[Bf-committers] render passes & workflow

[Matt Ebb]

On 07/12/2006, at 00:19 AM, Ton Roosendaal wrote:

> Hi,
>
> Now that the basic code work was done, it's time to check on  
> usablity of pass rendering.
> (No Trip, not usuability of compositor, that's another project!).

Right now, the object ID pass doesn't seem that useful, they pretty  
much just give me a black and white image that it's hard to do  
anything useful with, and similar enough to just putting that object  
on its own render layer anyway. Having to tweak number buttons and  
assign an ID to each object manually is a real chore and it seems a  
similar approach to Cinema 4D, where it's mostly used as a workaround  
for having no render layer system like we do. Also unlike other apps,  
none of our nodes have an option to selectively apply effects to  
certain object IDs, and I don't think that really fits with our  
compositor either.

Something that I've used before when working on some architectural  
rendering stuff (though I'm not sure exactly which app rendered the  
images) is an object ID pass that includes every object, with random,  
non-antialiased RGB colours. I presume it generated each colour based  
on a hash of the object's name or something like that, and in this  
particular scene there were so many objects I seriously doubt the IDs  
would have been assigned manually. Anyway, it looked a bit like this:  
http://mke3.net/blender/etc/obid.png

It was great because I could then go into photoshop and interactively  
tweak the appearance of individual objects, just by using simple  
masking. Now that we have the nice chroma key nodes and the colour  
picker eyedropper, it's extremely easy to do the same thing in  
Blender - see this node setup:
http://mke3.net/blender/etc/obid_nodes.png

The packed file is here:
http://mke3.net/blender/etc/obid.blend.zip
- you can see how easy it is to pick other objects to isolate, using  
the eyedropper, and it's easy to include additional objects just by  
adding a new difference key and adding the mask on top.

Doing the object IDs like this would be better since it'd:
* be much easier to use
* be more flexible for going back and tweaking things without having  
to re-render - i.e. currently if I decide later on that I want to  
tweak some object that I didn't previously assign an ID to, I have to  
assign it and re-render the entire thing again. If every object has  
its own random colour from the start, I'm much more free to  
experiment or change my mind
* allow people to also do their edits easily in external image  
editing or compositing apps of their choice too, not just Blender.

cheers

Matt


------------------------------------------
Matt Ebb . matt at mke3.net . http://mke3.net



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