Sunday, 24 April 2011

The Making Of Project Dragon - Episode 12

Stop! It's Render Time.


Rendering for this project required learning pass based rendering in greater detail. Within Maya, the first step is to create Pass Contribution Sets. These sets have geometry added to them (ie. dragon, nest, grass) so that different render passes can be added to different pieces of geometry within a single render. For example, the nest had the following passes associated to it:

Diffuse
Specular
Reflection
Ambient
Shadow
ZDepth
Motion Vector
Beauty

These passes would enable me to reconstruct the image of the nest in Composite whilst giving me a vastly higher level of control over the final output. For example, I would be able to take a duplicate of the specular layer and add some blur before adding it on top of the main image, thus creating the illusion of glowing hotspots on the nest.

The motion vector pass enabled me to add a reasonably good motion blur effect within composite without adding any significant time onto the render.

Unfortunately, Mental Ray doesn't offer support for pass based renders for the SSS shader I was using for the dragon skin, and no other shader offered me the result I wanted, so I was forced to only produce a beauty pass for this layer.

The final element of note on the render settings is the file format. I used a 4 channel 32 bit OpenEXR file, which Composite is highly compatible with. This would add a lot of power to me during compositing, as well as giving me much fewer files to deal with.
I calculated that if I had outputted each pass as tiffs, I would have required 28 different file sets with 1300 frames for each set. With Open EXR I had 1 image set.

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