Differential D2669 Diff 8797 source/blender/blenkernel/intern/mesh_evaluate.c

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source/blender/blenkernel/intern/mesh_evaluate.c

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	return total_area;	return total_area;
	}	}

		/* Calculate the volume and volume-weighted centroid of the volume formed by the polygon and the origin. */
		/* Results will be negative if the origin is "outside" the polygon (+ve normal side), but the polygon may be non-planar with no effect. */
		/* note: volume is 6x actual volume, and centroid is 4x actual volume-weighted centroid (so division can be done once at the end) */
		static float mesh_calc_poly_volume_and_weighted_centroid(
		const MPoly mpoly, const MLoop loopstart, const MVert *mvarray,
		float r_cent[3])
		{
		int i;
		float tetra_volume;
		float total_volume = 0.0f;
		float v1[3], v2[3], v3[3], tetra_cent[3];
		campbellbartonUnsubmitted Not Done Inline Actions No reason to copy into vectors, can assign coords to `const float ` as use them in-place. campbellbarton:* No reason to copy into vectors, can assign coords to `const float *` as use them in-place.
		float v1_cross_v2[3];

		copy_v3_v3(v1, mvarray[loopstart[0].v].co);
		copy_v3_v3(v2, mvarray[loopstart[1].v].co);
		zero_v3(r_cent);

		for (i = 2; i < mpoly->totloop; i++) {
		copy_v3_v3(v3, mvarray[loopstart[i].v].co);

		// Calculate the 6x volume of the tetrahedron formed by the 3 vertices of the triangle and the origin as the fourth vertex
		cross_v3_v3v3(v1_cross_v2, v1, v2);
		tetra_volume = dot_v3v3 (v1_cross_v2, v3);
		total_volume += tetra_volume;

		// Calculate the centroid of the tetrahedron formed by the 3 vertices of the triangle and the origin as the fourth vertex
		// The centroid is simply the average of the 4 vertices.
		// note that the vector is 4x the actual centroid so the division can be done once at the end
		add_v3_v3v3(tetra_cent, v1, v2);
		add_v3_v3(tetra_cent, v3);

		madd_v3_v3fl(r_cent, tetra_cent, tetra_volume);

		copy_v3_v3(v2, v3);
		}

		return total_volume;
		}

	#if 0 /* slow version of the function below */	#if 0 /* slow version of the function below */
	void BKE_mesh_calc_poly_angles(MPoly mpoly, MLoop loopstart,	void BKE_mesh_calc_poly_angles(MPoly mpoly, MLoop loopstart,
	MVert *mvarray, float angles[])	MVert *mvarray, float angles[])
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	return (me->totpoly != 0);	return (me->totpoly != 0);
	}	}

		bool BKE_mesh_center_solid_centroid(const Mesh *me, float r_cent[3])
		{
		int i = me->totpoly;
		MPoly *mpoly;
		float poly_volume;
		float total_volume = 0.0f;
		float poly_cent[3];

		zero_v3(r_cent);

		/* calculate a weighted average of polyhedron centroids */
		for (mpoly = me->mpoly; i--; mpoly++) {
		poly_volume = mesh_calc_poly_volume_and_weighted_centroid(mpoly, me->mloop + mpoly->loopstart, me->mvert, poly_cent);

		/* poly_cent is already volume-weighted, so no need to multiply by the volume */
		add_v3_v3(r_cent, poly_cent);
		total_volume += poly_volume;
		}
		/* otherwise we get NAN for 0 polys */
		if (me->totpoly) {
		campbellbartonUnsubmitted Not Done Inline Actions Should check `total_volume != 0.0f` instead. campbellbarton: Should check `total_volume != 0.0f` instead.
		/* multipy by 0.25 to get the correct centroid */
		/* no need to divide volume by 6 as the centroid is weighted by 6x the volume, so it all cancels out */
		mul_v3_fl(r_cent, 0.25f / total_volume);
		}

		/* zero area faces cause this, fallback to median */
		if (UNLIKELY(!is_finite_v3(r_cent))) {
		return BKE_mesh_center_median(me, r_cent);
		}

		return (me->totpoly != 0);
		}
	/** \} */	/** \} */


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