Emission texture and area light

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Rezca
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Emission texture and area light

Post by Rezca » Sun Aug 12, 2012 8:10 pm

I'm sorry if this is in the wrong place, but I'm using Cinema4D to render this so...

Alright. So I have a polygon object outside the window, and an area light in front of it. I was using the standard render before this and thought I'd try working on practicing Indigo with the same scene, and duplicated the file so I could work on it with Indigo without harming the original. From what I know lights in Indigo can't be made invisible to the render and still emit light, so I disabled the area light, and made the background image a Indigo Diffuse material and pasted the texture into the Emission slot so it would provide light.

So far it worked, but it was a bit dark.
emission only.jpg
I re-enabled the area light and moved it behind the dragon and enabled Light Normalization. It was much brighter, but now the emission texture was no longer providing light, and was a solid grey color. Disabling this allowed it to be visible and provide light again.
When I changed the light type to Blackbody, (which I believe is a more accurate light type than RBG?) the texture was a solid grey and did not provide light even with Light Normalization disabled.
The RGB light is just a bit too bright, and changing the gamma did not appear to help much - unless the RGB light's brightness is controlled by the C4D Light's data? It's at 130% there if that affects anything.
emission__blackbody.jpg
This is all with only an emission texture added, if I put the texture into the Color channel as well the texture can be seen with these lights enabled, but it won't provide any light.

I seem to have some problems with Indigo's blackbody light - it's pretty detailed, but if I have two blackbody lights in the same scene, one always seems to "override" the other in terms of color. But that's off-topic.

So I suppose I am asking, am I doing something wrong? Is there a better way to approach this? And should I just use the RGB light type for this scene?
Cinema 4D R13 Visualize + Indigo Render

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Re: Emission texture and area light

Post by Zom-B » Mon Aug 13, 2012 7:15 pm

You are right lights can't be made invisible to camera.

your problem seems to be a massive difference in emitting power of both emitters.

If you use light normalization do it for all lights, to get equal power.
That is the base to start your tweaking from, also use LightLayers for more convenient testing.

textured emitters should have a pure black base color and the texture activated only in the emitter.
Use uniform for fastest rendering (ok, its just 1% faster then others... maybe :lol: ).
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Rezca
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Re: Emission texture and area light

Post by Rezca » Mon Aug 13, 2012 7:52 pm

I'm a bit confused as to what settings change the emission power of textures in Indigo. I think I have it down and then I forget shortly afterwards ^_^;

Anyway your advice of making the base color pure black worked. The texture emits light and is visible even with other lights active now. Thanks!

Unfortunately I only own Indigo RT right now so Light Layers are not available to me :(
I do plan on upgrading when I have the chance. (Saving up for Studio at the moment~)
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Re: Emission texture and area light

Post by Zom-B » Mon Aug 13, 2012 9:58 pm

Rezca wrote:I'm a bit confused as to what settings change the emission power of textures in Indigo. I think I have it down and then I forget shortly afterwards ^_^
Yes, beeing with Indigo since years I don't think its very easy to get into that topic for beginners. I basically use uniform light type all the time and adjust the value to arround 10 to 100k to work nicly with default camera tonemapping.
For very small light sources you'll need to use emission scaling or as I often doo, simply set the emitter to a white color, with higher b value... that multiplies the uniform value, so you can get scale here nicly.
(set the baking rez for such lights to 16x16, since Cindigo will bake C4Ds color Shader to texture on export, and there is no need to go high rez here!)
Rezca wrote:Anyway your advice of making the base color pure black worked. The texture emits light and is visible even with other lights active now. Thanks!
The idea behind that is also that these meshes now don't reflect any light at all (but only emit some) so its even a faster to render, and looks better, not that overblown :)
Rezca wrote:Unfortunately I only own Indigo RT right now so Light Layers are not available to me :(
its really not essential in this case here, but helps a little while testing around :)
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