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Replace calcAngle() with inCircle() to avoid expensive trigonometry

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This commit is contained in:
Nigel Barber 2018-04-16 20:47:12 +01:00
parent b256f4940b
commit fe8e02c997
1 changed files with 25 additions and 21 deletions
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46
Source/geom.c
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@ -260,30 +260,34 @@ void tesedgeIntersect( TESSvertex *o1, TESSvertex *d1,
v->t = Interpolate( z1, o2->t, z2, d2->t );
}
}
/*
Calculate the angle between v1-v2 and v1-v0
*/
TESSreal calcAngle( TESSvertex *v0, TESSvertex *v1, TESSvertex *v2 )
{
TESSreal num, den, ax, ay, bx, by;
ax = v2->s - v1->s;
ay = v2->t - v1->t;
bx = v0->s - v1->s;
by = v0->t - v1->t;
num = ax * bx + ay * by;
den = sqrt( ax * ax + ay * ay ) * sqrt( bx * bx + by * by );
if ( den > 0.0 ) num /= den;
if ( num < -1.0 ) num = -1.0;
if ( num > 1.0 ) num = 1.0;
return acos( num );
}
TESSreal inCircle( TESSvertex *v, TESSvertex *v0, TESSvertex *v1, TESSvertex *v2 ) {
TESSreal adx, ady, bdx, bdy, cdx, cdy;
TESSreal abdet, bcdet, cadet;
TESSreal alift, blift, clift;
adx = v0->s - v->s;
ady = v0->t - v->t;
bdx = v1->s - v->s;
bdy = v1->t - v->t;
cdx = v2->s - v->s;
cdy = v2->t - v->t;
abdet = adx * bdy - bdx * ady;
bcdet = bdx * cdy - cdx * bdy;
cadet = cdx * ady - adx * cdy;
alift = adx * adx + ady * ady;
blift = bdx * bdx + bdy * bdy;
clift = cdx * cdx + cdy * cdy;
return alift * bcdet + blift * cadet + clift * abdet;
}
/*
Returns 1 is edge is locally delaunay
*/
int tesedgeIsLocallyDelaunay( TESShalfEdge *e )
{
return (calcAngle(e->Lnext->Org, e->Lnext->Lnext->Org, e->Org) +
calcAngle(e->Sym->Lnext->Org, e->Sym->Lnext->Lnext->Org, e->Sym->Org)) < (M_PI + 0.01);
{
return inCircle(e->Sym->Lnext->Lnext->Org, e->Lnext->Org, e->Lnext->Lnext->Org, e->Org) < 0;
}