Computer Science 385.3 Term 1, 2006 Tutorial 2 Assignment 3 – The Virtual World.

Computer Science 385.3

Term 1, 2006

Tutorial 2

Assignment 3 – The Virtual World


Some Assignment Requirements:

-Use of a cube to contain the world.-Interactive controls.-Use of the three-term lighting model.-Some extra geometry.-Some texture mapping.


World Cube

Your virtual world will be inside the World Cube, so make sure that the sides of the cube are pointing inwards – if the vertices are written counter-clockwise, you are looking at the front of the polygon.

Also, remember that you are required to use glFrustum(), not any of the utility routines such as gluPerspective, etc.

glFrustum(Left, Right, Bottom, Top, Near, Far);


Interactive Controls

-The user should be able to wander through your world freely using some key or mouse commands.

-You should use the ModelView matrix to accomplish this.

A series of rotatations and translations can be applied to the world in order to show the user's perspective.



Remember: The rotation and translation matrix multiplications are applied in reverse order.

GLfloat direction; // can be modified when user inputs commands.Vector position; // the user's position in the scene.

display (void){

...glPushMatrix();glLoadIdentity();glTranslatef(position.x, position.y, position.z);glRotatef(direction,0,1,0); // Rotation should go after renderScene(); // translation!glPopMatrix();...

}



The multiplication matrix used on the ModelView is similar to a stack – hence, the glPushMatrix() and glPopMatrix() commands.

These can be used to save and load a previous matrix, which is very useful when you only want to transform specific parts of the scene (such as a spotlight moving through the scene.)

void handleKeystroke(int key, int x, int y){ if (key == GLUT_KEY_LEFT) {

… }}

Arrow keys can be captured using:


3-Term Lighting Model

Lightpoint = Ambientpoint + Diffusepoint + Specularpoint

OpenGL does these calculations for you, if you set up the lighting properly.

To use OpenGL lighting, the programmer is expected to define:

-Surface normals (normalized).

-Material properties.

-Light information.


3-Term Lighting Model

Each light can have:

-Position in the world

-Ambient, diffuse and specular components.

-Direction and spotlight variables.

-Attenuation variables – best made small in OpenGL.

glEnable(GL_LIGHTING);glShadeModel(GL_SMOOTH);glEnable(GL_LIGHT1);

Setting up the lighting:


Texture Mapping

Can add precious detail to flat polygons.

Can simulate some aspects of complicated geometry without the cost.

Must have a texture to map.

Must load texture into the program.

Must provide a mapping between texture coordinates and surface coordinates – trivial for square shapes.


Texture Mapping

Setting up the textures for mapping:

glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glEnable(GL_TEXTURE_2D);

glTexImage2D(GL_TEXTURE_2D, 0, 0, dimension, dimension, 0, GL_BGR_EXT, GL_UNSIGNED_BYTE, x); glBegin(GL_POLYGON); glTexCoord2f( 0, 0 ); glVertex3f( -50, -50, -50 ); glTexCoord2f( 1, 0 ); glVertex3f( 50, -50, -50 ); glTexCoord2f( 1, 1 ); glVertex3f( 50, 50, -50 ); glTexCoord2f( 0, 1 ); glVertex3f( -50, 50, -50 ); glEnd();

Texture Mapping:

Questions?

Computer Science 385.3 Term 1, 2006 Tutorial 2 Assignment 3 – The Virtual World.

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