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every picture states the point it is correct from
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Eightpoint — the series

2 essays on one idea, from the one that introduces it to the one that assumes the rest.
  1. 0.5120.1110100how finely each point is read off the picture (px, log scale)worst epipolar error against the exact geometry (px, log scale)raw pixelscentred and scaled1.1× apart at 0.25 px, 29.9× at 4 pxspread 102 against 2.5e+5

    Eight points and the basis they are read in

    The linear system that recovers a fundamental matrix is written in whatever coordinates the marks were read in, and pixel coordinates are a bad choice. Centring and scaling them first is worth nothing at a quarter-pixel reading and a factor of thirty at four.

    part 2 · twoviews
  2. -2e-7-1e-70-0.800-0.700-0.600-0.500α, the mix of the two nullspace directionsthe determinant that a fundamental matrix must make zeroa cubic with three real roots3 matrices, all exact

    Seven marks, three answers

    Seven correspondences leave a two-dimensional nullspace, and the requirement that a fundamental matrix be singular is a cubic in the mix — one or three real roots. Here it has three, and all three satisfy every one of the seven marks to 8.9 × 10⁻⁹ pixels. The eighth mark, withheld, separates them by more than an order of magnitude.

    part 3 · twoviews

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