Raytrace Settings

[Chris Wolf]

Here are some settings that i use to speed up the raytrace material, and make it look a lot better.
these settings are found in the
Raytracer controls....Global Parameters and Options.

The raytracer has been setup with default settings that work in most scenes without a hitch, but optimizing the settings can make a huge difference if you have an out of the ordinary scene...like one with lots of geometry.

For starters, before i render anything i go to....Raytracer controls...options.....
and set the antialiasing to be off.
the reason for this, is that the tracer antialiases with a lot of extra rays, that take a long time to compute.

but...how do i get rid of the jaggies you ask?
well...instead of antialiasing using the raytracer, i use the supersample button instead(Raytrace basic parameters)
since this uses an image based antialiasing technique, it is much faster for complex scenes.

Since you dont want to test render every scene using supersampling, turn it off globally in your rendering dialog box, and switch it back on when your about to do a final render.

btw...i use supersampling on almost all textures, due to the fact that max is set up for blazing speeds, not image quality.
so it antialiases only the edges of objects.
Have you ever noticed crawling textures in your animations? just hit the supersample button...and its gone.

Now onto the raytrace settings....
For small scenes, the raytracing settings are fine, dont even bother touching them.
But if you have a scene with 1 million polys or more, the raytracer slows down to a crawl.

This is where you should launch the Global Parameters.
And switch to Manual Acceleration.
and set your face limit slightly larger than the poly count of your biggest object in your scene (like trees)

My scene weighing in at 2.4 million polys was rendering at 5.40 mins,
after i set the face limit to 10,000 (my trees were 8,500 polys each)
i got the rendering time down to 3.50 mins
with the big improvement in speed, at the raytrace engine setup stage.

Another thing to keep an eye on, is the raytrace depth, which is on 9 as default.
great for doing a glass statue, with lots of rays shooting in and out of the statue,
but i find your basic architecture scene uses no more than 2-3
If in doubt about what depth will be enough,
next to the raytrace depth is a button that you can set a colour to use at max depth, if you set this colour to be bright red for instance, and render your scene, just look out for any bright red areas where your ray has died and used that colour instead.
and then if u see any, slowly up your raytrace depth untill the red is gone.

Hope this helps a few of you, as the default settings are meant for simple scenes, not complex architecture, such as what we do.

Wolf

[Héctor Corcín]

thank you for sharing this tips... Yes. It's very important to use the supersampling and not the antialiaser. the problem is when you want to make a blur reflection (ie. some metals...) then you have to activate the multiresolution antialiasing.

I also uncheck the following options in the raytraced material that are not useful for architectural models:

Enable Self reflect/refract (it depends of how is it modeled of course)
Render objects inside raytraced objects
Render atmospherics inside raytraced objects

[Evert Vandenberghe]

Tnx Wolf

[juanco]

Wolf: thanks a lot man!!!...finally I will be able to try some raytracy on my works...till now it was a taboo for my computer...lol
take care..
thanks again

enoone.

[Evert Vandenberghe]

Hi lads,

Anyone knows other tricks to speed up raytracing?


nisus

[Chris Wolf]

Have you tried Vray?
apart from an excellent GI renderer,
it also Rips through high geometry count raytracing

[Evert Vandenberghe]

mmm... gonna try that baby ,

nisus

[Jesse Sandifer]

I've also found that in the raytraced shadows parameters of max you can change the max quadtree depth from default of 7 to a max of 10 and it really shortens the time to render. 1 is the slowest and 10 is the quickest. I'm still experimenting with this parameter and haven't really seen any shadow quality changes yet.

[Evert Vandenberghe]

Hi sandpiper,

I had a hard time believing this as the manual states "Max Quadtree Depth: Adjusts the depth of the tree used by the raytracer. The greater this value, the more accurate the shadows but the longer they take to render. Default=7.".

I tested it myself and got these rendering times:
Max Quadtree = 7 : 5min59sec
Max Quadtree = 10: 1hour5min42sec

rgds

nisus

[Jesse Sandifer]

hi nisus,

thanks for the reply. Assuming you are using 3dsmax 4.26, this should work the way I described. I had an image taking up to one hour and it is now rendering in less than ten minutes. If you have the manual, check out v2-p.453 and also v3-p.647 to see what it says there: "Greater quadtree depth values can improve raytracing time at the cost of memory use. However, there is a depth value where the performance improvement is offset by the time it takes to generate the quadtree itself. This depends on the geometry of the scene. Default=7."

Be sure watch it with the omni lights because they generate up to six quadtrees and take much longer than spot or direct lights.

Maybe it's a memory issue. I don't know. All I know is that it worked for my problem and I thought I would help others by relaying this info on. It may be a lot more picky about geometry and types of light than I thought. I think it depends on what amount of geometry is seen and how it's hitting the geometry as well.

I'll continue to experiment with it and see what I can find out. Thanks for trying it though!