Adding Automotive Bones


I use a method to add bones that is logical and consistent, at least to me.

The first rule is: DON"T MOVE THE BLACK BONE.

In model mode go to a side view and turn on the grid. See the horizontal blue line? In my world this XZ plane is the ground. I select and maneuver the entire model to put it in its typical at rest position on the ground with the vertical Y axis runnning more or less through the model's center and the model facing forward (facing down in a top view). Now turn on bones mode, select the models name in the project workspace and the black default bone appears with its base at X,Y,Z = 0,0,0 and its small end pointing in the +Z direction. It's base is the point in space that will move along a choreography defined path, pulling the rest of the model along for the ride.


Call it main, primary, base, I call it com for centre of mass (Hey, I'm an engineer, I'm programmed to think this way) and I position it within the model to define the point around which the object would tumble if it got thrown over a cliff. This is the bone you move in an action to move the object off its path.

Here's how I set up the bones for a vehicle. The red bone is the com to which all other bones are attached such as the axles (light blue) and the body (bright green). The body bone is positioned so that it will roll about the suspension centres. The front axle bone is a child to the com bone and is oriented in the axle's centre so that rolling the bone causes the axle to tilt from side to side. At either end of the axle is a pivot; basically a short vertical cylinder with an arm sticking out of it. Each pivot's bone is a child of the axle and is oriented vertically in their centres so that turning the roll handles causes the pivots to swivel. The wheel bones are children of the pivots and are oriented such that turning their roll handles, turns the wheels.


The steering wheel bone is a child of the com bone. The pivots are constrained to "roll like" the steering wheel bone. By setting the constraint percentage to less than 100% you can make the steering response more realistic.

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