Rendering an animation with moving objects

[vlado]

There's one thing I don't understand though -- if the VraysphereFade thing creates a 0 alpha (does it?) for the grey surroundings, why can't you just superimpose (with a normal blend mode) the 'sphered' layer with the character and immediate surroundings directly over the backdrop?

Well, the VRaySphereFade plugin generates white alpha for the grey cut-off parts, which is the first problem. Even if it did generate black alpha, using it would mean replacing the entire background with the rendering inside the sphere, which is not what we want - we would like to keep as much of the original background as possible, introducing only the changes that are really necessary. This is why we need the "black" and "pure" renders - to isolate only the differences that must be made to the background.

Best regards,
Vlado

[davision]

Even if it did generate black alpha, using it would mean replacing the entire background with the rendering inside the sphere, which is not what we want

Well, this is where I don't understand. Since the Vraysphere normal layer is still using the same background (with the addition of the animated objects), why shouldn't we replace the main backdrop with the slightly altered backdrop in the sphere?

What is the disadvantage of doing it in this way?

[plastic_]

it's not a firefox problem.
vlado, your webserver is wrongly configured...
i guess the MIME types for PNG and AVI are not set correctly.

[vlado]

Well, this is where I don't understand. Since the Vraysphere normal layer is still using the same background (with the addition of the animated objects), why shouldn't we replace the main backdrop with the slightly altered backdrop in the sphere?

This would be true if you use the same scene for the background; but it will not work if you have to composite the result over a quite different background (for example, live footage).

Best regards,
Vlado

[dbuchhofer]

Well, this is where I don't understand. Since the Vraysphere normal layer is still using the same background (with the addition of the animated objects), why shouldn't we replace the main backdrop with the slightly altered backdrop in the sphere?

Because theoretically, you rendered the 'pure background pass' with a saved or static lighting solution, and the animation portion that you cut out using the sphere with a single frame dynamic lighting solution, so the parts of the 'background' plate that come through in the animated single frame portion, will not match exactly the lighting in the static lighting solution. which is why you use the black pass as your mask for what to use out of the animated pass.

using the black pass will let you pull the reflections out of the animated plate, but how do you bring in the GI shadowing that would go along with the animated object? I'm not sure how you would do this even in a normal matte pass.

[davision]

This would be true if you use the same scene for the background; but it will not work if you have to composite the result over a quite different background (for example, live footage).

Aha, now we're getting somewhere. Yes, I understand that if I was using live footage that the straight composite I mentioned would be useless, however I imagine a lot of folks (like myself) would like to use this vraysphere to accelerate animation renders for a completely 3d scene.

so the parts of the 'background' plate that come through in the animated single frame portion, will not match exactly the lighting in the static lighting solution.

And Dave, it seems the problem you mention could be alleviated (or minimized) in one of two ways. One solution would be to use very similar (or identical) settings for the background pass and the animation pass.

The other solution, which is superior, would be to make sure the vray sphere layer is heavily feathered so that any lighting shifts in the animated plate would be blended away as it transitions to the background plate. The vraysphere renders are naturally feathered right? Is this level of feathering adjustable?

Also, Vlado -- can you make an switch that forces the vraysphere's surroundings to have an alpha of 0 so I can use it for simple composites on my entirely 3D (non-live composite) scenes???

One more question -- when comparing my preferred method (i.e., normal simple comp -- rather than the 3 pass version you described in the tut), versus the old-fashioned method of using a matte/shadow material, which is faster from a rendertime standpoint?

Oh, and thanks for all the feedback Vlado & Dave.

[flipside]

Vlado, even when logged in, I can't acces this tutorial. Also it is not listed under the tutorials section in the help file.

When I first click another tutorial, and then change the url to tutorial_anim.htm at the back, I can acces it.

[corey]

I think that link is still not the same page as before...it's missing the final part.

Vlado, can the link be reconnected?

[gilicom]

can't see that tuttorial
when i press the link i go to the main chaos page
and when i save target as it also open the same page
and yes i did log in before.

[flipside]

I have the same problem.

When I login, go to the help docs, click another tutorial and then change the last part of the url to 'tutorial_anim.htm' i can see it...

[rfellers]

Just browsing through old posts looking for info on rendering moving characters with vray - is this tut still available? After I login the link takes me to the vray 'private section' with no tutorials. Can I get this tutorial or has someone created an updated version that I could get?

[flipside]

Here it is:

http://www.spot3d.com/vray/help/VRay...rials_anim.htm

[rfellers]

Thanx flipside. The results are far better than anything I ever acheived w/ matte material.