vRay -- Problems with windows

[Linsen]

Hi there,

I'm in the process of setting up a studio scene for the final renders of my Porsche 911 turbo. Unfortunately, I'm having some problems with the way my windows look. I attached two pics to illustrate this.

First one is a scene with an hdri for reflections and GI light and a vray light above the car. As you can see, the background when looking through the windows does not have any color and is too light. Obviously the hdri is showing through and not the background.

Second pic is a scene without hdri, just vRay default GI (white or light blue) and reflection/refraction checked to overrule Max settings. Other lighting is done with some planes which have vray light material on them. As you can see, the background when looking through the windows is very, very dark (please ignore the light area in the side window where indicated, that's just one of the light planes. I need to place it somewhere else). When I put the reflection/refraction environment to white (or any other color), what is seen through the window, changes to white (or any other color), obviously.

Additional info you might or might not need: The glass material is very simple vray material. diffuse=black, for reflect I tried about everything from white to dark grey. For refraction I also tried different values, generally I use pure white. In the options rollout I have tried everything from two-sided checked or unchecked, reflect on backside checked and unchecked, both checked, both unchecked etc., nothing helped.

In indirect illumination rollout in vray I usually have reflection and refraction checked, but I also tried with just refraction checked. Secondary bounces I usually set to 0.8 but I tried with 1.0 and dnothing really changed. The irradiance map settings (from very low to high) don't seem to have an effect on this.

Ok, I hope this is sufficient information for you renderings gurus to hopefully solve my problems. I mean, I sort of know, what causes it (the environment slot in the renderer), but there must be something to overcome this. From looking at other renders I know that nobody else seems to have this problem. I'm sure I must be missing something very simple and am just too stupid to notice.

Thx in advance,

Linsen

[steve123]

use opacity in the vray materials instead of refraction. Assign a falloff map to it so you can change how see through the windows are:)

[EquiNOX]

off issue...just helping with your render... if your light illuminate too high, you would need increase AA because I can see some grain on your car paint mats. However this would slow your render. Remember VRay hates GI which includes to multiplier of your HDRI, VRayLight or whatsoever related to GI.

Solution, add few lights, but make sure couple of them have low multiplier and use ONLY one light target with high multiplier which avoid slow render or some grains.

GL

[Linsen]

@steve123: Thx a lot, this has caused me soo many headaches, you wouldn't believe it. I can't wait to get home and try it out :).


@EquiNox: Thx for those suggestions, that'll be helpful and I'll keep it in mind.

But you're only talking about first renderer, aren't you? There carpaint is indeed way to grainy, but that would be mainly due to the low subdivs in the material settings (they were down to 8 or sth, tss). On the second one I set them to 30, and I think grain is gone, but there's of course also overall more light in the scene.

[yan]

which version of Vray you use?

@EquiNOX: "Remember VRay hates GI which includes to multiplier of your HDRI, VRayLight or whatsoever related to GI." ????

[EquiNOX]

But you're only talking about first renderer, aren't you? There carpaint is indeed way to grainy, but that would be mainly due to the low subdivs in the material settings (they were down to 8 or sth, tss). On the second one I set them to 30, and I think grain is gone, but there's of course also overall more light in the scene.

Well I am talking about second picture... Your first picture look okay but need AA, that goes for second picture too... but it also give grainy look.. you can see backround being burnt because of too much light intensity. The perspective of doing studio render is make sure lighting isn't too much except to one that is targeting to car which give some "glare of whole car" as for the rest keep it low so it can produce some reflection effects from your carpaint.

Its all in book where I've been studying on studio render. Not only that, it can make your render speed happy and neatness happy.

which version of Vray you use?

@EquiNOX: "Remember VRay hates GI which includes to multiplier of your HDRI, VRayLight or whatsoever related to GI." ????

VRay 1.5, I bought it a month ago... I got that statement from chaosgroup fourm.

[steve123]

@EquiNOX: "Remember VRay hates GI which includes to multiplier of your HDRI, VRayLight or whatsoever related to GI." ????

GI only starts to use up render time in interior scenes, most car scenes you can get away with using very low gi settings (atleast for testing)

Vraylight by defualt is direct light not gi so I dont understand that 2nd bit either.
Although you can add vray lights to irradiance map (gi) which actually speeds up the renders :buttrock:

[Ravens]

Isnt that to do with the standard envoirment color from max ? Press 8 .. and get rid of that black make it green.. Test it.. still black? Then im wrong :)

[Linsen]

@EquiNox: Erm, ok, in that case I think I don't quite understand what you're saying about "grain on your car paint mats". Car paint in second pic looks pretty smooth and clear to me. I agree however, that it could use a little more AA, but from my experience I don't think higher AA would noticeably reduce grain. I usually reduce grain by using a very low value in QMC sampler (I usually need 0.001) or by increasing subdivs in the material. Or, if shadows are grainy, I increase shadow subdivs in the vray shadow params. I also agree that the background in the second pic is too light in parts, or "burnt" as you say.

Overall, I'm a little confused now, as of course GI does make render times slower, I thought that was what EquiNox meant when saying "vray hates GI" (although vray is still pretty fast when compared to other renders and GI). And as stated by steve123, I usually do store my vray light with irradiance map and it really noticeably reduces render time (so does rendering the irradiance map from file).

Erm, well, overall I'm a little confused, I think, because I'm not sure what we're actually talking about ... :P

@Ravens: You're right, of course, if I change standard max environment color to green (or any other color) what is seen through the windows would also be green (or any other color). I think I said that in my first post, but that was just the problem: All I want to see through the windows is the background and not the environment color. Well, unfortunately I haven't tested what steve123 said, as I didn't have time yesterday, but I will do it today and hope that it helps.

I'll let you know :)

thx again,

Linsen