An Overview of the Rendering Pipeline

An Overview of the Rendering Pipeline
In "Modern" OpenGL

Computer Science Department

bernstdh@jmu.edu

Introduction

The "Classic" Fixed Pipeline:
- The programmer specifies shapes, colors/textures, and the environment; the pipeline then does the rendering
The "Modern" Flexible Pipeline:
- The programmer specifies shapes, colors/textures, the environment and the rendering algorithm (using shaders

The Programmer's Responsibilities

The Pipeline

Vertex Processing:
1. Each vertex is processed by a vertex shader
2. Each vertex may be processed by a tesselation control shader and tesselation evaluation shader
3. Each vertex may be processed by a geometry shader
Vertex Post-Processing:
1. Transform feedback
2. Clipping and transformation to window space
Assembly of Primitives
Generation of Fragments (i.e., Rasterization)
Fragment Processing
Per-Sample Processing:
1. Scissor, Stencil and Depth Tests
2. Blending
3. Logical Operations and Write Masks
4. Others

Vertex Specification

Vertex Rendering

Primitives:
- As in "classic" OpenGL (e.g., GL_POINTS, GL_LINES, GL_TRIANGLES, etc...
Initiation:
- Using a drawing command (e.g., glDrawArrays()

The Necessary Shaders

Vertex Shader (Mandatory):
- Converts each incoming vertex to exactly on outgoing vertex
Fragment Shader (A "Default" Can Be Used):
- Converts each incoming fragment (i.e., group of pixels) into a list of colors for each buffer, a depth value, and a stencil value

There's Always More to Learn