Adv Computer Graphics CS 6500 Spring 2003 CS

Adv. Computer Graphics CS 6500, Spring 2003 CS 6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003

Announcement • Syllabus. • Course web page. • Copyright notice of SG Course Notes. • Reading: The section written by Eric Haines in SG 01 Course #43. CS 6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003

Themes • Real-time, interactive 3 D graphics. CS 5502 Photorealistic Image Sythesis. • How to draw a lot of polygons fast? – Culling; Simplification (level-of-detail) • How to make them look good? – Real-time shading CS 6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003

How Do You Draw a Picture (Without a Computer)? • What is your subject? • Viewing Parameters: – Camera, Picture Frames, Resolutions • Many ways to specify it: (1) eye, focus length, image plane (2) eye, direction, FOV, up vector CS 6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003

CS 6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003

3 D to 2 D Projection • OK, so we can map a 3 D point (or vertex) to 2 D image. • But what about a 3 D surface? • Polygons are made from points. • Actually, we only need triangles! CS 6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003

Scan Conversion • Also called rasterization. • The 3 D to 2 D Projection gives us 2 D vertices (points). • We need to fill in the interior. CS 6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003

Shading • Interpolation of vertex colors within the triangle? – Looks OK, but not very meaningful in physics. • Interpolation of normal vectors, then light it? – Aren’t the normals always the same for a flat triangle? CS 6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003

An Overview of 3 D Pipeline • The above can be implemented in hardware. • Z Buffer to detect hidden surfaces. • Other transformations not mentioned here: Modeling and Viewing. • Browse Chapters 5 & 6 of Watt’s book if you’re not familiar with it. CS 6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003

…But They Don’t Look Real CS 6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003

• Most things are not flat or simple geometry like spheres and cones. • We need correct surface colors and shapes (and more) CS 6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003

• We also need correct lighting. • Textures help, but not enough. • Even simple things like CD can be challenging. CS 6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003