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new function barycentric_weights_v2_quad(), like barycentric_weights_v2 but for quads.

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takes vecs and a point and assigns 4 weights, needed for nice quad interpolation for mask feathering.
This commit is contained in:
Campbell Barton
2012-07-13 09:19:05 +00:00
parent 6ee2e0b145
commit 73c2abe83d
2 changed files with 42 additions and 0 deletions
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2
source/blender/blenlib/BLI_math_geom.h
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@@ -200,6 +200,8 @@ void barycentric_transform(float pt_tar[3], float const pt_src[3],
void barycentric_weights_v2(const float v1[2], const float v2[2], const float v3[2],
const float co[2], float w[3]);
void barycentric_weights_v2_quad(const float v1[2], const float v2[2], const float v3[2], const float v4[2],
const float co[2], float w[4]);
int barycentric_coords_v2(const float v1[2], const float v2[2], const float v3[2], const float co[2], float w[3]);
int barycentric_inside_triangle_v2(const float w[3]);

40
source/blender/blenlib/intern/math_geom.c
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@@ -1942,6 +1942,46 @@ void barycentric_weights_v2(const float v1[2], const float v2[2], const float v3
}
}
/* same as #barycentric_weights_v2 but works with a quad,
* note: untested for values outside the quad's bounds.
* note: there may be a more efficient method to do this, just figured it out - campbell */
void barycentric_weights_v2_quad(const float v1[2], const float v2[2], const float v3[2], const float v4[2],
const float co[2], float w[4])
{
float wtot;
const float areas_co[4] = {
area_tri_signed_v2(v1, v2, co),
area_tri_signed_v2(v2, v3, co),
area_tri_signed_v2(v3, v4, co),
area_tri_signed_v2(v4, v1, co),
};
const float areas_diag[4] = {
area_tri_signed_v2(v4, v1, v2),
area_tri_signed_v2(v1, v2, v3),
area_tri_signed_v2(v2, v3, v4),
area_tri_signed_v2(v3, v4, v1),
};
const float u = areas_co[3] / (areas_co[1] + areas_co[3]);
const float v = areas_co[0] / (areas_co[0] + areas_co[2]);
w[0] = ((1.0f - u) * (1.0f - v)) * sqrtf(areas_diag[0] / areas_diag[2]);
w[1] = (( u) * (1.0f - v)) * sqrtf(areas_diag[1] / areas_diag[3]);
w[2] = (( u) * ( v)) * sqrtf(areas_diag[2] / areas_diag[0]);
w[3] = ((1.0f - u) * ( v)) * sqrtf(areas_diag[3] / areas_diag[1]);
wtot = w[0] + w[1] + w[2] + w[3];
if (wtot != 0.0f) {
mul_v4_fl(w, 1.0f / wtot);
}
else { /* dummy values for zero area face */
copy_v4_fl(w, 1.0f / 4.0f);
}
}
/* given 2 triangles in 3D space, and a point in relation to the first triangle.
* calculate the location of a point in relation to the second triangle.
* Useful for finding relative positions with geometry */