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Author Topic: Cutting down the render time  (Read 1922 times)


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Cutting down the render time
« on: November 22, 2009, 05:55:21 pm »

Lately I've read a lot of posts about the Anim8or renderer being too slow and I thought I would post several tips on how to speed it up.

Some golf players say "There's no bad weather...just bad clothing". The same goes for the Anim8or renderer. There's no slow renderer... just wrong scene setups, wrong renderer configurations and impatient users.

Rule #1: Be patient.
This will not speed up the rendering process, but it's the most important rule. If it takes an hour or 2 to render a complex scene, there's no need to worry. If it takes a day or 2, then you should read the rest of this post.

Rule #2: Do not use the ART Raytracer unless you have to.
The good old Scanline renderer is much faster and if you do not need reflections, refractions or special shadow effects, there's no reason to use the ART Raytracer. You can also use environment maps to simulate simple reflections using the Scanline renderer. I think people forget about that...

Rule #3: Decrease the image size.
Large images take longer to render, that's not surprising. If you are not planning to use the image as your desktop background, you definitely do not need higher resolution than 1024x768. I think 800x600 is the perfect size in most cases.

Rule #4: Decrease the polygon count.
This rule is pretty obvious, but many people ignore it. Objects that are far from the camera do not need that much detail. In some cases you can replace your objects with extremely simple low-poly models without any impact on the quality of the final image. You can also fake details using textures and hide all non-visible objects.

Rule #5: Decrease texture sizes.
Before using a 1024x1024 (or even larger) texture, ask yourself: is it necessary? Good textures are the key to a good looking image, but too large textures increase the render time significantly.

Rule #6: Do not overuse bumpmaps.
Bumpmap textures have a strong impact on the render time.

Rule #7: Not all the lights in your scene have to cast shadows.
In real life every light source creates a shadow, but unfortunately shadows take very long to render. If you disable shadows for some lights, there might not be any visible difference in the final image, but the renderer performance will be much better. You can also fake some shadows using textures.

Rule #8: Decrease the RayDepth value.
Ray depth determines how many times each ray is reflected/refracted. Setting a lower value will boost up the performance of the ART Raytracer, especially if there's a lot of glass in your scene. The default value of 12 is usually more than you need, a very low value (such as 3 or 4) usually does not make any visible difference. See the image attached to this post. One of the spheres was rendered with the default RayDepth setting (12), the other one was rendered using the value of 2. Can you see any difference?

If you want to change the RayDepth value, go to the scene mode and click "Scene > Attributes...". Click "new", write "RayDepth" (without the quotes) and click "Ok". Select the "int" option and then type a number to the textbox below.

Rule #9: Decrease the number of AA samples.
Make sure you are not using more AA samples than you actually need. I always set the number of AA samples to 4 when making test renders and then I increase the value until I get what I want. If you're not using the Ambient Occluder, a value of 64 or (at most) 100 should be enough.

Rule #10: Render the AO pass separately.
The Ambient Occluder requires a very high number of AA samples (at least 144) if you want a grainyless image. When rendering the AO pass separately, all the materials are white, there are no lights, no shadows, no reflections or refractions. Therefore you can use a very high number of AA samples without having to wait for ages...
However, you'll need an advanced image editor (such as Photoshop or Gimp) to combine the AO pass with the main render.

Rule #11: Sometimes Photoshop is faster...
Post-production is a part of the process. Some special effects (such as lens flare, glowing lights etc.) can be created in Anim8or, but they increase the render time. If you have Photoshop or other advanced program, you do not need to wait for the Anim8or renderer...

Rule #12: Read rule #1 once more!

Ok, that's all. Any questions and more tips on improving the performance are welcome!


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Re: Cutting down the render time
« Reply #1 on: November 22, 2009, 06:25:41 pm »

Splendid post, Kubajzz :)

Maybe one more rule : Chroma Keying for animations
When the scene is complex to render, render it once without the animated object(s). Then render the animated objects on their own against either a plain green or blue background and when finished combine the two. It saves a lot on render time.


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Re: Cutting down the render time
« Reply #2 on: November 23, 2009, 02:27:01 am »

The 8th rule about RayDepth value was very useful for me.  I always forget about changing that, should help a ton though.