Light Cache in interior animations

[edgar_cg]

Hi,

I am rendering interiors and so far I have only accomplished something well illuminated with a combination of IM and LC. Since I have to render a sequence of 200 frames, and the building of the Light Cache is taking too long, I am wondering if there is something similar to the Incremental Save in IM. I believe it is the case for the option called Fly through in LC. I guess that I have to make the passes while I do the passes of IM and save a final LC map at the end.

Is that correct?

Thanks for the help

Edgar

[Micha_cg]

Re: Light Cache in interior animations

No idea here, but I needed the LC for speed up the glossy reflections often too. So, a blury reflection wood ground and you lost much time without the "use for glossy rays" option.

[dalomar_cg]

Re: Light Cache in interior animations

Yes the Fly Through mode for LC is essentially the equivalent of Incremental Add (although they work VERY differently, so thats basically where the comparison ends). Unfortunately, this isn't working in Rhino right now...and, when it does work it will only work with Bongo, not Rhino's built in animation tools, so if you're using those it won't matter any way.

The reason why FlyThrough mode won't work is because it doesn't work frame by frame as incremental add does, but it actually samples the whole camera path at a given time. This means it needs access to that whole path, which isn't set up right now (will require some bongo trickery from Joe). The other thing is that there are no ways to merge LC maps like you can IM, so doing one LC calc every so often as is done with IM can't be done.

Right now, for animations at least, I would ditch LC for secondaries and just use QMC. You may need to manage the amount of bounces (3 is the default, but typically not the best for interiors) along with the secondary bounce multiplier (you can "fake" extra bounces by increasing the secondary bounce multiplier higher then 1...this is of course not physically correct, but may be effective).

[Micha_cg]

Re: Light Cache in interior animations

... The other thing is that there are no ways to merge LC maps like you can IM, so doing one LC calc every so often as is done with IM can't be done.

Could you ask Vlado to implement this feature? I suppose so, he don't implement this feature, because 3dsmax don't need yet. But for the plugins it could be a help. Not so perfect like the 3dsmax direct flythrough calculation, but better than nothing.

[edgar_cg]

Re: Light Cache in interior animations

The problem for me in this case of using QMC for second bounces, is that it does not bring enough light to the scene. In that case, I would have to bring more lights, and my rendering time would increase (already 5min/frame). Then doing an animation would be impossible.
Any suggestions?

Thanks
Edgar

[Micha_cg]

Re: Light Cache in interior animations

My question is: is an image rendered per QMC+IM faster than LC+IM? My test here show me:

LC+IM - 3m56s
QMC+IM - 8m58s (3 bounce)
QMC+Im - 5m4s (1 bounce)

The test scene is a caravan interior with opening at the ceiling and many windows (easy GI case) rendered at 360°. The QMC lighting looks quite dark. The combination LC+IM create a perfect image.
The LC speed up the IM calculation and the calculation of blury reflections. Maybe my test is not the best, but it show, that LC+IM seems to be not so bad.

Could you show some images of the scene? Could be helpful to improve the speed.

EDIT: one test more with low GI settings: single IM pass max rate -1 and 80 subdivs and 20 samples and LC 500/0.05 (prefilter 50 + interp samples 20) -> 2m48s. This is a question of the quality and the shadow details here. The same low IM setting but with QMC -> 3m4s and low bounce lighting look.

[dalomar_cg]

Re: Light Cache in interior animations

In the Indirect Illumination rollout next to where you specify the engine is a multiplier. Try increasing that multiplier till you get suitable results. There are a few other tweeks that you can do, but I'll have to take a first hand look at your scene to advise you on those.

[dalomar_cg]

Re: Light Cache in interior animations

Could you ask Vlado to implement this feature? I suppose so, he don't implement this feature, because 3dsmax don't need yet. But for the plugins it could be a help. Not so perfect like the 3dsmax direct flythrough calculation, but better than nothing.

As far as I understand LC maps cannot be merged due to the process in which they are calculated. Basically each LC sample has rays traced from the camera, then bounced around the scene. So if I change the point of the camera, the rays that went into calculating the result for that same sample will be different. With IM this is different because, although the placement of each sample is based on camera location, the actual calculation of the illumination of that sample is the same every single time (subdividing a hemisphere). So this continuity between how each sample is processed is what allows IM to be merged.

[Micha_cg]

Re: Light Cache in interior animations

Did you mean, a sampled point at the room show not the same brightness from different camera views?

My theory is, that the incremental calculation waste render time compared to the flythrough, because some areas are several calculated. If the rays are send from a flythrough line instead a point, than the samples are shot more homogeneous along the camera way through the room. I hoped, Vlado implement the flytrough, because 3dsmax support it and it's more efficient than incremental save.

An other question: if "flythrough" could be implemented for bongo, could it be implemented for the Rhino animation tool too? For example, a Vray UI ask the user for the path curve of the flythrough animation?

[dalomar_cg]

Re: Light Cache in interior animations

Did you mean, a sampled point at the room show not the same brightness from different camera views?

The brightness should end up being the same (depending on how accurately it is sampled)...however the raycasting structure that generated that brightness will be different for each position of the camera.

My theory is, that the incremental calculation waste render time compared to the flythrough, because some areas are several calculated.

There is no incremental option for LC, so you can't add to existing LC samples. What exactly are you referring too?

If the rays are send from a flythrough line instead a point, than the samples are shot more homogeneous along the camera way through the room.

Thats not how it works...LC in flythrough mode samples the whole camera path. This means that a give sample (a static area of the scene) has rays that are traced from a bunch of different places along the path. Because we can't reaccess that LC sample to add to it, this process has to be done simultaneously. So that means when doing an LC calc in flythrough mode is very different from doing a single frame LC calc or an Incremental Add IM calc. There is only one "frame" and the preview is essentially unrecongnizable. The samples themselves are actually distributed across the whole path, not just for an individual "frame". I know this is wierd, but if you look at the LC pass you'd know what I mean...here it is

An other question: if "flythrough" could be implemented for bongo, could it be implemented for the Rhino animation tool too? For example, a Vray UI ask the user for the path curve of the flythrough animation?

Not through the current Rhino UI. Yes, through a piece of V-ray UI it could, but then there is no way to make sure that it will be the same for the V-ray calc and the rhino animation (i.e. their isn't a way to check, so there could be user error that could lead to differences between the two)

BTW rhino support of LC flythrough is not Vlado's issue its ours (we have it working in SU if I remember correctly)

[Micha_cg]

Re: Light Cache in interior animations

The brightness should end up being the same (depending on how accurately it is sampled)...however the raycasting structure that generated that brightness will be different for each position of the camera.

In my mind is the Imap viewer that show the sample brightness of the 3D scene. So, per LC we know the brightness of surfaces points at the scene, so why not merge the results from different views? But, if you say it's not possible, than it's good, I must confess, I don't understand to much about the theory behind.

There is no incremental option for LC, so you can't add to existing LC samples. What exactly are you referring too?

I mean, if incremental mode could work for LC too, than flythrough is a better method than incremental. Per incremental method calculated areas would be overlapping and per flythrough not.

Yes, through a piece of V-ray UI it could, but then there is no way to make sure that it will be the same for the V-ray calc and the rhino animation (i.e. their isn't a way to check, so there could be user error that could lead to differences between the two)

So, the user could be ask "select the animation path" and VfR could use it? You mean, the problem is, if the user select the wrong path, than the result looks wrong? I would say, that's life. But it could be great, to use the Rhino animation tools for simple turntable/flythroughs. I would not buy Bomgo for turntables only. (I own bongo, so my wish for a turntable support isn't for me.)
Or Joe implement it for careful users as hidden test command - _testvispath.

[dalomar_cg]

Re: Light Cache in interior animations

Well in thinking about it a little more, there is another issue. With IM the information is just points that are infinitely small and at render time those points are reconstructed. With LC, each sample is a given size, or area, in space, so if you tried to merge different passes you would have samples on top of each other, and thats why you would need the raycasting structure to sort the two out. But as I already said, the raycasting structure will be different from 2 camera points, so it would be very hard to merge them.

As far as the animation path thing, I guess that is life. Although for turntables it should be easier then for path animations.

[edgar_cg]

Re: Light Cache in interior animations

Is there an IMap viewer for VRay for Rhino? That would be very helpful

[dalomar_cg]

Re: Light Cache in interior animations

Go to Downloads>My Files>Tools...thats where it should be. If it isn't then send Joe an email and he should be able to set you up with it.

[Micha_cg]

Re: Light Cache in interior animations

Thanks Damien, I'm curious for the flythrough support.