glRotate

OpenGL OpenGL: Basic Coding
1

I used glRotatef(0.0f,0.0f,45.0f).
I am getting clockwise rotation instead of counterclockwise.How??

2

With that call, your program shouldn’t even compile. You are only passing three parameters, while glRotatef requires four.

3

First you are using the function wrong:

glRotatef(angle, X, Y, Z);

Where angle is rotation in degrees.
X Y Z = 1 for rotate axis or 0 for no rotation.

To rotate only the X axis then the function would look like this:
glRotatef( 45.0, 1.0, 0.0, 0.0) // rotate X by 45
glRotatef( 15.0, 0.0, 1.0, 0.0) // rotate Y by 15

Originally posted by azariah:
I used glRotatef(0.0f,0.0f,45.0f).
I am getting clockwise rotation instead of counterclockwise.How??

4

woops! I typed wrongly.Sorry…
Actually I used glRotatef(45.0f,0.0f,0.0f,1.0f)
But I am getting clockwise rotation instead of counterclockwise.How?

[This message has been edited by azariah (edited 03-18-2002).]

[This message has been edited by azariah (edited 03-18-2002).]

5

maybe because your angle is positive? use ‘-45.0f’

6

Originally posted by azariah:
woops! I typed wrongly.Sorry…
Actually I used glRotatef(45.0f,0.0f,0.0f,1.0f)
But I am getting clockwise rotation instead of counterclockwise.How?

It could be the location of the camera — glRotatef(45,0,0,1) rotates CCW around +Z.

For example, with gluLookAt(0,0,-1, 0,0,0, 0,1,0) it would rotate clockwise.

7

I tried with
glRotatef(45,0,0,1);
gluLookAt(0,0,1, 0,0,0, 0,1,0);

Still I am getting clockwise rotation about +z axis.Where am i going wrong???

8

Ever thought of rotating around -z (i.e. glRotatef(45.0f, 0.0f, 0.0f, -1.0f). Changing the sign is the same as changing the direction of rotation.

9

I am using the following code …

void RenderScene(void)
{
glClear(GL_COLOR_BUFFER_BIT);

glMatrixMode(GL_MODELVIEW);
glLoadIdentity();

gluLookAt(0.0f,0.0f,1.0f,0.0f,0.0f,0.0f,0.0f,1.0f,0.0f);

glColor3f(1.0f,0.0f,0.0f);
glutSolidSphere(10.0f,15,15);

glColor3f(1.0f,1.0f,0.0f);
glRotatef(45.0f,0.0f,0.0f,1.0f);
glTranslatef(50.0f,0.0f,0.0f);
glutSolidSphere(10.f,15,15);

glutSwapBuffers();
}

Here the coordinate system is rotated in clockwise direction.
It should be in counter clockwise direction.
Where am I going wrong here???

[This message has been edited by azariah (edited 04-02-2002).]