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Make lwgeom_subdivide use lwgeom_intersection for clipping #281

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Make lwgeom_subdivide use lwgeom_intersection for clipping #281

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33 changes: 23 additions & 10 deletions liblwgeom/lwgeom.c
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Expand Up @@ -2249,10 +2249,10 @@ lwgeom_grid(const LWGEOM *lwgeom, const gridspec *grid)


/* Prototype for recursion */
static int lwgeom_subdivide_recursive(const LWGEOM *geom, uint32_t maxvertices, uint32_t depth, LWCOLLECTION *col);
static int lwgeom_subdivide_recursive(const LWGEOM *geom, uint8_t dimension, uint32_t maxvertices, uint32_t depth, LWCOLLECTION *col);

static int
lwgeom_subdivide_recursive(const LWGEOM *geom, uint32_t maxvertices, uint32_t depth, LWCOLLECTION *col)
lwgeom_subdivide_recursive(const LWGEOM *geom, uint8_t dimension, uint32_t maxvertices, uint32_t depth, LWCOLLECTION *col)
{
const uint32_t maxdepth = 50;
GBOX clip, subbox1, subbox2;
Expand All @@ -2275,7 +2275,7 @@ lwgeom_subdivide_recursive(const LWGEOM *geom, uint32_t maxvertices, uint32_t de

if ( width == 0.0 && height == 0.0 )
{
if ( geom->type == POINTTYPE )
if ( geom->type == POINTTYPE && dimension == 0)
{
lwcollection_add_lwgeom(col, lwgeom_clone_deep(geom));
return 1;
Expand Down Expand Up @@ -2303,12 +2303,19 @@ lwgeom_subdivide_recursive(const LWGEOM *geom, uint32_t maxvertices, uint32_t de
LWCOLLECTION *incol = (LWCOLLECTION*)geom;
int n = 0;
/* Don't increment depth yet, since we aren't actually
* subdividing geomtries yet */
* subdividing geometries yet */
for ( i = 0; i < incol->ngeoms; i++ )
n += lwgeom_subdivide_recursive(incol->geoms[i], maxvertices, depth, col);
n += lwgeom_subdivide_recursive(incol->geoms[i], dimension, maxvertices, depth, col);
return n;
}

if (lwgeom_dimension(geom) < dimension)
{
/* We've hit a lower dimension object produced by clipping at
* a shallower recursion level. Ignore it. */
return 0;
}

/* But don't go too far. 2^50 ~= 10^15, that's enough subdivision */
/* Just add what's left */
if ( depth > maxdepth )
Expand Down Expand Up @@ -2391,17 +2398,23 @@ lwgeom_subdivide_recursive(const LWGEOM *geom, uint32_t maxvertices, uint32_t de

++depth;

clipped = lwgeom_clip_by_rect(geom, subbox1.xmin, subbox1.ymin, subbox1.xmax, subbox1.ymax);
LWGEOM* subbox = (LWGEOM*) lwpoly_construct_envelope(geom->srid, subbox1.xmin, subbox1.ymin, subbox1.xmax, subbox1.ymax);
clipped = lwgeom_intersection(geom, subbox);
lwgeom_simplify_in_place(clipped, 0.0, LW_TRUE);
lwgeom_free(subbox);
if (clipped)
{
n += lwgeom_subdivide_recursive(clipped, maxvertices, depth, col);
n += lwgeom_subdivide_recursive(clipped, dimension, maxvertices, depth, col);
lwgeom_free(clipped);
}

clipped = lwgeom_clip_by_rect(geom, subbox2.xmin, subbox2.ymin, subbox2.xmax, subbox2.ymax);
subbox = (LWGEOM*) lwpoly_construct_envelope(geom->srid, subbox2.xmin, subbox2.ymin, subbox2.xmax, subbox2.ymax);
clipped = lwgeom_intersection(geom, subbox);
lwgeom_simplify_in_place(clipped, 0.0, LW_TRUE);
lwgeom_free(subbox);
if (clipped)
{
n += lwgeom_subdivide_recursive(clipped, maxvertices, depth, col);
n += lwgeom_subdivide_recursive(clipped, dimension, maxvertices, depth, col);
lwgeom_free(clipped);
}

Expand All @@ -2426,7 +2439,7 @@ lwgeom_subdivide(const LWGEOM *geom, uint32_t maxvertices)
lwerror("%s: cannot subdivide to fewer than %d vertices per output", __func__, minmaxvertices);
}

lwgeom_subdivide_recursive(geom, maxvertices, startdepth, col);
lwgeom_subdivide_recursive(geom, lwgeom_dimension(geom), maxvertices, startdepth, col);
lwgeom_set_srid((LWGEOM*)col, geom->srid);
return col;
}
Expand Down