CS488 - Introduction to Computer Graphics - Lecture 22

Comments and Questions

Review

1. Intersection Tests

Projects

The idea is simple:

1. Think about what you want your result to do and to look like.
2. Choose technical objectives that make your result better than it would otherwise be
   • Some should be easy; some hard.
3. Make an implementation plan
   • Should be incremental: you might not get completely finished :-).
4. Implement
   • Should do your easy objectives first.
5. Demo your project
   • Should be able to show the effect of your technical objectives clearly
   • On-off toggle for interactive projects; sample images for others.

Types of Projects

Contemplative

1. Still image
2. Animation
   • Static
   • Dynamic

Interactive

1. Game
2. Visualization

Subjects for Projects

Architecture

Art

Game

Geometry

Nature

Simulation

Rendering Style

Photorealistic

• OpenGL
• Ray Tracing

Non-photorealistic

Objectives

Resources

For what to do

• A5 assignment description on the web page; it's long but everybody ahould read all of it.

For project ideas

• Previous CS488 projects

For possible objectives

• The last half of the course notes

More Ray Tracing

Recursive Ray Tracing

Just what the name says, but why would you do it?

1. Unusual light paths for illumination, such as colour bleeding, reflection

Surface Normals

Implicit surfaces, i.e., given by f(Q) = 0.

• Normal is perpendicular to the tangent space n . (Q' - Q) as Q' -> Q for all Q' on the surface.
• Normal is grad f(Q) = i df/dx + j df/dy + k df/dz

Transforming the normal vector

1. Under an affine transformation, M, Q goes to MQ, and Q' goes to M(Q').
2. The new tangent, n1, is defined by n1.M(Q'-Q) = 0.

Constructive Solid Geometry (CSG)

Geometric primitives can make other geometric primitives by

1. union
2. intersection
3. subtraction

The result is like sculpting; the problem is that describing the result is very difficult; the solution is

• Keep the combined primitives uncombined in the model
• Do the set operations on the ray

Texture Mapping

1. Basic
   1. Start with a 2D image: pixellated or procedural
   2. Map 2D image onto primitive using a 2D affine transformation
      • Simple if the surface of the primitive is flat
      • otherwise, ...
   3. Backwards map intersection point with ray into the image to get the surface properties
2. Normal Mapping (Bump mapping)
   1. Start with a difference surface, defined with respect to the surface
   2. Calculate the normals to the difference surface and map them onto the surface of the primitive
   3. Use the mapped surface models for lighting
   4. No occlusion, shadows are wrong, silhouettes are wrong, nobody notices!
3. Solid Textures

Return to:

• Bill Cowan's home page
• Bill Cowan's teaching page.
• Bill Cowan's CS488 page.
• Bill Cowan's CS488 page for Spring 2007.
• Bill Cowan's CS488 lecture note page for Spring 2007.