There are three ways to get measurments of a triangle: sine, cosine, and tangent. Each are methodical to SOHCAHTOA, meaning:

sine = opposite over hypotenuse
cosine= adjacent over hypotenuse
tangent = opposite over adjacent

You need to know these because when you turn left, for example, you would decrement a variable ''float angle''. Then, you need to figure out whether the sin, cos, or tangent is needed.

In the case of turning, the most commonly used are the negative cosine and the sine.

gluLookAt takes 9 arguments. The first three are the camera position (x,y,z), which are unaffected when you turn. The ones that are affected are the next three arguments, (lx, ly, lz) which are the look-x, look-y, and look-z. They determine the point where the camera is looking.

So when you move forward, you need to figure out what angle measurement between you and the z axis (and x axis) is so that you can move in the proper direction.

The mathematical (actually, it''s geometrical) way of calculating this properly is in the functions that I gave you.

Set up a system of BOOLs. Like this:

bool turnleft; bool turnright; bool forward; bool backward;

Then, (assuming that you are using GLUT), set up your keyboard up functions and keyboard down functions.


float turnangle;

void main(int argc, char **argv){
...
glutKeyboardUpFunc(KeysUp);
glutKeyboardFunc(KeysDown);
...
glutDisplayFunc(RenderScene);
...
glutMainLoop();
}

void KeysDown(unsigned char key, int x, int y){
switch(key){
case ''a'': turnleft=1; break;
case ''d'': turnright=1; break;
case ''w'': forward=1; break;
case ''s'': backward=1; break;
default: break;
}
}

void KeysUp(unsigned char key, int x, int y){
switch(key){
case ''a'': turnleft=0; break;
case ''d'': turnright=0; break;
case ''w'': forward=0; break;
case ''s'': backward=0; break;
default: break;
}
}

void RenderScene(void){
glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
...
if(turnleft){
turnangle-=0.01;
moveLeftandRight(angle);
}
if(turnright){
turnangle+=0.01;
moveLeftanfRight(angle);
}
if(forward){
moveForwardandBackward(1);
}
if(backward){
moveForwardandBackward(-1);
}


Get it now? Geometry is the only way you can interpret the angles easily. Because the default setting for translating forward would be along the z axis, you not only need to compenstate your lx,ly,lz coords by translating along the z axis, but also the x axis.

This, my friend, is why geometry is critical.

~Jesse Lawson,
www.proggin.com/tutorials/opengl/index.htm

I just noticed that you aren''t using GLUT; I thought you would be. The functions are still cooperative, so try them before you deny them.

Do you know what sine, cosine, and tangent are? No?

Hmm... Look them up. To do what you want to do, the way you want to do it, you need to use SOHCAHTOA.

Do you know why?

Well, my examples involved incrementing an angle, right?

SOHCAHTOA was previously explained by me. Im serious, ask your math teacher about it, its hard to explain without visual contact. =)