# glRotate

Hi. I’m new to OpenGL and I have a problem.
I’m trying to rotate an object about the axis using glRotatef(…). The code is something like this:

if(x< 180)
glRotatef(10, 1.f, 0.f, 0.f);

For some reason, the object moves in the direction of positive x everytime the image is redrawn. I would prefer the object to stay stationary rather than move. Can someone give me why this is happening?

Do you want it to rotate constantly?

if so, try:
add an int called “rvar” for Rotation angle variable

glRotatef(rvar, X,Y,Z); //Enable the XYZ sxis by giving them a value of 1. Or else leave as “0”
then at the end of the function:
rvar+=0.3f; //Add 0.3 to the angle for each loop.

so:

while(rvar < 120)
{
glRotatef(rvar,1.0,0.0,0.0);
/* Do Junk */
rvar+=0.03; //You can change of course
}

As for why it moves left, I dunno, is that ALL the code? show wha you have put prior, and define your ints.

[This message has been edited by ThinIce (edited 01-31-2002).]

Before or after glRotate are you using gltranslate of glscale?

Also the object you are drawing, is the point (0,0,0) in the center of the object or at a edge? You must remember that rotate moves the object around its axis.
If the axis is a corner of your object, then the object rotate from that point.

Let us see how you have drawn your object?

The base of the object is at (0,0,0). The top coordinate is roughly (0,0,70). I tried rotatating about the x-axis, and the object appeared to be moving in the direction of positive x while it rotated. I managed to fix it. The program reads in the coordinates from a file. The program which generates the coordinates was using a different coordinate system (which I didn’t know). So (0,0,0) in the file’s coorinates didn’t map to (0,0,0) in my coordinates. So that’s what was causing the problem.

I appreciate everyones contributions.