how to rotate like earth?

Hi,

Im trying to one thing thats too difficult …
how to rotate like earth … i dont want to know a rotate in axis …
for example … when we talk about graphs you can see what im talking about

imagine an axis x with minimum 0 and maximum 5 … if we do a half-rotate 5 will become -5.
i dont want this, i want 0 in the position of 5 and 5 in the position of 0.

thanks

I did not understood a word :stuck_out_tongue:
Well I will try to be creative and interpret your title. Do you want something like :

glloadidentity;
rotate X axis (an horizotal one) to 23.45° to reflect the earth axial tilt;
rotate Y axis (the vertical one) to a value depenting on the time linearly (ie 24 hours for 360°);
draw earth;

hrrmm . not that …

look this image i did … there is a diff between both when you rotate 180 degrees.

I know how to do the first … but i want the second.

thanks

Ahhhh much clearer !

So the initial triangle has its bottom left vertex aligned on yx (0;0). You just have to shift it a bit.

  1. may be done like this :
    glPushMatrix();
    <draw triangle>
    glRotate(180, 0,0,1);
    <draw triangle>
    glPopMatrix();

  2. may be done like this :
    glPushMatrix();
    glTranslate2f(-1.0f,0.0f); // if the triangle is about 2 in width. Else adjust for your setup.
    <draw triangle>
    glPopMatrix();
    glPushMatrix();
    glRotate(180, 0,0,1);
    glTranslate2f(-1.0f,0.0f); // if the triangle is about 2 in width. Else adjust for your setup.
    <draw triangle>
    glPopMatrix();

Untested, but should not be too far from the truth.