Getting the look ‘in the zone’

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I thought I’d first go into the advanced tab of the ‘look’ area of the tool. These advanced parameters deal with defining the shading zones on the wave surface. In order to understand these zone definitions you first have to understand how the wave surface is constructed and the concept of ‘wave time’.

The wave surface is created by a number of ‘wave profiles’. We’ve seen these profiles in the previous post. Each profile is created as a blend between ten profile curves. Each of these curves represent a ‘keyframe’ in the ‘wave time’ of a wave profile. Wave time represents the life cycle of a wave from starting flat to breaking to going flat again.

The following image shows the different profiles:

Picture 35

Now, back to the wave zones and the ramp parameters. For each of the ‘keyframes’ of the wave profile there is a ‘ramp’ that defines how it is divided into zones. In total there are five zones (0 to 4). The ramp represents the profile curve from behind the wave to the front of the wave (from left to right on the ramp, Ramp parameters in Houdini always have values from 0 to 1 on horizontal and vertical axis). The vertical axis of the ramp represents the zones. So, if the value 0.5 (the middle) of the ramp has value 0.3, this means that the middle of the wave will be in zone 3 or 4. Value 0.3 is the highest allowed value in the zone ramps but it’s used to define both zone 3 and zone 4. The reason for this is as follows. Zone 3 and 4 represent the lip of the wave as it crashes down into the trough of the wave. For shading purposes it helps if its possible to shade the upper and lower surface of the lip separately. So ramp value 3 defines both zone 3 and 4, where zone 3 represents the lower surface of the lip and zone 4 the upper surface of the lip. The separator between these two zones is defined by the exact center of the wave profile, which is the tip of the lip. Note that ‘center’ in this case means the parametric center not the visual center.

An example of such a curve looks like:

Screen shot 2009-11-11 at 1.54.56 PM

As the ramp automatically interpolates between points all the zones blend into each other nicely. The following image shows the visualisation of the zones that can be turned on in the tool. To make it easier to define the zones a ‘discreet’ view is available that shows the zones with hard boundaries.

Picture 32

The next image shows the zone 3 and 4 as they define both sides of the lip:

Picture 34

The next image shows the blended zones as they are used by the shaders.

Picture 33

I guess you can see why this is the ‘advanced’ part of the look development. It typically doesn’t need to be touched when shading waves as there are sensible defaults build into the wave tool. When it needs to be tuned for a specific situation any TD should have little problems setting up new zones or changing the default zones.

In a following update I’ll get into the actual look of the wave and discuss shaders and how they work with the zones to provide artists with very deep artistic control over the final look of the wave.