This function is not available in all 3D applications.
PLA allows the user to make alterations of a model from the point level or the level of the model where polygons meet.
The ability to animate these sorts of movements allows for great facial animation with changes in the visual makeup of the face.
For instance, a simple set of eyeballs made from primitive spheres, and a set of eyebrows constructed from a sweep NURBS object.
The spline that defines the curve of the sweep NURBS was animated using PLA to give the eyebrows a wide range of expressive qualities.
A basic tenant of animation is that movement is simply a sequence of slightly different images that when shown in rapid succession give the illusion of movement.
So, if an animation is displaying 30 frames per second (fps), then a three-second animation has to render 90 frames.
These types of rendering times begin to add up.
For this reason, it is very important to create "preview" animation of movement.
Preview animations are renderings of the motion you have created so far that is rendered using one of the preview renderers (gouraud, OpenGL, wireframe, etc.
).
Although this will not give you the specifics of how light or textures may be playing off each other, it will give you a good idea of how the timing is working out.
It is much less painful to find out that your ball is bouncing through the floor or that the ball is bouncing too slowly after you have waited 30 seconds for it to render as an OpenGL rendering, than it is to find it out after waiting 15 hours for a raytracing rendering.
Once you have seen that all the motion is happening at the speed you wish, then do a raytraced rendering.