V Ray exterior scene

[Bret Bullough]

I have recently downloaded the free version of Vray. I am really excited about the photon mapping. Not to mention all of the killer images I've seen posted using the program. I've posted a scene which is my first attemt at using Vray. the over all light quality looks pretty good (although a little blown out)But I can't figure out how to get rid of the grainy look(softer shadows, smoother lighting greater detail). The help menu that comes with the free version is very limited.

 

and comments would be greatly apreciated.

 

TIA

[Bret Bullough]

Sorry-The Uplod utility didn't work the first time

 

http://www.cgarchitect.com/forum/filepush.asp?file=settings_5.jpg

 

http://www.cgarchitect.com/forum/filepush.asp?file=rendering_2.jpg

[Fran]

Hi Bret,

 

I don't know very much about Vray, but what happens if you increase your Sky samples for the Daylight Assembly?

[quizzy]

put your image sampling on addaptive subdivision

[Sawyer]

try yanking up the Hsph subs higher than it is at 50 and upping the number at the Subdivs to 4 (under AA next to fixed rate).

 

Personally I have gotten better results not using photon maps for the 2nd bounces and having direct comp. Thats just an idea.

[bguz]

I experienced a similar problem when playing with the free version and found that saving the image as a tiff (not jpg) made an amazing difference.

[Christopher Nichols]

First things first...

 

Your AA is set to fixed with 2 samples... not only will it be slow, but also grainy. Set it to adaptive with the default values. That sould be good for you.

 

Next you have way to much light in your scene. That is why it is washed out. You are using an IES sky... doen't really work that way for Vray. If you just want a skydome, do the following:

 

- place a light in your scene, any light, and turn it off. If you use no other lgiht, this is an easy way to turn off the daulft lights in MAX.

- go the the environment tab in vray and do an environment light overwrite, with the tint of choice. that is your skylight.

 

you are done.

 

other hints for you:

 

The method you are using is Irradiance mapping, not photon mapping. Photon mapping is only available in the professional version of Vray.

 

50 samples is an ENORMOUS amount of samples, since it is 50x50 or 2500 samples. Luckily Vray is very smart and highly adaptive about shooting samples so it never gets to shoot that many samples unless it absolutily has too. So don't change the samples, if anything go down to 16 or 20 for quicker tests.

 

Vray is not like radiosity so it does not follow the laws of IES... yet. So it doesn't work the same.

 

In terms of Vray shadows the default value is 8. Generally that is more then enough being as 8x8 is 64 samples. If you have a very large area shadow, you can go as high at 12 or even 16 but this will kill your rendering times.

 

Try these settings and lost your results if you want.

[Bret Bullough]

Chistopher, thanks for the detailed response. I tried your suggestions and the one that had solved the problem with resolution and graininess was the IES sky system I was using. I turned down the sampling and it really made a difference in rendering time.

 

I still have to tweak lighting but at least I'm now on the right track.

 

here is the latest image

 

http://www.cgarchitect.com/forum/filepush.asp?file=rendering-b.jpg

 

Here are the settings

 

http://www.cgarchitect.com/forum/filepush.asp?file=viz.jpg

 

 

It still has an AA problem. Do you have any suggestions for this setting, area, quadratic, sharp Q) too many choices.

 

Any other crtiques are welcome

 

thanks again.

[Christopher Nichols]

ok.. pretty good, from 15 mins to 1 min. that is what I call some good learning.

 

Ok as far as AA is concerned, you have it on Adaptive Subd which is good for most of what you do. If ever you have texture blurring you can turn your setting from 2,-1 to 2,0 or 2,1, or use Simple two level with 4,1 (default). That part is fine, but your rendering times will go up. I would try it on your scene. You will not see a difference, but you will see how much of a rendering hit that is.

 

Once it collect the samples to AA, it uses an filter to average them. That is what your AA filter is. They are the same is in regular MAX. You are using Sharp Quadratic, which I personally don't use, since it does not AA nicely as the others. The ones I use is Mitchell, for general smooth, cook variable for all around, and Catmul for sharp edges. Wait a moment... didn't Cook and Catmul write renderman? I think Mitchell did too... no wonder those are good AA filters.

[Bret Bullough]

I'll have to experiment with AA filters more. thnx for the tips.

Do you have any suggestions for illuminating the area behind the front collonade? I would like to show more detail in that area. Would you increase the secondary bounce value, or add aditional lighting to the scene(in terms of efficiency)?

Thanks for the feedback.

 

OUT!

[Christopher Nichols]

Well in terms of how you want the light to look you are in the more "artist" side of lighting... which is great, it means you have a better understanding of the tool and can now effect the image in a more personal way. The default secondary is set to .5 I think. That means that every time the light bounces the light is cut in half. That is about right. The reason you can't set it higer then 1 is because you don't want light to get more power as it bounces. For exteriors I never set my secondary higher then .7 and for interiors, never higher then .85

 

If you need more light give it more light with lights... try to increase the light level on the sun, without over-exposing it. If you want more light under the colonade do what photogaphers do and put a light there. I suggest a using a light with a high decay and slowly increasing the intensity until you get the desired effect. Depending on the size of your scene that intensity may be as high as 300 or even 1000.