Illumination Data

[RayOfLight]

A new thread for a new thought..

Is it possible to store the lighting data in the raw-file, seperated per lightsource?
So you can change the intensity of a lightsource after rendering, much like the maxwell multilight option?

[Neilg]

Vlado has already said in the past this isnt possible with the current irradiance map/light cache options. I think its just a limitation of it being a biased renderer - weather its just the GI holding it up or some major parts of vray making it not possible I dont know, but it'd be a hell of a lot of work to implement either way.

[RayOfLight]

ah, I expect it to be a lot of work, but it's just a theory.
I don't know how lighting information is handled.
What does happen when Light Cache works the scene...how does it get the data, and what does it do with it...and the same for the irrandiance map...

Perhaps I should start to have some fun with the SDK too

[vlado]

This is possible to be done for the direct lighting component as it is easy to separate out the different lights. For the indirect light however, this is more complicated as the light cache/irradiance map samples store contribution from all lights of the scene in the same samples and it is not possible to separate this without increasing memory requirements and render times. For an unbiased renderer where the results are not cached and reused in any way, per-light separation is easier (e.g. it can be relatively easily added to the path tracing mode of the light cache).

Best regards,
Vlado

[RayOfLight]

and you're still coding on the progressive path tracing mode right?
Might be a future possibility, users can choose fast and nice, or a bit slower and more options.
They will use the fast settings (Irradiance map and light cache) for animations and ppt for scenes where they want to show different lighting studies...a nice addition to the new versions of 3dstudio...

[Aldaryn]

If you can live with "slow but more settings", render out a sequence of images of your scene, each time with only one lightsource (or group them as you wish. ) turned on, save as hdr, and composite it later in post. Even PS can do this pretty well (now that hdr layers are supported). This way, you can tweak every light layer separately.

Problem with this, is that you have to render everything multiple times. AA, reflections, all the sample hungry this, but with some smart tweaking you can get really good results both in output, and rendertime. For example, if you use only per pixel methods, and stay away from interpolation on problematic areas (to avoid high contrast splotches) you can render each light setup with fewer samples. The combined images will behave just like if you've used more samples, noise will go away with each layer overlayed. (adding another layer works just like adding more samples, and note, for this to work, you have to render each frame light pass with a different noise seed)

So, it's not that hard to "implement" this, even scriptable, since all you need to check and switch are easily accessible light sources, and specific (self illuminated) shaders.

Best regards,

A.

(edit.: just to add, if you use the dmc aa to handle all the sampling, it's quite easy to calculate, and handle how much you need to degrade the separate passes to end up with the desired sampling quality)

[percydaman]

I have done this before. Using a program like rpmanager, you can set this thing up pretty easily, so that you don't burn yourself out after the first time sending out all your passes.

[Dschaga]

So, it's not that hard to "implement" this, even scriptable, since all you need to check and switch are easily accessible light sources, and specific (self illuminated) shaders.

 
for a in $* where (superclassof a == Light)  do a.enabled =off  -- switch off all lights

for b in $* where (superclassof b == Light)  do 
(
	b.enabled = on  -- switch on
		
	--render the image with only one light
	render vfb:on channels:#(#RAW Lightning, #Diffuse filter) --outputFile:(b.name + ".png") 

	b.enabled = off	-- switch off
)

the question is if it makes sense to only render the RAW lightpass and the Diffuse Filter pass and composite them without reflections and refractions ...just like the "don't render the final ..." rendersetting

[RayOfLight]

the idea is to make this possible in the VFB, because it's easy to work there.
Colormapping can also be done in both PS and VFB...and I use the VFB because otherwise I have to start up a whole different application..
And with the current increasing amount of single and multi quadcores with loads of RAM, working in 64-bits, using more memory will be less and less an issue..

[Aldaryn]

[code]
the question is if it makes sense to only render the RAW lightpass and the Diffuse Filter pass and composite them without reflections and refractions ...just like the "don't render the final ..." rendersetting

I think not, you would need a separate pass for each light group for every reflection/refraction etc, you can't just render out those in one go. But I think the point is that you can do this, and pretty simply right now.

Anyway, some support from rendering application is always welcome.

Best regards,

A.

[Dschaga]

that's why i was asking.. maybe we could think about something like the standard camera multi pass effects? If you have 5 lights the samplingquality would be 1/5 for each render/light pass, which will give you for the final image the desired sampling quality and the summ of all lights ..but you could still render for each light a RAW lightchannel ...