Light Intensity Spacewarp

[soulburn3d]

Many times you need to tweak the intensity of a light in a specific volume in your scene. Reducing the intensity of the light itself can solve the problem, but it will also affect other areas of your scene that you may not want to affect.

I'd like to see a spacewarp that defines a volume that would affect the intensity of a light. Like lets say you have a character who's nose is too bright, but you like the brightness on the mouth area and cheek.



You first add one of these spacewarps to the scene. Change the Intensity to 0.5 (it should be able to brighten or darken, so 1 is neutral, below 1 is darker and above 1 is brighter). It also has an Inner and Outer Radius. The Inner Radius defines the full 0.5 intensity multiplier. The outer radius is no effect, with a smooth gradation in between the two radiuses. This is so you don't get sharp edges where the Gizmo affects the light.



Now move the spacewarp into position...



If your character animates, you can animate the position of the spacewarp to follow the nose, or you can attach it to the nose using linked xform or another feature.

Now bind the spacewarp to the light that's causing the extra brightness.

And now that light isn't as bright, only on the character's nose.



- Neil

[joconnell]

Hmm - it's kind of like the pworld pass being used in comp - it's a position pass but instead of everything used in world space, you can set an object to use as the center of the world that all the coordinates spread out from. This pass can be used to make mattes in nuke that'll lock to your object so as you want, it'll travel with your characters nose or whatever you've chosen as the reference.

It's not quite in the render, but the option's there to do it in 2d after.

[Rens]

Nice idea! Alternatively you could do something similar material based:

- Place your material as the base in a VrayBlendMtl.
- Place a fully black (V-Ray) material as the first coat.
- Set the Blend Amount colour to black.
- Create a helper object, place it where you want the material to be darker.
- Create a Falloff map as the Blend Amount map.
- Set the falloff to Distance Blend / Object.
- Pick the helper object.
- Adjust the distances and the Distance Blend percentage.

Now, this will darker your whole material, including all reflections and there's no light select. You could also multiply the Falloff map with just the Diffuse colour using a VrayCompTex set to multiply, essentially lowering just the lighting, not the reflections and speculars.

[super gnu]

to be honest i dont know if vray supports it, but we used to do this with lights with a negative multiplier back in the scanline days. you could use them to "suck" light out of an area.

[vlado]

to be honest i dont know if vray supports it, but we used to do this with lights with a negative multiplier back in the scanline days. you could use them to "suck" light out of an area.

No, we don't support this, it's a terrible idea for a physically based renderer.

Best regards,
Vlado

[vlado]

Neil, I can't see any images in your post...

I know that renderers like RenderMan and Arnold have this capability, and it has been requested half-heartedly a couple times for V-Ray - but overall it seems that users can get the job done in other ways. I'm a bit hesitant to implement this, as it makes things more complicated.

Best regards,
Vlado

[super gnu]

i might start a fire here, but ive never considered vray "physically based" its only since the advent of the physical camera that we are heading towards that as an ability at all. .. ive always just considered it a renderer, with physically based options, and also non-accurate ones.. since you can always put silly numbers in any setting.

for me the physically accurate side of things is nice to get something looking good without too much guesswork, but id also prefer not to have it as a limitation.. i.e. "we cant do that, its not physically accurate".. renders are not always of the real world. (and this is coming from someone who does arch vis... )


of coursde all this represents just my personal opinion.. love vray to bits, but to limit it to reality, seems, well, limiting.

[vlado]

for me the physically accurate side of things is nice to get something looking good without too much guesswork, but id also prefer not to have it as a limitation.. i.e. "we cant do that, its not physically accurate".. renders are not always of the real world. (and this is coming from someone who does arch vis... ) of coursde all this represents just my personal opinion.. love vray to bits, but to limit it to reality, seems, well, limiting.

Hm, not sure what that has to do with the thread. I said it makes the code more complicated to support; I can totally understand why people might need this from a practical standpoint. We will do it if it's a must, but I need convincing that this is the case - it's a lot of work to implement a very specialized feature that is not quite directly related to rendering (there's lots of UI coding involved) that will be used in a limited set of circumstances. So it must be a justified effort compared to all other things on the list.

Best regards,
Vlado

[super gnu]

oh please dont get me wrong, i wasnt complaining its not supported, or even asking for it.. you guys have got a to do list longer than the library of congress.

ive not used that trick (or missed it) since the scanline days. it just seems i misinterpreted your "its a terrible idea for a physically based renderer" to mean that you didnt think that kind of trick has a place in a renderer such as vray, when in the end, rendering is all about tricks. hence my reply.

[soulburn3d]

Hey Vlado. My websever went down last night, the images should be back up. Yes, there are other ways to achieve this, but none as simple to use from a user perspective IMO. I don't use the negative light trick since there's the real possibility of achieving an area of "negative light", which will cause the lighting and textures to look completely messed up. So this would instead just be a multiplier on the current existing light. I certainly would use this feature all the time, if you need convincing that enough people want it, I guess the only way is for the users to add their voices, everyone reading this thread, if this would be useful to you and you'd use it more than just once in a blue moon, please post your use cases!

- Neil

[samuel_bubat]

A solution to achive something similar with current features would be a Vray distance tex that blends two maps or shaders. It doesn´t support gizmos but any object (just untick renderable).
Putting a Distance tex into an output map let´s you control precisely the fallof curve. Of course it´s not exactly the same and will result in higher rendertimes,
but it also has advantages like beeing able to additional control things like reflections and basically each aspect of a shader. Also you can use more complex objects than a sphere, box or cylinder.
Regarding this special problem about parts beeing to bright. I ´m doing a lot of product vis. And I often have to fight highlights that look good in one perspective but to bright in another.
I usually come around this with a low burn rate from the reinhard tone mapping.

[bigbossfr]

Neil, I can't see any images in your post...

I know that renderers like RenderMan and Arnold have this capability, and it has been requested half-heartedly a couple times for V-Ray - but overall it seems that users can get the job done in other ways. I'm a bit hesitant to implement this, as it makes things more complicated.

Best regards,
Vlado

Maya user here but, what do you thing about to add the user attributes stuff with light ?
For example, i have a light intensity 2. I add an user attribute into an object with a value of 1. This object will get a light intensity of 1.

Ok, this is "by object" but this is better than duplicate a light and do light linking.