Hello there, I just realised there is an entire forum dedicated to OpenGL so I guess this would be a good place to ask. Okay I have a problem. I am trying to steer and move a triangle I drew with the keyboard using the glRotate and glTransform functions. But I am having a problem moving the triangle on its own axis. I want the triangle to move in the direction it is facing. I figured all I would have to do is rotate it and then translate it and it would follow its own z axis (which I just rotated.) However, I can only get one of these to occur. When I translate and then rotate, the triangle will rotate around its own axis, but it will move down the origin''s z axis. When I rotate and then translate, the triangle rotates around the origin''s axis and moves down its own z axis. ahh! How can I have it rotate AND move on its own axis. Is there a better way? Any helps is greatly appreciated. - Jesse Barksdale

My problem is not limited to triangles... I also want to this with cubes, etc.. I just am not sure how to correctly move something like this.

thanks

Okay I just tried it with a cube. Same thing. I am not sure exactly what you suggested I do... sorry...

hmm...

darn...

I ran into a similar problem recently (during a graphics class)
was trying to move a robot around via arrow keys (basic stuff, I know.. but I''m new)

Anyways, I transformed using translate/rotate, but translated to a cosine/sine function of the rotated angle - the net effect is the translation still ''happens'' in worldspace, but *appears* to happen relative to the object in question.

glTranslatef(bot_x,7.5,bot_z);
// Robot''s center is at worldspace (0, 7.5, 0)
glRotatef(bot_th, 0,1,0);
// this is the frame of reference for the robot as a whole

where bot_x, bot_z, and bot_th are globals, (bot_x and bot_z are floats, and bot_th is an int (in degrees)) handling the obvious - then to move the robot ''forward'' I used the transformation

bot_x = bot_x + sin(bot_th*d2r);
bot_z = bot_z + cos(bot_th*d2r);

where d2r is a constant (degrees to radians - pi/180)

and to rotate the robot, simply

bot_th = bot_th + 5;

Obviously not optimal, but it does work, and should be a decent starting point.

I''''m a man with a one-track mind/
So much to do in one lifetime

Kam