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Bugfix: overflow causing full object facets reversal when STL file has large coordinates. #1666

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This commit is contained in:
Alessandro Ranellucci 2014-01-02 18:50:54 +01:00
parent 6afc01c3b9
commit 713bdd8055
1 changed files with 10 additions and 7 deletions
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17
xs/src/admesh/util.c
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@ -376,19 +376,22 @@ void stl_calculate_volume(stl_file *stl)
static float get_area(stl_facet *facet)
{
float cross[3][3];
double cross[3][3];
float sum[3];
float n[3];
float area;
int i;
// cast to double before calculating cross product because large coordinates
// can result in overflowing product
// (bad area is responsible for bad volume and bad facets reversal)
for(i = 0; i < 3; i++){
cross[i][0]=((facet->vertex[i].y * facet->vertex[(i + 1) % 3].z) -
(facet->vertex[i].z * facet->vertex[(i + 1) % 3].y));
cross[i][1]=((facet->vertex[i].z * facet->vertex[(i + 1) % 3].x) -
(facet->vertex[i].x * facet->vertex[(i + 1) % 3].z));
cross[i][2]=((facet->vertex[i].x * facet->vertex[(i + 1) % 3].y) -
(facet->vertex[i].y * facet->vertex[(i + 1) % 3].x));
cross[i][0]=(((double)facet->vertex[i].y * (double)facet->vertex[(i + 1) % 3].z) -
((double)facet->vertex[i].z * (double)facet->vertex[(i + 1) % 3].y));
cross[i][1]=(((double)facet->vertex[i].z * (double)facet->vertex[(i + 1) % 3].x) -
((double)facet->vertex[i].x * (double)facet->vertex[(i + 1) % 3].z));
cross[i][2]=(((double)facet->vertex[i].x * (double)facet->vertex[(i + 1) % 3].y) -
((double)facet->vertex[i].y * (double)facet->vertex[(i + 1) % 3].x));
}
sum[0] = cross[0][0] + cross[1][0] + cross[2][0];