Houdini Frog Generator - Controllers and Foot Webbings

June 4, 2019

Houdini Frog Generator

Controllers and Foot Webbing

Foot Webbing

The general concept was to take a line of points and move every other one along its normal to create a general zig-zag pattern. Then, you resample it to make it smoother and wavier. I have another set of points that are along the foot that will create the inner boundary of the webbing. You then use the Add SOP to create a closed polygon between these line boundaries.

To make this more consistent, I wanted to create the line using points from the toes. This way, the webbing will follow the toes around properly as I shift them around. This was easy to accomplish by just adding another point at the tip of the toe geo and setting it to have an id attribute of 0. I could then connect all of the same attribute valued points in a line with the Add SOP.

The line between all of the toes would then be made up of a number of points equal to the toes. I needed to add a single point between each pair of toes to move to create the wave in the webbing. This could be done with a resample that adds a point in the middle of each polygon.

Controllers

I wanted to practice setting up overall controllers to start making it easier to work with my frog generator from a few ruling nodes.

I first practiced this by setting up a controller for the foot to control the webbing parameters. This controller was tied to: webbing length, webbing curvature, and webbing origin.

The length is how much overall area the webbing covers between the toes. The curvature is how wavy, or how far the inner webbing points are away from the general curve. Finally, the origin just helps move the inner boundary of the webbing around in case it is too far from the foot or too far in.

I then moved on to creating a body controller, which had a lot more parameters. This also required connecting some ramp parameters, which are a bit weird in Houdini.

These parameters include:

• Body Length
• Spine Shaping
• xScaling Body
• yScaling Body
• Dorsal Start
• Dorsal End
• Dorsal Projection Angle
• Dorsal Projection Ramp
• Back Leg Position
• Back Leg Angle
• Arms Position
• Arms Angle
• Eyes Position
• Eyes Angle
• Tympanum Position
• Tympanum Angle

The body length is just the general overall length of the body shape. The spine shaping is a ramp that lets you add curvature to the body. The xScaling and yScaling are ramps that independantly alter the general width or height of the body throughout.

The dorsal variables control the larger dorsolateral dermal plica on the back of the frog. These are raised ridges a lot of frogs have. These control how far along the frog's body these ridges go, the radial angle around the body they are projected, and a ramp to control how much it deforms the general body in the normal direction along the ridges.

Finally, all of the positions and angles control the connection point locations for various body parts of the frog to the general body. These select a specific point along the main spine to project out onto the body surface, and the angle determines the radial projection around the body these points are located. These two features together let you place the body parts anywhere on the body very easily.