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OpenGL OPEN GL Unit Length

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Absolutely not. OpenGL units are, like any other API, completely arbritary.

They can be anything you want.

In 3d, the appearance is controlled by the view matrix set up with gluPerspective etc.

If you are setting up an orthogonal projection, glOrtho allows you to choose the bottom left and top right coordinates. If these happen to coincide with pixels, then you'll have 1.0 = 1 pixel (Assuming you did a glLoadIdentity on the projection matrix beforehand).

I think the absolutely default (orthogonal) projection matrix makes the screen** go from 0,0 to 1,1 (bottom left / top right). But I'm not sure as I never use it.


** By "screen" I mean, "the bounds of the visible area of the opengl context" which may or may not mean screen depending on how the context was created (for example, it could be an offscreen context or a context in a window which only covers part of the screen)

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