What’s the plan for today?
Go over our framework code.
Learn some basic OpenGL!
Reveal Lab 1
Answer questions
Framework Environment
C/C++ and OpenGL
Code will be given with Makefiles
You can compile in Linux, Mac, and Windows!
You must use the framework
What should you know?
At the very least
You’ve programmed before
You know the programming cycle
Better for you if
You are familiar with C/C++
Amazing if
You already know OpenGL
Have a degree in Computer Science
Framework
Where do I get it?!
Resources in Class Website
This lab’s framework provides you with
An initial OpenGL window
Callback functions you will need
What is OpenGL?
A powerful, open source graphics library
Widely used in both industry and academia
Capable of rendering 3D geometries with a
plethora of effects
Keeps a “global” state
Transformation, projection matrices
Attributes from primitives
Exercise: Compiling
Compile the framework
Change window size, position, and title
Exercise: Drawing Things!
Since you guys are now pros, let’s draw things!
Every GL primitive starts with glBegin(…), and ends
with glEnd ()
Example:
glBegin (GL_POINT);
glVertex3f( 1.0,1.0,1.0);
glEnd()
Exercise: Drawing Quads
Find the DrawGLScene() function
After glLoadIdentity(), create a GL primitive
using GL_QUADS
Exercise: Drawing Quads
Add this code
And this code…
What just happened?!
OK, that’s weird, why is the screen yellow?
We’ve basically rendered our object too close
for us to really see it. So, we need to move (or
translate) it further back.
Translation and Rotation
Rotation (unsurprisingly) rotates the primitive,
BUT rotates it around the “world” axis, NOT its
local axis
Hint: You can think of the camera as always being at the
world origin(0,0,0)
Translation “moves” the primitive around to a
different location
The order you do translations and rotations in
MATTERS
Translation and Rotation
Rotate
Translate
Translation and Rotation
Rotate then Translate
Translate then Rotate
Translation and Rotation
WARNING!!!
OpenGL will perform translations and rotations IN THE
OPPOSITE ORDER YOU WRITE THEM IN CODE
i.e. writing the following in code:
…
glTranslate(...)
glRotate(…)
…
Will rotate then translate the primitive
Translation and Rotation
Important things to keep in mind:
Translate/Rotate operates relative to the world
origin
The order of translations and rotations matters
OpenGL will perform translations and rotations in
the OPPOSITE order you list them in code
Exercise: Finish the cube
Add this line of code above your primitive in your
drawing function.
Finish the rest of the cube.
Change the color of each side to something else!
glColor3f( red, green, blue );
Callbacks
GLUT allows us to interface between events
(such as clicking, keyboard input, etc.) and
OpenGL.
Lab 1
Implement a camera to move around in OpenGL.
Use the callback functions provided for you.
Use the cube as a way to debug your camera.
Make sure you at least create a vector, camera,
and framework class.
Questions?
Useful sites
OpenGL Reference Pages:
http://www.opengl.org/sdk/docs/man/ (what we use)
http://www.opengl.org/sdk/docs/man4/ (latest ver.)
NeHe Tutorials (under Legacy Tutorials):
http://nehe.gamedev.net/
Note: As of Aug. 2011, the current tutorials are a little
out-of-date/deprecated, but in the process of being
updated. They still give a good explanation of the
basics, but don’t expect to be able to run the code.