3D Concepts

Animating in 3D is still done with the techniques covered in incremental, parametric, and recorded animation, but in three axes and using a 3D rendering algorithm.

A 3D rendering algorithm attempts to give the illusion of depth. This illusion is created with a variety of visual cues that trick the human mind into thinking a two-dimensional image is three-dimensional. Some of them:

• relative size. Objects further away appear smaller.
• relative speed. Objects further away appear to move slower.
• z-axis blocking. Objects nearer appear in front of objects further away.
• haze. Objects further away are obscured by particles in the air.
• perspective. The apparent dimensions of an object taper as they get further away. Relative size and speed are also a result of perspective.
• light reflection/shading. The way light reflects from an object indicates its three-dimensional shape, and its position in relation to the light source.

The 3D rendering algorithm creates these depth cues based on model variables.

Z-Axis
Incremental Animation
In an incremental animation in 3D, variables z, zVelo, and zAccel are used along with the x- and y- axis variables of the physics model. Using the vector data type makes this alot simpler. Instead of using separate x, y, and z variables:

xAccel = xForce1 + xForce2 + ...
yAccel = yForce1 + yForce2 + ...
zAccel = zForce1 + zForce2 + ...
xVelo = xVelo + xAccel
yVelo = yVelo + yAccel
zVelo = zVelo + zAccel
x = x + xVelo
y = y + yVelo
z = z + zVelo

The vector data type can be used to do the same thing:

vecAccel = vecForce1 + vecForce2 + ...
vecVelo = vecVelo + vecAccel
vecPos = vecPos + vecVelo

Parametric Animation
In parametric animation in 3D, x, y, and z position variables are also used. In the parametric demos the loch and locv properties were set without using intermediary x and y position variables, but with 3D they will be used. There will be an animator function for z in addition to those for x and y.