Cohen-Sutherland Outcodes - Computer Graphics Step by Step

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

cohen-sutherland-outcodes An outcode records top, bottom, right, and left tests as bits, making trivial accept, trivial reject, and clipping cases structural.

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.

\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}

Step 2 — Endpoint A

Compute the highlighted value.

\begin{array}{c|c}\text{A outcode}&\hlmath{\text{1001}}\end{array}

Step 3 — Endpoint B

Compute the highlighted value.

\begin{array}{c|c}\text{B outcode}&\hlmath{\text{0010}}\end{array}

Step 4 — Result

State the structural verdict.

\begin{array}{c|c}\text{OR, AND, verdict}&\hlmath{\text{(1011, 0000, clip)}}\end{array}