Rendering a video in passes

I was just thinking how to render a video in passes. Like an AO pass, shadows pass and so on. :rolleyes:

According to the release notes, only the RGBA, Z, normal, and vector speed passes are explicitly available in 2.42. So I still use old-school methods, like getting a diffuse-only pass by turning off Spec for all the lights, as well as turning off CMir textures and shadows. I’ve been able to extract spec, reflection, shadow, and AO passes similarly. Some of it could be streamlined by using nodes but you’d still have to play with the lights. I hope the next release has more useful compositing passes.

If you want more details on how to produce specific passes and composite them I can write up a list.

But is there any other good way to render a video in stages. Not all at once.
I dont have enough free time to render videos as a whole.

Dear CD38,

I would really appreciate if you can share your setting for render passes. This is the issie that I am trying to solve for some time, but the results are still not OK. Please be so kind and desribe the render settings in matter, mainly AO, Spec and Shadow pass.

I know that also Colin Levi in Suburban Plight Thread desrbide short of but really very breafly and in general.

Thank you very much in advance.



in a weird way, your passes are much less reliant on the render than they are on your post production compositing, I think you’d be surprised what you can do/fix with compositing. basically, create four different unlinked scenes and then turn off all diffuse shading, background, and tone your lights for your specular pass, turn off all spec shading for a color/beauty pass, do the same for reflections, bump-mapping, raytraced shadows etc. Go out and buy Digital Lighting and Rendering by New Riders. it goes into some real depth about render passes and teaches you a lot about how materials, light work in the real world, as well as compositing, which is really too complicated to explain here. really an excellent book and a cool read. Texturing and Painting is excellent too but I’d stay away from digital directing and cinematography. that one sucks. I’d also buy aftereffects if you can afford it; oddly and unlike blender, the free alternatives can’t touch it yet…

This method is labor-intensive but it gives acceptable results, considering it is done entirely in Blender. As I said I haven’t tried to combine the approach with node-based materials. Here is how I set up all the passes; make sure to work on a duplicate of your blendfile, and Save As after changing the settings!

Diffuse: set all lamps to No Specular, turn off AO, uncheck any textures that map to Cmir, and turn off Shadow in the Render panels.

Specular: set all lamps to No Diffuse, uncheck any textures that map to Cmir, turn off Shadow in the Render panels.

Shadow: Make the world color all white, turn on Only Shadow (Shaders panel) for all materials. Make sure Shadow in Render panels is on.

AO (raytraced): Set all materials to pure white and the world to black. Turn on AO and Raytracing.

Render each of these passes. Combine the resulting files as strips in the Sequencer following this formula:

((diffuse * AO) + specular) * shadow

It’s a lot of work to produce each pass, but it can speed up making the final adjustments when you’re compositing. I don’t have any high end commercial software do I have no idea how this compares to using those packages. I have been playing around with producing bump, fresnel, reflection, and particle passes too but they are proving to be much more difficult.

Edit: I agree, Digital Lighting and Rendering by Jeremy Birn is an awesome reference. It’s in its 2nd edition.

@blenderist: For video/animation, you could apply this technique and render each pass to multiple files, then composite as described. Is this what you meant by rendering a video in stages?

Thank you very much this is very kind of you. Do I have to modify lights for AO pass and which lights are most suitable (probably sun?)


I usually move all lights to a non-rendered layer for the AO pass. But it depends on your AO settings and the look you are after. This is usually the pass I will tweak the most, and since it’s slow, it’s when I really appreciate compositing!