Light Decay and Spread

[zmuh11]

Will turning down the intensity from the area light outside the window or the main spotlight in the scene have any affect on softening up the harsh lines? Or perhaps mess around with adding mental ray lights to those negative lights to soften them up? The lines might also not be as visible once you texture the wall and/or when you add the depth of field effect.

Nice scene, it will look cool once textures/shaders are applied.
Nice work

[jeremybirn]

Nice work!

The most controllable type of light to use with negative intensities is a volume light. It'll only darken what's within the volume, the volumes can be a lot of different shapes, and you get to edit a gradient from center to edge for the amount and color of its influence, so with the right scale and gradient you won't have too sudden a cut-off. Another big plus of volume lights as negatives is that you can set them to emit ambient, and turn off emit diffuse and emit specular. Since darkness doesn't really have a source or a direction, just sucking all of the light out of a volume without any negative hotspots can be much more gentle and natural looking.

In that particular scene, though, I don't know if you really need negative lights. There are other ways to fix light leaks in the corners of a set, and other ways to limit the spread of whatever lights were over-illuminating those corners. I try to save negative lights as an option of last resort, mostly because they are hard to render in isolation, and harder to split into layers or passes.

-jeremy

[xak0yax]

Nice work!

The most controllable type of light to use with negative intensities is a volume light. It'll only darken what's within the volume, the volumes can be a lot of different shapes, and you get to edit a gradient from center to edge for the amount and color of its influence, so with the right scale and gradient you won't have too sudden a cut-off. Another big plus of volume lights as negatives is that you can set them to emit ambient, and turn off emit diffuse and emit specular. Since darkness doesn't really have a source or a direction, just sucking all of the light out of a volume without any negative hotspots can be much more gentle and natural looking.

In that particular scene, though, I don't know if you really need negative lights. There are other ways to fix light leaks in the corners of a set, and other ways to limit the spread of whatever lights were over-illuminating those corners. I try to save negative lights as an option of last resort, mostly because they are hard to render in isolation, and harder to split into layers or passes.

-jeremy

I was curious about these other methods of fixing light leaking of corners. I'll definitely try the usage of volume lights, but I'm curious on other approaches. Thanks again!

[jeremybirn]

I was curious about these other methods of fixing light leaking of corners. I'll definitely try the usage of volume lights, but I'm curious on other approaches. Thanks again!

Check the geometry of the room, sometimes putting an extra primitive plane or cube just outside of the corner in question blocks whatever's leaking. It's best to build walls and foundations with a realistic thickness, but just adding an extra cube outside should prevent most leaks.

If fixing the geometry wasn't enough, then figure out which light(s) are responsible for the leak by hiding all your lights except for one at a time, and re-rendering that region of the image. You have to know which light to fix.

It sounds like you're using raytraced shadows, and you're not using any GI. Is that right? (If you were using shadow maps or photon maps there'd be different kinds of leaks...) If it's a raytraced shadow leaking, one reason could be if you're using a light radius to create a soft shadow, but the light is too close to the wall, so part of the "radius" being traced against extends inside of the room. If you're using a spot light with the MR area light option, then you don't also need any light radius in the Maya raytraced shadow options.

If you have any reflective surfaces in the room, make sure the ray depth limit is at least 2 on all your lights, otherwise shadows wouldn't appear in reflections and your reflections would go too bright in the shadow areas.

-jeremy

[xak0yax]

Check the geometry of the room, sometimes putting an extra primitive plane or cube just outside of the corner in question blocks whatever's leaking. It's best to build walls and foundations with a realistic thickness, but just adding an extra cube outside should prevent most leaks.

If fixing the geometry wasn't enough, then figure out which light(s) are responsible for the leak by hiding all your lights except for one at a time, and re-rendering that region of the image. You have to know which light to fix.

It sounds like you're using raytraced shadows, and you're not using any GI. Is that right? (If you were using shadow maps or photon maps there'd be different kinds of leaks...) If it's a raytraced shadow leaking, one reason could be if you're using a light radius to create a soft shadow, but the light is too close to the wall, so part of the "radius" being traced against extends inside of the room. If you're using a spot light with the MR area light option, then you don't also need any light radius in the Maya raytraced shadow options.

If you have any reflective surfaces in the room, make sure the ray depth limit is at least 2 on all your lights, otherwise shadows wouldn't appear in reflections and your reflections would go too bright in the shadow areas.

-jeremy

The voulme lights set to a negative value seem to be working pretty well for now...still got to make a few tweaks, thanks. As far as geometry, I didn't know that the lack of thickness or primitive would/can cause light leaks. And you're correct, I'm using raytraced shadows for my keylight (which is a spotlight), but also using a few depth map shadows in a few of my bounce lights (area lights). I don't think that any raytrace leak could be due my spot-keylight being too close to the wall...but its some insight I'll definitely look into. Great advice, appreciate every bit of it...will be sure to show the final render...THANKS!

[MAV4d]

i know if your using any type of gi or fg, the standard maya shaders will bleed like that. try using a mental ray shader... ie MIA_x or the mr lambert

should solve teh bleeding. Best of luck with negitive lights, ive never had them work correctly

[SanjayChand]

You could just fix that in comp, ie render out each light seperately and grad one/two of the lights affecting that area with a roto. Or just slap on an ambient occlussion and it would give a nice, but tighter, gradiation. lastly, you could also assign a surface shader to that wall, map a black/white ramp to the color channel to use as a matte to gain down/ gain up that area of the wall.

This is all with no negative lights.

[CHRiTTeR]

looks like tuning the gi strength can help you get the desired effect a lot easier ;)

[xak0yax]

well not really, a few tweaks here and there could be used, but this is what i got done in approx. 36- 40 hrs over a span of the last four days (had to get a full cgi scene for a portfolio submission) no GIs, no final gather, just spot-lights, area lights, ray-trace shadows, rendered in mental ray.

[Sorath]

hey man,
sorry but i like the first image more, the strong contrast and low-key situation does have a better mood in your scene. ..you almost lost the mood in the last image - maybe it's a bit better with depth of field!?
i know you worked hard on this, so just take it as my opinion.

cheers
Bastian

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