1. UMBC GDC Programming Tutorial
Lesson 1
Understanding the basics of C++
Game Programming using OpenGL
(and GLUT)
This is geared toward getting your feet wet.
Not jumping in.

2. Overview Why you're here What you'll be using Background of C++
What's different
Getting started
Get a working demo
Add some code
Review

3. Why? Get a grasp on the way of thinking.
Understand what makes it different from normal programming.
Get experience with a graphics system.
Get a sort of hello world working.
To ask questions and interrupt me a lot.

4. Tool Set C++ Most game programming is still done in C++
Basic code is very similar to other high level languages
OpenGL
Works everywhere (Except XBOX 360)
Exposes more of the background
GLUT + cppgpgpu
Get moving - fast.

5. C/C++ Background You #include definitions You write functions
You call functions from main
You exit

6. Traditional C/C++ Program
#include <stdio.h>
int AddTwoNumbers( int a, int b ) {
return a + b; }
int main()
printf( “3 + 4 = %d\n”,
AddTwoNumbers( a, b );
return 0;

7. C++ Classes Allow a level of abstraction, enabling:
Appearance as objects
Classful function members
Classful data members

8. C/C++ Function Pointers
Allows you to call a function dynamically
Like any other pointer, but dereferences into call

9. What's Different? #include <stdio.h>
int AddTwoNumbers( int a, int b ) {
return a + b; }
int main()
printf( “3 + 4 = %d\n”,
AddTwoNumbers( a, b );
return 0;

10. So... Programming in larger systems requires a leap of faith
You are generally not in control of the main loop
You must follow certain standards depending on your framework
Code no longer remains linear

11. The Difference Start A B A Some kind of crazy engine sort of thing B

12. This Thing
MyDraw
main()
GLUT
Start
Simple, huh?

13. Getting Started Make sure to open main.c in the main folder.
We will be going through the code in the order it appears
Stuff in Orange Boxes is pertinent to lesson.

14. main.cpp overview (1) #include "GLUTCore.h" #include "OGLParts.h"
#include <stdio.h>
void MyDraw();
Texture T1;
Inclusion of Definitions
Definition of Texture Object
Function Prototype

15. main.cpp overview (2) int main (int argc, char * const argv[]) {
Function Definition
int main (int argc, char * const argv[]) {
printf("Hello, World!\n");
//This must be set before init.
GLUT.SetDrawFunct( MyDraw );
GLUT.Init( argc, (char**)argv, 640,
480, "Hello World" );
//Enable Depth
glEnable(GL_DEPTH_TEST);
Debugging
Set up Variables
Initialize System
Set Up Environment

16. (Note: All of this code only gets executed once)
main.cpp overview (3)
//Load a texture from a file
T1.LoadTextureFile( "Basic.ppm" );
GLUT.DrawAndDoMainLoop();
return 0; }
Give up control
Load an Image
(Note: All of this code only gets executed once)
Clean exit back to OS

17. main.cpp overview (4) void MyDraw() { //Clear the screen.
glClearColor( .1f, .1f, .2f, 0.0f );
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
T1.ActivateTexture( 0 );
DrawSquare();
T1.DeactivateTexture( 0 );
Set up Rendering States
Perform Render Action (Clear Screen)
Perform Render Action (Draw Quad)

18. main.cpp overview (5) //Update FPS, print if its time. GLUT.TackFPS();
Tell system to perform function
//Update FPS, print if its time.
GLUT.TackFPS();
//You need these last two lines.
glutSwapBuffers();
glutPostRedisplay(); }
Swap front buffer with back buffer
(cue to self: talk about double-buffering)
Tell system to redraw at its own leisure

19. Let's add some code Modify the MyDraw() function.
Replace call to Enable/Disable Texture and DrawSquare(); with our own code
Draw a single triangle in immediate mode

20. Added code T1.ActivateTexture( 0 ); DrawSquare();
Change Render State
T1.ActivateTexture( 0 );
DrawSquare();
glBegin( GL_TRIANGLES );
glColor3f ( 1.0, 0.0, 0.0 );
glVertex3f( 0.0, 1.0, 0.0 );
glColor3f ( 0.0, 1.0, 0.0 );
glVertex3f( 1.0, 0.0, 0.0 );
glColor3f ( 0.0, 0.0, 1.0 );
glVertex3f( 0.0, 0.0, 0.0 );
glEnd();
T1.DeactivateTexture( 0 );
Vertex Attribute
(R,G,B)
Vertex Location
(X,Y,Z)

21. Review Understand the difference from this and traditional programming
Have a basic understanding of this new type of program flow
Have a working shape on your screen

22. Questions (last chance)
You know, I feel really bad about putting this image here, since I can't seem to find where it came from. The original source did not credit it.