Visual Plane
every picture states the point it is correct from
Series

Clipping — the series

2 essays on one idea, from the one that introduces it to the one that assumes the rest.
  1. clipped at the near planedivided without clippingdirection cosine -1.0000 — the far end is drawn 2142 px away20 grid segments, 2.4 m of them behind the eyea reversed line is not a large error, it is a different picture

    What happens behind the eye

    A point behind the camera has a perfectly plausible image. Dividing by a negative fourth coordinate flips both signs, so the point lands through the principal point on the far side of the frame, and a segment crossing the eye plane is drawn straight, inside the frame, and running in exactly the opposite direction — a direction cosine of −1.0000.

    part 1 · pipeline
  2. 24 kept · 26 clipped · every mark unmovedcorrect from 17 cm, at 160 mm wideclip plane tilted 18°

    The near plane can be any plane

    Rewrite one row of a projection matrix and the near plane stops being perpendicular to the axis and becomes whatever plane is asked for. Every x and every y is untouched — it is the same projection of the same scene from the same eye — and the depth order is wrecked, which is a clean separation of the two things a projection matrix does.

    part 2 · pipeline

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