Thanks.
I guess my question would then be how do I convert from x,y,z to a,b,c using maths instead of glTranslatef/glRotatef?
Cheers
Astan

Zack Schilling wrote:
You cannot modify the matrix between glBegin and glEnd calls, so no
translation or rotation between plotting of vertices is allowed.

If I understand what you want, you're trying to draw a line from the
"camera" to an object. Depending on how your frustum is set up, this
may be a bad idea. In any case, it'll look strange and glitchy at
best. But if you insist, here's what you need to do.

the identity and doing any drawing, perform a glTranslatef(-x,-y,-z)
as well as any other "camera" rotations you want. Once that's done,
plot a line from (x,y,z) to (x1,y1,z1), where (x1,y1,z1) are the
coordinates to the object you're drawing the line to.

glBegin(GL_LINES)
glVertex3f(x,y,z)
glVertex3f(x1,y1,z1)
glEnd()

You cannot and should not try to adjust the matrix while plotting
points.

-Zack

On Jul 2, 2009, at 10:51 PM, Astan Chee wrote:

Hi,
I'm trying to draw a line between two points (x0,y0,z0 and x1,y1,z1)
like this:

glPushMatrix()

glEnable(GL_BLEND)

glTranslatef(x,y,z)

glRotatef(-angle[0],0,1,0)
glRotatef(angle[1],1,0,0)

glColor4f( 1, 0.0, 0.0, .8 )

glBegin(GL_LINES)
glVertex3f(x0,y0,z0)

glTranslatef(-x,-y,-z)

glRotatef(angle[0],0,1,0)
glRotatef(-angle[1],1,0,0)

glVertex3f(x1,y1,z1)
glEnd()

glDisable(GL_BLEND)
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)
glPopMatrix()

Where x0,y0,z0 is the point near or in front of the "camera" and the
point x1,y1,z1 is the point in "real world coordinates".
This doesn't seem to work. How should I be doing this assuming I don't
know how to calculate either point in terms of the other?
Thanks
Astan

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