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View Full Version : VRay SkyPortal - no 'shadows' (3ds max)


MrCroft
12-26-2010, 01:45 AM
Hi all...
Please help a newbie and excuse me for such basic stuff.
But before posting here I've looked through all the options I could find in max/vray and stumbled upon nothing that ringed any bells. And I've also searched google and these forums for related stuff and: nothing... no one I could find having this 'problem' and having posted about it anywhere.

I've just started to learn V-Ray and I came to a halt quite quickly.

I have a very simple scene to test the Daylight System and PhotonMapping GI.

So... I have the Daylight System with V-Ray Sun, Sky Environment - Enabled, and a V-Ray Light set as SkylightPortal (by the way, when I check the box "Skylight portal", some options become grayed out - like 'Cast shadows', 'Invisible', 'No decay', but I have them checked prior to checking "Skylight portal"... although I think it doesn't matter since they're grayed out, and anyway "Cast shadows" shouldn't have anything to do with lights of any kind, but only with actual objects that should cast shadows when hit by light rays... I know this much).

Here is my problem:
If I render the scene with Irradiance GI engine (I don't actually need the SkylightPortal) all looks fine :
http://www.cervitonline.ro/_images/CG_society/01-GI_Irradiance.jpg

The problem is when I use Photon Map as GI Engine. With the SkylightPortal - OFF :
http://www.cervitonline.ro/_images/CG_society/02-GI_PhotonMap_SkyPortal_OFF.jpg
the scene is extremely dark ofcourse (which is expected). And when rendering with SkylightPortal - ON :
http://www.cervitonline.ro/_images/CG_society/03-GI_PhotonMap_SkyPortal_ON.jpg
the scene is lit properly ofcourse (as you'd expect) BUT I get no shadows.
Why is that? In MentalRay I could quickly render a great quality simple-scene without much effort :
http://www.cervitonline.ro/_images/CG_society/04-Living_cam_02_AE.jpg
of course, this picture is also composited with AO and an AO edge pass which I overdid and has some color correction and materials are applied to the scene... don't criticize the environment, that I did not tweak, it looks tilted I know). And I only had like a week with mental ray.

In MentalRay it all comes natural, but in VRay on the other hand...
Can anyone tell me how can I fix this V-Ray issue of mine? I got stuck here :argh: , please help :wavey: .

P.S. In RT (Viewport-Active shade) it shows fine:

http://www.cervitonline.ro/_images/CG_society/05-RT_ActiveShade.jpg
(i don't know why it says "invisible enabled"... it was already checked by default).

Shadows and Generate/Recieve GI are checked/enabled anywhere I could find anything related: object properties (geometry, lights) and render setup.

MrCroft
12-26-2010, 08:29 AM
I think I found the "answer" (it's not actually an answer, but an explanation)... just correct me if it's wrong.

I'm also currently reading Francesco Legrenzi's "V-Ray The Complete Guide (second edition)" book.

In no example only one GI method is used, he always associates 2 methods.
Now, I know that in MentalRay I also use FG along with PM.

But in his book, PhotonMapping is nowhere among those recommended associations, neither for high-end quality (disregarding render time) neither for best quality/render time ratio. And for indoor static renders he doesn't even count it among the possibilities, as for indoor animation it is mentioned, but not recommended (because of artifacts).

I trusted PM, coming from MentalRay. Of course we trust what we already know. And naturally I was reluctant to use Irradiance, Light Cache or QMS (or Bruteforce in vray 2.xx.xx).
Is this true? What was the 'core' in mental ray GI (and achieved photo-realistic results) is just CRAP in V-Ray? I mean it makes me wonder "why is it still an option?" (sure, I'm not actually wondering that, it's just that I'm used to one solution that handled everything)...
In V-Ray, no matter what association I use, as long as I have PhotonMapping as primary, I don't get shadows (as long as I use a Skylight portal, which if I don't then the scene isn't properly lit). Is this the way things are meant to be in VRay (Photon Mapping doesn't generate shadows)? Leaving aside recommendations and quality etc. still, as crappy as the render quality might be, shouldn't I get shadows anyway? I mean indoors, with Photon Mapping as primary GI engine and using a skylight portal??

noouch
12-27-2010, 10:16 AM
Photon mapping is extremely scene scale dependent, and takes a lot of tweaking to get right in VRay. Most people I know don't even bother with it, and even the documentation doesn't speak very highly of it.

Also:

The photon map works only with V-Ray materials. Standard materials will receive GI, but will not generate any photons.


Irradiance map with brute force/QMC secondary bounces will probably work fairly well for 90% of your scenes. This is pretty much akin to using FG in Mental Ray. If you find yourself in need of a large amount of GI bounces, it might be good to switch to Light Cache for the secondary bounces. Brute force for both bounces also works very well, although it tends to be pretty slow. Also, the progressive path tracing light cache mode might be worth a look, although it's also very slow, and normally brute force produces cleaner results.

Really, GI in VRay is a topic you can spend a long time exploring. Best thing would probably be to look at the official documentation and the examples it shows:
http://www.spot3d.com/vray/help/150SP1/

thev
12-27-2010, 02:17 PM
Can anyone tell me how can I fix this V-Ray issue of mine? I got stuck here :argh: , please help :wavey: .Turn off the "Store direct light" option for the photon map and it will be fine. However, as pointed above, photon mapping is not the recommended GI method for V-Ray.

Best regards,
Vlado

MrCroft
12-27-2010, 06:21 PM
[...]
Also:
The photon map works only with V-Ray materials. Standard materials will receive GI, but will not generate any photons.
[...]

By "Standard Material" I suppose you mean "standard 3ds max materials" (non V-Ray specific), not the 'standard' VRayMtl/shader which you can build upon.
Of course I'm not going to use any material/shader to 'build' upon, unless it's a V-Ray mat/shader. And I don't see any point in ever doing that (using materials that aren't render-engine specific)... but I don't have a lot of experience anyway, maybe one would have a reason for doing that.

Thank you!

MrCroft
12-27-2010, 06:43 PM
Turn off the "Store direct light" option for the photon map and it will be fine. However, as pointed above, photon mapping is not the recommended GI method for V-Ray.

Best regards,
Vlado

Thanks for your answer, I can't believe I haven't tried that. I thought I've tried it, I had no doubt about it, but I decided to turn it off it 'again' after reading your post... and I got shadows. So the logic is simple "I only had the impression that I've tried turning that off, because I thought I've tried averything, but it's abviously I haven't".

Well, from the answers I got and from what I've read in the book so far, I guess it's bye-bye photon mapping while in V-Ray. It seems so primitive now. You have more options in V-Ray.

Sure, you can achieve photo-realistic results in any render-engine, it depends on the artist and how well one knows the render-engine options/abilities.

Thank you!

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