Thursday, 4 November 2010

Getting quality renders with vray

Okay so I'm going to take some time to explain Anti Aliasing, its one of the core elements you need to set up before you start any render you plan on doing. The render engine i use is vray so I'm going to talk about some of different methods you can use and some of the  pro's and con's that come with using them.
First a little explanation about AA.
AA is a technique in computer technology that  minimizes the distortion artifacts known as aliasing.
 As you can see in the image above, the jagged form in the top pic  is a consequence of  no AA being computed onto the line, the image being pixelated  gives of a sharp look and most of the quality is lost when zoomed in or scaled up.
Onto the bottom pic AA is applied , in 3d software the render engine fires out samples to determine how to color the pixels around the line, effectively faking a smooth look.
When viewed from a distance i think all would agree that the bottom example looks more attractive.

Now about setting up your render with vray. I myself use vray for maya and am presented with 3 different types of AA, but this may vary for different apps.These are the 3 methods you can use.
-Fixed
-Adaptive DMC
-Adaptive subdivision
What i will state now are some guidelines i like to abide to, but they are not a strict set of rules, and rearly apply to every scene your working on. More or less they should be a starting point from which you should start tweaking to get the best quality vs speed results.

The fixed sampler rate should be used for scenes that have over 75% of the image in high detailed areas. Because the fixed sampler always takes the same number of samples per region it renders.
I prefer to start of with a 1 subd  sample rate for test renders and 3-6 for production renders.

the Adaptive DMC takes a variable number of samples per pixel depending on the difference in the intensity of the pixels. So it should be used for scenes that have less than 75% of high details in the image.
Some values i like to use are 1/4 for test renders and 3/6 for productions renders

And finally the Adaptive subdivision method. This sampler divides the image into an adaptive grid-like structure and refines depending on the difference in pixel intensity. So this method should be used for images with a large amount of flat surfaces. Values i use here range from -1/2 for test renders and 2/5 for production renders.

Here is a small preview. Its a hand i did some time ago, the left side is rendered with an Adaptive DMC method with a sample setting of -3/0 and the right side with the fixed method and a total of 3 subdivs per render region. The left side rendered relatively quickly whilst the right side took a descent amount of time.


Again these values are not a strict guide line and most of the time you will have to play around to get good render times but they really are a good starting point. If  anyone does any renders i hope this help you out if you were having any trouble before. Thanks for reading :)

48 comments:

  1. Very nice read, the hand looks amazing!

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  2. Thanks and nice read even tho i never plan on doing this

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  3. Very informative mate, Can't wait to read more!

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  4. I love your blog! Following! ^^

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  5. I wonder what V-Ray would look like in games!

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  6. Dude, you are actually really good at this.

    +1

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  7. wow, always wondered what was this anti-aliasing thing for, now i finally know, thanks man. also; great post.

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  8. you are too good at what you do. keep it up!

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  9. you're pretty sick on the CAD type stuff

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  10. Wow...this is actually something I was kinda wondering about but didn't actually go and look up. Thank you for answering my question before I ask it.

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  11. 1st picture cleared that up.

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  12. Hmm that was good info. But what does 4x AA vs 8x AA mean?

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  13. Podrska za brata :) . Very informative btw

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  14. Damn you AA! Always making my graphics card work so hard :(

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  15. Very helpful, I now actually understand, thanks.

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  16. The best part about getting a new video card is being able to turn max AA on in all your games. Makes it look amazing.

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  17. Oh, now is more clear, I rather anti-aliased

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  18. OOOOhhhh, that's what anti aliasing does

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  19. Kewl story, bra! waiting for updates from you

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