praseed pai

3D Computer Graphics - a Technical Introduction

AKA 3D Graphics Programming !

ByPraseed Pai K.T.

http://praseedp.blogspot.compraseedp@yahoo.com

Background

UT Game Engine Release Discussion in the BarCamp user Group Volunteered to take a session on Graphics

Programming Aspects Has in the past consulted for companies in the

CAD/CAM space. Lack of Graphics Programmers in Kerala

( INDIA)

Computer Graphics – What the heck is it ?

William Fetter in 1960 coined the term Ivan Sutherland's Sketch Pad Thesis @ MIT

Part - 1

PIXELS !

What is a Pixel ?

Pixel or Picture Element is a 32 bit integer value

RGBA – Red Green Blue Alpha One can use an array of unsigned integers to

store the pixel data. Once the data is populated , we can transfer

the stuff into a Windows Device Independent Bitmap.

After Pixels , what else ?

Bresenham's Line Algorithm

Midpoint Circle Algorithm

Triangle , Rectangle , Polygon Filling

Copy the Stuff into the Device

Demo

Clear the Screen Background Plotting Arbitary data at a point Rectangle,Triangle , Circle , Arc Rasterization

demo Image Point Processing ( Color to Grey Scale

and Image Negative ) Procedural Image

Part 2

Transformation and Matrices

2D Physical Co-ordinate System

Transformation

Translation Rotation Scale

Logical Co-ordinates

Demo

A Clock Program using MFC Manual co-ordinate Transformation. Clock Geometry

Part 3

Finally it's 3D Time

3D Co-ordinate System – Are you on the Left or Right ?

3D Transformation - Translation

3D Transformation - Rotate

3D Transform - Scale

3D Viewing - Perspective

3D viewing – Perspective Matrix

3D viewing - Ortho

3D viewing – Ortho Matrix

Primitives

Primitives ( contd.. )

Jim Kajiya and his Rendering Equation

Lights Please

Rendering A scene using Global illumination

Numerical Evaluation of Rendering Equation

Computationally Very Expensive Monte Carlo Rendering Global Illumination Algorithm Radiosity , Photon Rendering , Bidirectional

Path Tracing , MetroPolis Light Transport Algorithms solve the Rendering Equation to determine the Pixel Color

AQSIS – A RenderMan Compliant Renderer

How do i Light in a feasible manner?

Local Illumination Models

Global Illumination by solving Rendering Equation is not suitable for Real Time Graphics

We go for Approximation algorithms to create illumination models which are close to the physically based models

Phong Lighting Model with Gourord Shading ( more about it later ) was the only feasible thing for real time work.

Thanks to GPU we can have per pixel lighting like Phong Shading.

Phong Lighting Model

Phong Lighting Model

Shading – Flat Shading

Every Polygonal face will have same color Fastest Shading Method Visual Fidelity is not good

Shading – Gourord Shading

Calculation is done per vertex The Colors are interpolated

Shading – Phong Shading

Per Pixel Lighting Calculation Most Expensive Feasible only on a GPU

Lights – Directional Light

Lights – Point Lights

Light – Spot Light

Images , so far ar synthetic .how do i add details ?

Texture Mapping - Adding Detail to the surface

Texture co-ordinates

Demos

Texture Mapping an Image on to a Quad Environment Mapping Demo Terrain MultiTexturing Fog Demos from Ultimate Game Programming book

Duo Who made PC a graphics Platform

Part 4

Procedural Techniques

GPU

Aka Graphics Cards Became Programmable from 1999 Now one can write code using High Level

Languages Cg from Nvidia GLSL from OpenGL ARB/Khronos HLSL from Microsoft Modern day GPU

Graphics Pipeline

Demo – Ambient Light Vertex Program

//////////////////////////// Vertex Program to Demonstrate Ambient Light//

varying vec3 normal, lightDir;

void main(){

gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;

}

Demo – Ambient Light Fragment Processor

//////////////////// Fragment Program for Ambient Light////

varying vec3 normal, lightDir;

void main(){float intensity=0.2;vec4 color= vec4(1.0,1.0,0.0,0.0);gl_FragColor = color*intensity;

}

Rasterizing Triangle using ShadersVertex Shader

void main() { gl_Position = ftransform();}

Triangle – Fragment Shaderuniform vec2 v0, v1, v2;

///////////////////////////////////////// 2D cross product;//float crs(const vec2 u, const vec2 v){ return u.x * v.y - u.y * v.x; }

/////////////////////////////////////// Main routine test whether screen pixel is // within the triangle// void main() { vec2 p = gl_FragCoord.xy; if (crs(v1 - v0, p - v0) >= 0 && crs(v2 - v1, p - v1) >= 0 && crs(v0 - v2, p - v2) >= 0) gl_FragColor = vec4(1.0,0.0,0.0,0.0); else gl_FragColor = vec4(0.5); // gl_FragColor = vec4(1.0,0.0,0.0,0.0); }

More Demos

GLSL Code snippets for doing various Lighting Models

GLSL demo from now defunct 3D Labs inc..

Turner Whitted and his Rendering Technique

Ray Tracing

Shooting a Ray from Eye into the scene ( for every pixel we need to do this )

It reverses the actual vision process to reduce the computational time..

We require robust computational primitives Ray Casting Demo Ray Tracing Demo A Discussion on POV Ray

Q & A

THANK YOU