Lecture 1: The Graphics Pipeline

Overview

Motivation: Draw shapes/geometry to 2D screen.

The Graphics Pipeline is the process by which we convert a description of a 3D scene into a 2D image that can be viewed.

This involves both transformations between spaces and conversions from one type of data to another.

• Spaces
  • What is a space? Left/right perspective example
  • Where do we store geometry of scene?
    • “World” coordinates

• Types of Data
  • “Primitives”
    • Simple kinds of figures/geometry
  • Triangle meshes
  • What is a picture?
    • pixels, “picture elements”

$$0 \le x_p \le w - 1$$ $$0 \le y_p \le h - 1$$

We need a way to transform from world to pixel.

General Graphics Pipeline

vertex array: what are the vertices

• input specification

vertex shader: move to camera’s perspective

object space --> screen coordinates

rasterization: which pixels are inside triangle?

fragment shader: what color is each pixel?

testing and blending: which pixels are visible?

Software Rasterizer

1. Read in triangles
2. Convert triangls to windows coordinates
3. Rasterize each triangle
   • (use barycentric coordinates to test in-triangle AND interpolat colors)
4. Write interpolated color values per pixel (using a z-buffer test to resolve depth)

Labs

Lab 1

• Compute bounding box
• Draw box and vertices

Lab 2

• Compute barycentric
• Check is-interior?
• Interpolate colors