumbra and cone angle to show) to render, not the plane itself. I don't know if this can ever work!!!... anyone?...

Here may be this will help explain:

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# 7 02-01-2013 , 05:14 PM

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The background shader is only for shadows so will not show you spot light, I wonder if fog would be good for this? or try a lighting layer pass and do some light linking.............dave

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# 8 03-01-2013 , 10:28 PM

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By virtue of what the useBackground does to geometry using it, I don't think it can do what you want. You could render out a matte layer and add that onto the background in post.

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# 9 04-01-2013 , 07:21 PM

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Thanks Gen and everyone. I guess its not possible with a Use Background shader. A matte layer is probably the best way way then.

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# 10 10-01-2013 , 09:17 AM

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i realized why the use background shader was not working. There was no way for it to work, FG affects just the color, doesn't produce a "shadow". I was beating a dead horse:hmm:
Maybe it's possible to trick mental ray into doing a shadow pass out of FG, but i have no ideea how

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