[Gambas-user] gb3: OpenGL Rotate and Translate logic

[tommyline at ...2340...]

A quote from NeHe tutorial:

"We push the matrix (which basically saves the position of everything on the screen) and use glScalef(1.0f,-1.0f,1.0f) to flip the object upside down (creating a real looking reflection). Setting the y value of glScalef({x},{y},{z}) to a negative value forces OpenGL to render opposite on the y-axis. It's almost like flipping the entire screen upside down. When position an object at a positive value on the y-axis, it will appear at the bottom of the screen instead of at the top. When you rotate an object towards yourself, it will rotate away from you. Everything will be mirrored on the y-axis until you pop the matrix or set the y value back to 1.0f instead of -1.0f using glScalef({x},{y},{z})"

Maybe it could help you understand what and why is happening there. 

Tomek

I'll be damned. I think I got it. Looks like applying a certain scale 
transformation to the projection matrix does it:

   Gl.MatrixMode(Gl.PROJECTION)
   Gl.LoadIdentity()
   Glu.Perspective(45, sWidth / sHeight, -1, 1)
   Gl.Scalef(1, -1, 1)

Thanks for all your help. Hopefully I can move forward with this under 
my own power and not have to bother the list again for a while.

-- 
Kevin Fishburne
Eight Virtues
www: http://sales.eightvirtues.com
e-mail: sales at ...1887...
phone: (770) 853-6271


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