Bugfix: overflow causing full object facets reversal when STL file has large coordinates. #1666
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@ -376,19 +376,22 @@ void stl_calculate_volume(stl_file *stl)
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static float get_area(stl_facet *facet)
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static float get_area(stl_facet *facet)
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{
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{
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float cross[3][3];
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double cross[3][3];
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float sum[3];
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float sum[3];
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float n[3];
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float n[3];
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float area;
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float area;
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int i;
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int i;
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// cast to double before calculating cross product because large coordinates
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// can result in overflowing product
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// (bad area is responsible for bad volume and bad facets reversal)
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for(i = 0; i < 3; i++){
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for(i = 0; i < 3; i++){
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cross[i][0]=((facet->vertex[i].y * facet->vertex[(i + 1) % 3].z) -
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cross[i][0]=(((double)facet->vertex[i].y * (double)facet->vertex[(i + 1) % 3].z) -
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(facet->vertex[i].z * facet->vertex[(i + 1) % 3].y));
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((double)facet->vertex[i].z * (double)facet->vertex[(i + 1) % 3].y));
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cross[i][1]=((facet->vertex[i].z * facet->vertex[(i + 1) % 3].x) -
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cross[i][1]=(((double)facet->vertex[i].z * (double)facet->vertex[(i + 1) % 3].x) -
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(facet->vertex[i].x * facet->vertex[(i + 1) % 3].z));
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((double)facet->vertex[i].x * (double)facet->vertex[(i + 1) % 3].z));
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cross[i][2]=((facet->vertex[i].x * facet->vertex[(i + 1) % 3].y) -
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cross[i][2]=(((double)facet->vertex[i].x * (double)facet->vertex[(i + 1) % 3].y) -
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(facet->vertex[i].y * facet->vertex[(i + 1) % 3].x));
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((double)facet->vertex[i].y * (double)facet->vertex[(i + 1) % 3].x));
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}
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}
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sum[0] = cross[0][0] + cross[1][0] + cross[2][0];
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sum[0] = cross[0][0] + cross[1][0] + cross[2][0];
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