OpenGL Transformations

Rotation

glRotatef(GLfloat angle, GLfloat x, GLfloat y, GLfloat z)

Rotates objects around the axis (x, y, z), by angle degrees.

In 2D, use 0, 0, 1 as the axis.



OpenGL rotations are right-handed - a positive angle rotates counter-clockwise (in 2D).



Rotations are based around the current origin, which might not be the center of the object being drawn. 

glBegin(GL_TRIANGLES)
glVertex2f(0.5, 0.0)
glVertex2f(0.8, 0.0)
glVertex2f(0.65, 0.5)
glEnd()

glRotatef(90.0, 0.0, 0.0, 1.0)
glBegin(GL_TRIANGLES)
glVertex2f(0.5, 0.0)
glVertex2f(0.8, 0.0)
glVertex2f(0.65, 0.5)
glEnd()

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