IR/LC vs BF/LC...again...

[ben_hamburg]

Hi there,

I don´t do many projects with animations that need GI and for the last project (and after a lot of testing) I ended up with BF/LC.
I never touched the IR/LC combo ever since, until now.
Now I gotta do an interior animation and BF/LC just doesn´t give me he needed render times.
But since it´s been a while and a lot of the tutorials on the matter seem to be a bit outdated, I was wondering what the current workflow is.
In my scene I got camera animation and moving objects, so I went with the mintviz tutorial (you probably know the one).

On my first testings render times still were completely unacceptable (>40 min per frame).
After some more testing I noticed I still had IR Interpolation samples from animation prepass mode on 20. Once I lowered them to 12 (like it says in the tutorial), render times dropped to about about 10-15 min per frame.
But now I could already see that I would get into trouble with the animation, since I noticed some blotches on walls etc.
Of course I could now increase HSph. subdivs and LC (Irmap was set to "low" preset with 50 HSph subdivs and 20 interpolation samples fro the prepass), but since the moving object isn´t contributing much to the scene GI wise, I think we should rather render the room and the object in seperate layers, instead of increasing render times for every frame.
So here is what I would do:

1. Set up the scene so the moving object is set to "invisible to camera" and doesn´t generate nor receive GI.
2. Set IRmap and LC to "use camera path" and autosave each map.
3. Adjust HSph subdivs and LC settings so I get rid of the blotches (right now I´m testing with IRmap at medium (animation) preset with 150 HSph. subdivs and 20 interpolation samples, LC set to 1500).
4. Go to start of animation, check "Don´t render final animation" and render prepass for single frame.
5. Uncheck "Don´t render final animation", set both IRmap and LC to "from file" and render sequence.

For the object layer:

1. Make it visible to camera again and set it to generate and receive GI.
2. Make all other objects to Matte Objects with Alpha -1
3. Render prepass using "animation (prepass)" mode for IRmap and set LC to "single frame" (since I´ll be using it for glossy rays) and render prepass for the whole sequence +-2 Frames.
4. Render with "animation (Render) mode".
5. Comp both layers in post.

Since I don´t have much more time for testing, I´d love to here your advice on if I remember everything correctly or if I´m doing it wrong, or if there is anything else I need to check first to make sure I get blotches- and flicker-free animation...

[ben_hamburg]

Just a little follow-up to the overwhelming amount of responses...:

Yep, that did the trick.

[svetlozar.draganov]

Hi there,
1. Set up the scene so the moving object is set to "invisible to camera" and doesn´t generate nor receive GI.

If the moving objects are invisible to camera they will be visible in reflective/refractive objects and shadows, they will be darker since receive GI is off, they will most likely to flicker. It would be better to hide the moving objects instead making them invisible to camera - with this setup there is no need to exclude objects from the GI since GI calculation doesn't take into account hidden objects.

Hi there,
2. Set IRmap and LC to "use camera path" and autosave each map.

It is not possible to save out LC map for every frame. If autosave function is enabled the new LC map will always overwrite the old one.
The IM however will also bake LC map into itself - so you don't have to worry about the LC map at all.

Hi there,
4. Go to start of animation, check "Don´t render final animation" and render prepass for single frame.

There is no need to render IM and LC for each frame - you may render them at each 10, 20, 50, 100 and etc frame depending on speed of the animation. If the camera moves quickly you may set to render each 10th or 15th frame, for slow moving cameras you render each 50th or 100th frame.

Hi there,
5. Uncheck "Don´t render final animation", set both IRmap and LC to "from file" and render sequence.

There is no need to load LC from file - you may actually disable secondary GI engine completely. When IM is set as first bounce engine it always stores the information for the secondary bounce engine into itself.

Hi there,
2. Make all other objects to Matte Objects with Alpha -1

By default No GI on other mattes option is activated in Matte Properties - this will make the GI on the moving objects darker since the GI won't bounce between the different mattes.

For the fly-through part of the animation please check this tutorial - http://docs.chaosgroup.com/display/V...ough+Animation
For the moving-objects part of the animation check this one - http://docs.chaosgroup.com/display/V...ing+Objects+II


There are two more approaches to render such animation, the first one is to use VraySphereFade feature which is described here:
http://docs.chaosgroup.com/display/V...Moving+Objects

... and the second one is to use a combination of IM+LC for the static objects in the scene and BF for the animated objects. We don't have official tutorial for this approach, let me know if you would like to know more about it.