Camera flythrough with QMC

[mmrender]

Hello everybody,
I've just started to use VRAY and as you could imagine I have hundred of questions. But, to start with something, I have a doubt about flythrough animations. I went through the material that I found on the web, as the vray pages, Aversis or the forum itself. My question is how to apply the tutorial of flythrough animation using QMC for secondary bounces. I mean, should I calculate the irradiance map with secondary bounces turned off and activate it when render? Even, has any sense to use QMC engine for this kind of animations? What difference in quality would be between QMC and Light Cache?
I should say that I’m not using LC because it crash the render (but that’s other history, let’s concentrate in the questions).
Any help would be appreciated!
Thanks,
Manuel

[Morbid Angel]

this is a common question, you can search the forums Im sure there is many answers already. But to be brief, qmc is not a good idea to use in flythroughs. The whole point of irmap is to be able to precalculate some frames and not all, where as qmc has to do every frame from start, resulting in much longer render times. A good combination is irmap/lc. You are saying it crashes you machine? what vray/max are you on?

[mmrender]

Thanks for the answer. As you said, I'm still thinking in calculate the irmap every n frames, my doubt is more about the behavior of the saved irmap, that's it, if it save something from the QMC secondary bounce or not. I recon that it is a bit confused for me, if I understood well in the tutorial, the irmmap save also information of the LC secondary bounce, so at the end you only have to use first bounce to render the final animation.

Manuel

[s0real]

hi! welcome to the forum!

if you haven't seen it already, this tutorial for flythroughs with irrmap/lc is pretty good.

http://www.spot3d.com/vray/help/VRay...ials_imap2.htm

let us know how you get on.


:edit: forgot the link

[vlado]

Re: Camera flythrough with QMC

...My question is how to apply the tutorial of flythrough animation using QMC for secondary bounces....

In the same way as you would do if you use the light cache, but with these differences:

(*) Since there is no light cache, you go directly to the irradiance map rendering stage.
(*) Secondary bounces can be QMC both when you calculate the irradiance map and when you render. In theory, you can turn them off for the final rendering with a saved irradiance map, but even if they are on, they will not affect the rendering in any way - since the irradiance map is already calculated and loaded from disk.

Best regards,
Vlado

[mmrender]

Thanks for the help. I did a small test saving an irmap with and without QMC secondary bounce, this is what I found:

-irmap+QMC calculation took twice the time of irmap with no QMC (3min30sec vs 1min27sec). If I load those maps into irmapviewer you can see that the one with both first and second bounces is brighter than the other.
-Using irmap+QMC for render you get a better illuminated scene.
- As Vlado said, it doesn’t matter if secondary bounces is on or off for render time neither for the resulting image.
Render times:
irmap+QMC, secondary off, 19min21sec
irmap+QMC, secondary on, 19min29sec. Both images the same brighter illumination
irmap no QMC, secondary off, 19min07sec
irmap no QMC, secondary on, 19min03sec. Both images the same darker illumination

It looks like the loaded irmap override the secondary bounces effect.
If it’s not what you expected, let me know, maybe I did something wrong.

BTW, for Dmitry, I was looking to the showreel from your company and it looks fantastic. And in terms of flickering and image quality, just great. Is it done with VRAY? Could you disclosure some settings or it is “company’s secrets”? (my apologies in advance if it’s to much to ask).

Thanks,
Manuel

[studioDIM]

I rendered plenty of animations using irmap and qmc as secondary, with excellent results, very small rendertimes and memory occupancy.

Especially if your animation is long, both as number of frames and as area covered, using QMC can be many times smaller in memory than trying to do a good quality LC for the entire sequence.

Your crashes might indeed be due to a high level of LC subdivs, which would eat up all the available memory, and a bit...

just to throw in my 2 cents

Lele