vault backup: 2023-03-30 13:34:09

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Jet Hughes 2023-03-30 13:34:09 +13:00
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commit 1a639253c0

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@ -37,4 +37,37 @@ PERSPECTIVE PROJECTION
- The pinhole camera
- A simple, but useful, model
- There is a central point of projection (the pinhole, often a lens in reality)
- Light travels from the world, through the pinhole, to the image plane
- Light travels from the world, through the pinhole, to the image plane
> [!INFO] need a hole that is big enough to get enough light
> but small enough to create a sharp image
> light goes through the hole to the image plane
> pin hole is also the "lens"
THE PINHOLE CAMERA MODEL
![pin hole top view|300](https://i.imgur.com/bTSLvWR.png)
![pin hole diagam|300](https://i.imgur.com/TfclYHD.png)
> [!INFO] use negative of f as it is behind the pinhole
> find U using similar triangles rule
![|300](https://i.imgur.com/paeALF6.png)
> [!INFO] now we can project a point from 3d to 2d
> z is multiplies by 1 in the matrix so that the 3rd point of the homogenous coord becomes the z value
- We can put the image plane in front of the pinhole
- Removes the sign change
- Not practical for real cameras
- The maths works out just fine
![|200](https://i.imgur.com/hxPFHET.png)
![|100](https://i.imgur.com/KEiY1bf.png)
> [!INFO] cant really convert from 2d back to 3d without knowing focal length and z coord of every point
TRANSFORMING CAMERAS
INTRINSICS AND EXTRINSICS
- Often break this down into
![](https://i.imgur.com/3eENBA4.png)
- Most simple case:
- : camera calibration or intrinsics
- : camera pose or extrinsics