08-17-2017, 12:16 AM
GPUs - Graphics Processing Units
[attachment=431]
Introduction
Before we dive into the architectural details of some example GPUs, we'll have a look at some basic concepts
of graphics processing and 3D graphics, which will make it easier for us to understand the functionality of
GPUs
What is a GPU?
A GPU (Graphics Processing Unit) is essentially a dedicated hardware device that is responsible for translating
data into a 2D image formed by pixels. In this paper, we will focus on the 3D graphics, since that is
what modern GPUs are mainly designed for.
Geometry Stage
This stage is also referred to as the "Transform and Lighting" stage. In order to translate the scene from
3D to 2D, all the objects of a scene need to be transformed to various spaces - each with its own coordinate
system - before the 3D image can be projected onto a 2D plane. These transformations are applied on a
vertex-to-vertex basis.
Mathematical Principles
A point in 3D space usually has 3 coordinates, specifying its position. If we keep using 3-dimensional
vectors for the transformation calculations, we run into the problem that di erent transformations require
di erent operations (e.g.: translating a vertex requires addition with a vector while rotating a vertex requires
multiplication with a 3x3 matrix). We circumvent this problem simply by extending the 3-dimensional vector
by another coordinate (the w-coordinate), thus getting what is called homogeneous coordinates. This way,
every transformation can be applied by multiplying the vector with a speci c 4x4 matrix, making calculations
much easier.