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### #ActualNik02

Posted 14 October 2012 - 10:31 AM

Perspective projection is (at its core) simply dividing the x and y by the (z * field of view), so that the further away something is, the smaller it looks. Practical implementations in computer graphics also map the desired scene depth range to the range of the viewport (typically 0...1) to accommodate the discrete range of a depth buffer and to establish a frame of reference for the depth in general.

Orthogonal projection, by contrast, is usually a combination of linear scaling and translation, with no correlation between the depth of the geometry and its scale.

If you need projection like that from a spotlight, then you need perspective projection as opposed to orthogonal. Orthogonal projection would suit a (pseudo)infinitely far away light source, like the sun as seen from earth, though.

### #4Nik02

Posted 14 October 2012 - 10:15 AM

Perspective projection is (at its core) simply dividing the x and y by the (z * field of view), so that the further away something is, the smaller it looks. Practical implementations in computer graphics also map the desired scene depth range to the range of the viewport (typically 0...1) to accommodate the discrete range of a depth buffer and to establish a frame of reference for the depth in general.

Orthogonal projection, by contrast, is usually a combination of linear scaling and translation, with no correlation between the depth of the geometry and its scale.

If you need projection like that from a spotlight, then you need perspective projection as opposed to orthogonal. Orthogonal projection would suit a (pseudo)infinite light source, like the sun as seen from earth, though.

### #3Nik02

Posted 14 October 2012 - 10:14 AM

Perspective projection is (at its core) simply dividing the x and y by the z, so that the further away something is, the smaller it looks. Practical implementations in computer graphics also map the desired scene depth range to the range of the viewport (typically 0...1) to accommodate the discrete range of a depth buffer and to establish a frame of reference for the depth in general.

Orthogonal projection, by contrast, is usually a combination of linear scaling and translation, with no correlation between the depth of the geometry and its scale.

If you need projection like that from a spotlight, then you need perspective projection as opposed to orthogonal. Orthogonal projection would suit a (pseudo)infinite light source, like the sun as seen from earth, though.

### #2Nik02

Posted 14 October 2012 - 10:13 AM

Perspective projection is (at its core) simply dividing the x and y by the z, so that the further away something is, the smaller it looks. Practical implementations in computer graphics also map the desired scene depth range to the range of the viewport (typically 0...1) to accommodate the discrete range of a depth buffer and to establish a frame of reference for the depth in general.

Orthogonal projection, by contrast, is usually a combination of linear scaling and translation, with no correlation to the depth of the geometry and its scale.

If you need projection like that from a spotlight, then you need perspective projection as opposed to orthogonal. Orthogonal projection would suit a (pseudo)infinite light source, like the sun as seen from earth, though.

### #1Nik02

Posted 14 October 2012 - 10:12 AM

Perspective projection is (at its core) simply dividing the x and y by the z, so that the further away something is, the smaller it looks. Practical implementations in computer graphics also map the desired scene depth range to the range of the viewport (typically 0...1) to accommodate the discrete range of a depth buffer.

Orthogonal projection, by contrast, is usually a combination of linear scaling and translation, with no correlation to the depth of the geometry and its scale.

If you need projection like that from a spotlight, then you need perspective projection as opposed to orthogonal. Orthogonal projection would suit a (pseudo)infinite light source, like the sun as seen from earth, though.

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