I know blender can display both orthographic and perspective projection. But, when we look at a cube in blender's viewport, I'm unable to distinguish by eye, if the projection in the viewport is a one-point, a two-point or a three-point perspective. What does blender use, and is this something changeable?
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1$\begingroup$ Isn't the distinction between one-, two- and threepoint perspective just for drawing? Dependent on the camera position, the 3D to 2D perspective projection will give you any of the three... $\endgroup$ – haarigertroll Jul 13 at 11:20
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$\begingroup$ @haarigertroll , um... blender is basically drawing to the viewport, and the math seems to be different: people.eecs.berkeley.edu/~barsky/perspective.html $\endgroup$ – juztcode Jul 13 at 11:22
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1$\begingroup$ It's been a while since I had to calculate transformation matrices, but I think that the math is essentially the same, with just a different series of transformations. Take a look at these (same camera parameters, just different position gives you one, two or three vanishing points) i.stack.imgur.com/JKEx1.png i.stack.imgur.com/MZfTe.jpg i.stack.imgur.com/2PLcI.jpg $\endgroup$ – haarigertroll Jul 13 at 11:30
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2$\begingroup$ Addendum: It actually says so on your linked website (last paragraph): "Then the matrix for this 3-point perspective is: [...] And, the 1 point and 2 point perspective matrices are special cases with 1/dx and/or 1/dy equal to zero." $\endgroup$ – haarigertroll Jul 13 at 11:30
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I'm no architect, but this should only depend on your camera alignment.
- 1 point perspective - camera aligned to 2 axis
- 2 point perspective - camera aligned to 1 axis
- 3 point perspective - camera not aligned to any axis
As given in the link in the comment and mentioned by @haarigertroll mathematically these are special cases of the one point perspective.
answered Jul 13 at 11:48
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3$\begingroup$ Dang! Beat me to it... and nicely illustrated. :) $\endgroup$ – Robin Betts Jul 13 at 12:11
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