Question

In Illustrator, you can drag a rectangle and it will select all objects in it. It does beyond a bounding box test since it ensures its touching an actual part of the polygon. How does it efficiently do this then? (A C or C++ implementation would be preferable)

Thanks

Answer 1

If you want to check if any part of polygon P is within a rectangle R, then you can do this:

• If any vertex of P is within R, then return TRUE;
• If any vertex of R is within P, then return TRUE;
• If any edge of P (line between adjacent vertexes) intersects an edge of R, then return TRUE.
• Otherwise, return FALSE.