Clipping

Cohen-Sutherland Outcodes

Encode which side of a clipping rectangle each segment endpoint lies on.

Example

Encode which side of the viewport each endpoint lies on.

highlighted = computed this step

Step 1 — Set up

Set up the exact input values.

rect and segment({’xmin’: Fraction(1, 1), ’xmax’: Fraction(5, 1), ’ymin’: Fraction(1, 1), ’ymax’: Fraction(4, 1)}, (0, 5), (6, 2))\begin{array}{c|c}\text{rect and segment}&\text{(\{'xmin': Fraction(1, 1), 'xmax': Fraction(5, 1), 'ymin': Fraction(1, 1), 'ymax': Fraction(4, 1)\}, (0, 5), (6, 2))}\end{array}
Line clippingA segment is clipped against the rectangular viewport.AB

Step 2 — Endpoint A

Compute the highlighted value.

A outcode1001\begin{array}{c|c}\text{A outcode}&\hlmath{\text{1001}}\end{array}
Line clippingA segment is clipped against the rectangular viewport.AB

Step 3 — Endpoint B

Compute the highlighted value.

B outcode0010\begin{array}{c|c}\text{B outcode}&\hlmath{\text{0010}}\end{array}
Line clippingA segment is clipped against the rectangular viewport.AB

Step 4 — Result

State the structural verdict.

OR, AND, verdict(1011, 0000, clip)\begin{array}{c|c}\text{OR, AND, verdict}&\hlmath{\text{(1011, 0000, clip)}}\end{array}
Line clippingA segment is clipped against the rectangular viewport.AB
cohen-sutherland-outcodes An outcode records top, bottom, right, and left tests as bits, making trivial accept, trivial reject, and clipping cases structural.