CNCapps

02-28-2006, 08:25 AM

Could someone please clarify how OpenGL supports the gltranslate etc commands by explaining the following:

My program creates arcs on say the XY_PLANE at constant Z coordinates based on a centre position of X0 Y0 Z0 and then translates the centre point to a given X/Y/Z point.

The program structure is as follows, please ignore syntax:

call arc(10,0,0)

call arc(10,0,0)

Public sub arc(x,y,z)

gltranslate x, y, z

glBegin GL_LINES

"arc definition as lines at centre 0,0,0 and fixed radius"

glEnd

End sub

I would expect the two arcs to be drawn in the same place at X10,Y0,Z0 but they appear to be at X10,Y0,Z0 and X20,Y0,Z0

I had expected the matrix to take the transformation as absolute values, this does not appear to be the case. Thanks for any assistance.

My program creates arcs on say the XY_PLANE at constant Z coordinates based on a centre position of X0 Y0 Z0 and then translates the centre point to a given X/Y/Z point.

The program structure is as follows, please ignore syntax:

call arc(10,0,0)

call arc(10,0,0)

Public sub arc(x,y,z)

gltranslate x, y, z

glBegin GL_LINES

"arc definition as lines at centre 0,0,0 and fixed radius"

glEnd

End sub

I would expect the two arcs to be drawn in the same place at X10,Y0,Z0 but they appear to be at X10,Y0,Z0 and X20,Y0,Z0

I had expected the matrix to take the transformation as absolute values, this does not appear to be the case. Thanks for any assistance.