CAP 211 - Interactive Design and Game Development

Chapter 36 - Using Space Warps

Objectives:

This lesson discusses several varieties of space warps. Objectives important to this lesson:

1. Creating space warps and binding them to objects
2. Types of space warps
3. Space warps and particle systems
Concepts:

New chapter, and new concepts. Space warps are like modifiers that can be applied to multiple objects in a scene. Some space warps are specific to one object. Objects can be affected by more than one space warp. A good tutorial on space warps is presently available at this link.

Most of the examples define how the warp affects a particle stream. Yes, I know, we didn't read the chapter on particle streams. Think of a particle stream as flowing water, or a beam of energy. Both ideas are appropriate here. A space warp will affect the flow of particles. Sometimes all particles in the stream are affected the same way, and sometimes they are affected differently. Think of a laser hitting a mirror at a 45 degree angle. What happens? The coherent light is reflected by the mirror, at an equal but opposite angle. Optics law: the angle of incidence equals the angle of reflection.

Now, think about what happens when a stream of white light goes through a prism. The beam is split into component wavelengths, and the various new beams of light come out at several different angles to make a spectrum. In the image on the right (from Wikipedia) we see a nice simulation of a particle beam being refracted by a prism. (In the real world, there would be some reflection as well.)

The text describes a seemingly endless list of space warps. Let's try to organize it a bit:

Force Space Warps

• motor - applies a twist
• push - applies acceleration
• vortex - applies a spiral, whirlpool force
• drag - applies a dampening, slowing force
• PBomb - used to blow up PArray objects
• gravity - causes objects to accelerate toward it
• wind - causes acceleration away from it
• displace - pushes like a force field

Deflector Space Warps
P is for Planar, S is for Spherical, and U is for Universal which means it takes the shape of another object.

• PDynaflect, SDynaflect, and UDynaflect - these all reflect
• POmniflect, SOmniflect, and UOmniflect - these reflect but they also refract: they bend and change the speed of particle beams that pass through them (set a percentage for how many particles are reflected/refracted)
• Deflector, SDeflector, and UDeflector - just simpler versions of the set above (legacy support?)

Geometric/Deformable Space Warps

These warp the surface of objects, e.g. applying a ripple to the surface of a pond. The pond surface would have to be bound to the warp, but the effect on the pond will be determined partly by the placement of the warp. This introduces another warp related idea: warps affect spatial volumes. The warps below will affect objects that are bound to them, but those objects will be affected differently depending on where they are located in the space that the warp affects.

• Free Form Deformer Box (FFD Box) - deforms the surface of a bound object
• Free Form Deformer Cylinder (FFD Cylinder) - deforms the surface of a bound object
• wave - applies linear waves to a bound surface
• ripple - applies radial waves to a bound surface
• displace - deforms a surface in a sculpted way, or matching the surface of another object
• conform - forces an object to wrap to the surface of another object
• bomb - blows up an object; fracture points are based on the faces of the object

Modifier-based Space Warps

As the text explains, these are like the modifiers you have already seen and used, but since they are space warps, they can be applied to multiple objects in a scene.

• bend
• noise
• skew
• taper
• twist
• stretch
Tutorial Notes and Questions

Tutorial 1 (Creating pond ripples):

2. Follow the instruction to create a ripple space warp. Set its amplitude and wave length as instructed, for the moment.
By the way, as the next chapter will tell you, an animator should know something about physics.
Question 1: What does amplitude mean in this example?
Question 2: What does wave length mean in this example?
3. Bind the patch object (water surface) to the space warp as instructed.
4. Consider other settings for amplitude and wavelength. Show me the effects of your other settings in class.

Tutorial 2 (Blowing a dandelion puff):