CS662 Computer Graphics Game Technologies

Jim X. Chen, Ph.D.

Computer Science Department George Mason University

Contents

• Tentative – Alan Watt and Fabio Policarpo, Advanced Game Development with Programmable Graphics Hardware – Games we are interested in implementing – Technical approaches – Survey and presentation

Introduction and Cg Programming

• The Hardware Model (Fig. 1.1, P3) – GPUs are highly programmable – They can carry out general computation – NVIDIA’s Cg, OpenGL 2.0’ Shading Language (GLSL), and DirectX 9’s High Level Shading Language (HLSL) – they are similar – “Shader” signifies a vertex, or a pixel or both together – The output of fragment program is a value for a pixel

The Hardware Model

• GPU programming involves a vertex program and/or a fragment program. • Cg is not application specific, may be used for parallel computing, for example. • GPGPU – general purpose computation on GPU.

The Hardware Model

• Vertex processor – Transformation, primitive assembly (lines, polygons), clipping, rasterization resulting in a set of pixel locations and fragments – A fragment is a potential pixel • Fragment processor – Fragment operations such as texture mapping. Result imy be a color (framebuffer) and a value (z-buffer) • Example: Gouraud shading and Phong shading – Gouraud shading needs vertex processor to calculate lighting at a vertex – Phong shading needs a fragment processor to calculate lighting at a pixel

Programming Overview

• The Programming Model (Fig. 1.2, P6) – Data is streamed into the processor and operated on by a kernel function (fragment program) – Up to 16 arithmetic processors operate on the stream, and each data element is processed in parallel – There is no dependencies between elements – A shader is written to operate on a single vertex or fragment and is executed on every vertex or fragment

The Programming Model

• Parallelism works in rendering and related applications that have no communication between processes • GPU fragment programs reads from texture maps and write to the framebuffer – May need to copy the results from the framebuffer back to texture maps. • Hardware limits are expressed by profiles

The Languages