jc_voronoi_clip.h

jc_voronoi_clip.h provides jcv_clipper callbacks that clip Voronoi cells to a caller-supplied convex polygon.

Types

Functions

Include the implementation

Define both implementation macros in exactly one translation unit:

#define JC_VORONOI_IMPLEMENTATION
#include "jc_voronoi.h"

#define JC_VORONOI_CLIP_IMPLEMENTATION
#include "jc_voronoi_clip.h"

Other translation units can include jc_voronoi_clip.h without either define. The clipping header includes jc_voronoi.h itself.

jcv_clipping_polygon

typedef struct jcv_clipping_polygon_ {
    jcv_point* points;
    int num_points;
} jcv_clipping_polygon;

points describes a convex polygon with counter-clockwise winding. Supply at least three vertices in boundary order. The polygon and its point array remain owned by the caller and must stay valid throughout diagram generation.

Polygon clipper callbacks

These functions implement the three callback roles declared by jc_voronoi.h. Applications normally assign them to a jcv_clipper; they do not call them directly.

jcv_clip_polygon_test_point

int jcv_clip_polygon_test_point(
    const jcv_clipper* clipper,
    jcv_point point);

Returns non-zero when point is inside the convex polygon referenced by clipper->ctx.

jcv_clip_polygon_clip_edge

int jcv_clip_polygon_clip_edge(
    const jcv_clipper* clipper,
    jcv_edge* edge);

Clips edge to the convex polygon and returns non-zero when a segment remains.

jcv_clip_polygon_fill_gaps

void jcv_clip_polygon_fill_gaps(
    const jcv_clipper* clipper,
    jcv_context_internal* allocator,
    jcv_site* site);

Adds polygon-boundary edges needed to close the site’s cell.

Complete setup

jcv_point boundary[] = {
    { 50, 10 },
    { 90, 90 },
    { 10, 90 }
};

jcv_clipping_polygon polygon = {
    boundary,
    (int)(sizeof(boundary) / sizeof(boundary[0]))
};

jcv_clipper clipper = {0};
clipper.test_fn = jcv_clip_polygon_test_point;
clipper.clip_fn = jcv_clip_polygon_clip_edge;
clipper.fill_fn = jcv_clip_polygon_fill_gaps;
clipper.ctx = &polygon;

jcv_diagram diagram = {0};
jcv_diagram_generate(num_points, points, NULL, &clipper, &diagram);

/* Read clipped cells and edges here. */

jcv_diagram_free(&diagram);

The generator derives the clipper’s preliminary min and max bounds, so callers do not need to initialize those members. Passing an explicit jcv_rect still prunes input points outside that rectangle before producing the polygon-clipped result.

See the custom clipping example for the same setup in context.