CAP 202 - Computer Animation II

Lesson 1 - Chapters 2 and 4


This lesson reviews some 3D modeling concepts from CAP 201, and begins digging into the project basis for this course. Objectives important to this lesson:

  1. Mapping textures
  2. Mapping types
  3. UV Editing
  4. Review of modeling terms
  5. Creating 3D from 2D
  6. Planning a game environment

We begin with Chapter 2 of the text (page 39) as a carry over from CAP 201, where you learned to use 3DS Max. The text begins with a reference to working with a technology budget: we can only put so many polygons on a screen, no matter how good our platform or our hardware. The actual number will vary from one platform to another, from one year to another (as components change), but the truth we must accept is that we cannot put everything on a screen that we will want to put on it. In a rich game environment, there will be some compromises to make. More on that next week, when we consider chapter 1.

The illustrations on page 40 gives us the concept in a nutshell. We see a three dimensional cube, created in 3DS Max, Maya, or another program. The surface of each side of the cube is divided into numbered coordinates, as we might do when preparing the cube for a UV map. A texture map customized to this cube has been applied to it in the second illustration, showing us that the texture map can give the illusion of a detailed object (a crate with seven boards on each side, plus a frame) when in fact our object has only six polygons.

In this section the author makes a distinction between the terms texture and skin. In his terms, a texture is art that may be tiled (or may not) on the object it is applied to. A skin is art that is applied to a character or other object that requires a lot of detail. A skin would generally be required for objects that will be seen in close-up shots in a game or movie, as opposed to objects that will only be what might be called scenic or stage dressing objects. Those objects are typically seen at a distance, and would only require simpler textures.

The text reviews several mapping types found in most 3D design programs. Mapping types are more accurately methods for applying a texture to an object:

  • planar - useful for flat objects, like walls, but not good for objects that will be seen in 3 dimensions. Note the smearing effect illustrated on the sides of a head on page 43. The planar mapping loses its appeal on the sides of an object.
  • box - box mapping assumes that the object has six regular sides, like a cube. It fails on sides that are uneven or bumpy.
  • spherical - as illustrated on page 45, spherical mapping starts with a flat rectangular image that is wrapped around a sphere. There will be a seam on one side where the edges of the rectangle meet, and there may be distortion at the top and bottom of the sphere as well.
  • cylindrical - like the spherical mapping above, a cylindrical mapping starts with a rectangular piece of art that is wrapped around a cylinder, making a seam on one side. It does not work perfectly with the ends of the cylinder, either.

You should begin to see why we need a custom map, a skin, for any object that is irregular in shape, or that will be seen closely from any direction.

The text continues by reviewing the idea of applying multiple textures to a single object by using sub-objects to receive the textures. The terms he uses in this chapter vary from 3DS Max in only one case:

  • vertex - a point in space included in the object, where two line segments (edges) meet
  • edge - a line connecting two vertices
  • face - can mean what 3DS Max calls a polygon, or a triangular piece of a polygon
  • element - the entire object (although this can also mean component objects that have been attached)

On page 55 the author presents a short list of standard primitive forms that you can expect to be able to make in any modeling software:

  • cube or box
  • cone
  • tube
  • torus
  • pyramid
  • cylinder
  • sphere
  • teapot (Okay, he did not list this one, but you should expect it in 3DS Max)

The next pages review other lessons from CAP 201:

  • mesh editing
  • moving a vertex with soft or hard selection
  • adding a vertex
  • chamfering an edge
  • extrude
  • bevel
  • inset

The author also presents a modeling concept that Mr. Derekshani left out. Several coordinate systems can be used in a scene.

  • object or local space - a coordinate system that uses the pivot point of an object as the origin
  • world space - a coordinate system that uses the center of the scene as the origin
  • view space - a coordinate system that depends on the current view for its origin point

Look at the illustrations on page 61 and compare them to the bulleted list on page 59 to review how splines interact with vertices. For the purposes of this discussion, assume that a spline is a line that is interrupted by a vertex. The spline flows into the vertex's location, then it continues on its way, flowing away from that location. The vertex can be declared to be any of these classic types:

  • bezier corner - has two independent control handles that can affect the portion of the spline entering the vertex independently of the portion of the spline exiting the vertex
  • bezier curve - has two control handles that affect both sides of the spline at once
  • linear - has no control handles, and both sides of the spline are straight
  • smooth - has no control handles and both sides of the spline are curved

The text ends the chapter with a review of some transforms and deforms that can be applied to objects.

Exercise 1: Create a new scene in 3DS Max.

  1. It should be animated to demonstrate the three transforms on page 64 and as many of the deformations on page 65 of the text as you can. Let's say you have to have the three transforms and at least seven deformations.
  2. Use timing effectively: I want to see each transform and deform independently without being rushed. Assume you are going to add a narration that will take at least five seconds for each effect.
  3. Render an AVI movie of this animation (no QuickTime, remember?) and show it to me for grading. It will help if you identify each change in the figure as it happens. Text in 3DS Max, or captions in After Effects? Choose one.

Chapter 4 has only five pages. Here, the author begins a plan for creating an urban environment for a hypothetical video game. A bulleted list is presented (beginning on page 99) of things we need to know before we can work on a game:

  • development technology - what hardware/software will we use to create the game and the game assets?
  • platform technology - what platform(s) will the game be played on?
  • game perspective - first person? third person? selectable?
  • game theme - what is the setting and the point of the game?
  • game genre - what kind of game is it?
  • game fiction - what is the story of the game?
  • world maps - how big is the game world? what is its shape?
  • concept art and references - what ideas can we or must we use when we create assets?
  • asset list - finally, what must we create for the game?

The author answers most of these questions as he prepares us to work on the set of a grand prix style auto racing game.