I am fresh out of beginners programming (game maker) and I need some help with opengl's projection system. What I need is a camera that has movement and direction to it, not a camera that sits and has the world move around it. What type of projection should I use gluPerspective or the other one. What would I have to use to get a simple movement system setup. Would it have anything to do with gluLookAt? I am I bit lost and kind find many answers on my own. Some help would go a long way. Edit: Ok currently I am using gluPerspective(45,width/height,1,100000). Thats about all I could figure out, well that and how to get the world to move around it using glTranslate. Now I need to leave how to keep the world in one set location and move the camera around. Does anyone have any idea how this can be done? [Edited by - snowfell on May 10, 2008 11:36:34 AM]

Well I understand that projection draws everything on a hor and vert axis (y being vert, x and z being hor). Now what I don't understand is how to get motion and direction out of the camera. So far I have been able to make a weak 3d engine using glut. I have been able to render a simple floor and and put colored markers at each corner.

So this is the bare bone engine I wiped together:

void projection(int width, int height)
{
glViewport(0,0,width,height);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45.0f,width/height,1.0f,10000.0f);
gluLookAt(cord_x,cord_y+5,cord_z,0.0,0.0,dir,0.0,zdir,0.0);
}

void display()
{
float room_width=255;
float room_height=255;

glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();

glBegin(GL_POLYGON);
glColor3d(.25,.25,.25);
glVertex3f(0,0,0); glVertex3f(room_width,0,0);
glVertex3f(room_width,0,room_height); glVertex3f(0,0,room_height);
glEnd();

//drawing...
}

Is their anything I can change to include a motion system? Or are there any improvement I could add to what I have done so far.

Quote:Original post by snowfell
void projection(int width, int height)
{
...
glMatrixMode(GL_PROJECTION);
...
gluLookAt(cord_x,cord_y+5,cord_z,0.0,0.0,dir,0.0,zdir,0.0);
}

You should not put the view matrix into the projection matrix. Instead, it should be put into model-view matrix.

Quote:Original post by MrPickle
If you have the view direction you can multiply that by a distance and add/subtract it to the current position to move in that direction.

If you don't have the view direction here's how to work it out:
*** Source Snippet Removed ***

Ok so where might I put this and its variables? I have seen codes very similar to this in my game making past. Another rather important question I have is where do most of the projection codes go, and why (In their own function or what)?

In OpenGL, you have three predefined matrices, i.e. model-view matrix, projection matrix and texture matrix.

Model-view matrix, as suggested by its name, is to handle model and viewing. Just for the naming reason, you should handle the viewing using model-view matrix. Besides, there are good some reasons behind why model and viewing get together. It is because both are usually translation and rotation only. Also, it is easier to make specular lighting correct... ...

Please read the following article,
http://www.sjbaker.org/steve/omniv/projection_abuse.html

Ok I was able to read through that page but it didn't really explain projection order well. I was just wondering what a effective 3d projection system might look like (as in where gluLookAt and other important codes should be place and how to be used). I have a simple engine going and so far I have a general outline to this, but I need some structure to improve it. If it would help I could post what I have done so far, but only if it could help get some answers.