Rendering in Passes


Hello Animators.

I am gettting close to rendering out an animation, and for the first time I’m going to Render it out in passes, as I’ve heard and read so much about.

I have 2 question on this subject.

1st. I understand the process, but certain parts I’m unclear about. I’m going to list the process I would go through, and if you guy could let me know if its a efficient way or if, I should do something else. Here I go. Also I am using maya but Its almost the same in all apps (I think)

Render out Background in one pass ( Color )
Render out Characters in another pass (Color, Matte, Depth)
Render out Particles (Color, Matte, Depth (particles in the distance))
Render Glows ( Color , matte )

when rendering the background hide everything that isn’t in the background, render.
For the characters, put a surface shader on everything besides the characters

Pretty much put a surface shader on what ever isn’t the primary thing being rendered . . .?

I’m going to composite later in shake, and I was going to render out sequence *.iff files.

The 2nd part was.

is Rendering out in passes just to speed up rendering time, I know it give you more control over the output of your project because certain elements can be adjusted easier when compositing, but if your animation looks fine in the program your rendering in, is it that much quicker to render in passes than just straight will everything visible ( I know for Maya users Hardware particles have to be compositied in).

Thank you all for your time and any responces.



Usually, rendering in passes refers to rendering a single layer split into a specular, duiffuse, reflection, ambient occlusion, reflection occlusion etc. pass.
These passes are then combined in your compositing app.
Rendering in layers is indeed done as you described. Each element in a scene that should be touched up in comp somehow is rendered as a single layer, which itself ,may be split into several passes.

If you render layers, often you will face the problem of one layer intersecting another one in depth – that is a layer b is not atop layer c and not below layer a but somehow encloses both (think of layers c & a as characters and of layer b as a particle system like dust around them).
In this case you have to include the geometry on all intersecting layers as matte objects when rendering layer b. Matte objects render black and alpha-transparent and occlude geometry behind them.




If you want to render out the scene into seperate physical layers (ie, foreground, midground, background), use the clip planes on your camera to set that up. You will avoid the problems Mauritius described as far as splitting up objects goes.


thank you Mauritius, and Dimitrius.

I knew I had to matte objects, but its always good to hear your on the right track.

Thanks. For the project I’m worknig on, it a small animation project that probably wouldn’t hurt to render out in a single layer, but I am prepairing myself for when I get to the time when I have massive scenes and will need to render out in many layers, I would have already have had experience with it.

Thanks guys.



as was said, passes refer to individual parts of the render then putting it together later. This is a great way to work, you render the color, spec, shadow…etc as seperate layer passes then you put it together in post…the advantage to this is, say you want to change the bg color after its all done (clients are nice like that) you can do so, then change the spec color on the character to go with the BG. Or re-render just certain passes (faster that way).

Rendering in layers as you are saying is good because you save a lot of time. Render the BG in one layer, then your character. Dont hide your bg though when you render the characters jsut use a Background Shader on them so you can get your shadow maps and a nice clean alpha around the characters. This way you can still alter the characters but not quite as individuallisticaly. But you only have to render the BG once (unless your lights are moving) but you can get some nice shadows and render time is cut in half :slight_smile:

have fun!

Happy Rendering!!!


Dont hide your bg though when you render the characters jsut use a Background Shader on them so you can get your shadow maps and a nice clean alpha around the characters.

cool, but…
if i were him i use matte shaded bg, no env. color, PNG format ! :slight_smile:
because of advanced PNG’s alpha channel, no need to render
the characters in front of actual BG’s color.


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