Jump to content
  • Advertisement
Sign in to follow this  
riyunoa

Question about OpenGL positioning

This topic is 4846 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

If you intended to correct an error in the post then please contact us.

Recommended Posts

Advertisement
You're actually changing the center of your coordinate system (or performing a translation on your World Transform, if you prefere).

As such it just means that all coordinates will be offset by (x, y, z).

So

glTranslatef(100, 0, 00);
glBegin(GL_LINES)
glVertex3f(10, 10, 10)
glVertex3f(-10, -10, -10)
glEnd();

would give an equivalent image to

glBegin(GL_LINES)
glVertex3f(110, 10, 10)
glVertex3f(90, -10, -10)
glEnd();

Makes sense?

[edited for errata]

[Edited by - __ODIN__ on September 5, 2005 11:57:55 PM]

Share this post


Link to post
Share on other sites
You do not move objects but, like __ODIN__ says, the coordinate system tied to the object. There is no top left or middle of objects, you just send vertices and whereever they end up on screen will depend on the viewport, projection and modelview you have specified.

So, if you translate you move the origin of the local coordinate system, and then you draw the object into that moved/translated coordinate system by sending the vertices. Whereever the corner or middle of the object you paint end up depends on the vertices you specify: (0, 0, 0) would obviously be the middle of a rectangle if you draw a rectangle from (-10, -10, 0) to (10, 10, 0); but you may also draw it from (0, 0, 0) to (20, 20, 0) and then the origin of the local coordinate system would be one of the corners.

[Edited by - brulle on September 6, 2005 7:20:50 AM]

Share this post


Link to post
Share on other sites
Sign in to follow this  

  • Advertisement
×

Important Information

By using GameDev.net, you agree to our community Guidelines, Terms of Use, and Privacy Policy.

GameDev.net is your game development community. Create an account for your GameDev Portfolio and participate in the largest developer community in the games industry.

Sign me up!