global coordinates

OpenGL OpenGL: Basic Coding
1

How do I get a vertex’s global coordinates after I do severl PushMatrix/translate,multmatrix,scale, etc.

for example (psudocode)

glLoadIdentity
glPushmatrix
gltranslate
glrotate

glPushMatrix
glscale
glMultMatrix

glVertex3f X, Y, Z

glPopmatrix
glPopMatrix

how do I get X,Y, and Z where they would appear in global coordinates?

2

If you’re interested in performance, then shadow all those matrix calls into your own data structure. Then, you multiply your vertex position by them. Problem solved.

3

Hmm… I was hoping for something simpler, but I suppose I could do that, since most of my translation and transformation code is done with MultMatrix anyway. Time to brush up on my matrix multiplication skilz.

4

Ok, so once I have the modelview matrix, how do I use that to translate the local coordinates back into global coordinates?