‘Rezzing’ a light cycle part II: rendering and compositing

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Here’s part II of ‘Rezzing’ a light cycle. In the previous post, I discussed the fx animation part of this effect. In this second part, I want to get into the shading, rendering and compositing.

As in Part I, I’d like to start with showing a breakdown version of the close up rezzing animation:

View in full resolution: trnd_rez_breakdown2_v01.


The shading of the cycles was fairly straight forward. The cycles in Tron seem to be mostly about reflections and glows, which aren’t really the most difficult thing to achieve.


For the body of the cycles, I started with a standard: ‘Mantra Surface’ shader.
I used a very weak diffuse component with a dark blue color just to define some of the area’s, which don’t get reflections.
The reflections use both light and object reflections. The light reflections take care of specular highlights and reflections of the environment light that uses an intensified and blurred version of the background image (spherical). These reflections create most of the look of the bikes.
Lastly, I used modified the shader to use a ‘wire_pattern’ as the intensity input for the emission channel. This is used in the ‘rezzing’ passes to add the glowing wire frames around the fragments before them blend in with the completed cycle. The wireframe intensity is attenuated using the same ‘gen’ attribute that drives the ‘rezzing’ animation. The shader has a ramp parameter that controls how this ‘gen’ attribute is translated into wire frame brightness.
For the glowing parts (the lines and engine), I used a ‘constant’ shader that output its results into a custom output channel. These are colored slightly blue or red (depending on the cycle), but most of the color in the final version comes from the blurs that have been applied in the comp.

Transmission and Engine

For the Transmission and Engine parts of the animation, I used the same ‘constant’ shaders. These are separated into a ‘core’, which is bright white and ‘transmission’, which is slightly blue. The ‘core’ shader is used on the rotating circular part in the core of the engine.


After experimenting with different options, I ended up rendering with Mantra’s Micropolygon engine, which ended up giving me a nice balance between performance and quality. Especially with the extreme motion blur of the second sequence in the complete animation, performance and quality of the motion blur was best with micropolygon (achieving the same blur quality with ray tracing required much higher sampling settings to get the same quality).

The animation was rendered in three separate passes:

– ‘rezzing’ of cycle body

– ‘rezzing’ of engine and transmision

– fully ‘rezzed’ cycle (high res geometry)

The body (both ‘rezzing’ and fully rezzed) were rendered with separate reflection, refraction (engine behind glass), diffuse and glow passes. The engine and tranmissions render consists of two render passes one of each of the glow colors.


The compositing was kept pretty basic again considering the time constraints. There are basically three main sections following the three renders. The two body renders (‘rezzing’ and ‘rezzed’) consist of a part that combines the main render passes and one that adds glows to all the light elements.

The glows have been achieved using a higher intensity, small blur in the color of the light (blue in this case) with a lower intensity, wide blur in almost white. These two combined are simply ‘plussed’ over the ‘body’ passes.

The engine + transmission part consists of only light and are similarly blurred.

The ‘rezzed’ cycle is ‘wiped’ over the ‘rezzing’ cycle using a simple animated roto mask.

This concludes the two part discussion on the ‘rezzing’ of the light cycle. In upcoming posts, I’ll go into the creation of the exhaust walls in the rest of the animation sequence.