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fix: symmetric ambiguous dual-plane cases require special treatment

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JDWarner
2013-08-30 12:36:31 -05:00
committed by Josh Warner (Mac)
parent 44c04996c7
commit 296d102047
1 changed files with 28 additions and 1 deletions
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skimage/measure/_marching_cubes_cy.pyx
+28 -1
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@@ -184,7 +184,10 @@ def iterate_and_store_3d(cnp.ndarray[double, ndim=3] arr,
# Cases 0 and 255 are entirely below/above the contour.
if cube_case > 127:
cube_case = 255 - cube_case
if ((cube_case != 150) and
(cube_case != 170) and
(cube_case != 195)):
cube_case = 255 - cube_case
# Calculate cube edges, to become triangulation vertices.
# If we moved in a convenient direction, save 1/3 of the effort by
@@ -963,5 +966,29 @@ def _append_tris(list tri_list, unsigned char case, tuple e1, tuple e2,
elif (case == 127):
# Isolated corner v8
tri_list.append([e11, e7, e8])
elif (case == 150):
# AMBIGUOUS CASE: back right and front left planes
# In these cube_case > 127 cases, the vertices are identical BUT
# they are connected in the opposite fashion.
_append_tris(tri_list, 6, e1, e2, e3, e4, e5, e6, e7, e8, e9, e10,
e11, e12)
_append_tris(tri_list, 111, e1, e2, e3, e4, e5, e6, e7, e8, e9, e10,
e11, e12)
elif (case == 170):
# AMBIGUOUS CASE: upper left and lower right planes
# In these cube_case > 127 cases, the vertices are identical BUT
# they are connected in the opposite fashion.
_append_tris(tri_list, 119, e1, e2, e3, e4, e5, e6, e7, e8, e9, e10,
e11, e12)
_append_tris(tri_list, 34, e1, e2, e3, e4, e5, e6, e7, e8, e9, e10,
e11, e12)
elif (case == 195):
# AMBIGUOUS CASE: back upper and front lower planes
# In these cube_case > 127 cases, the vertices are identical BUT
# they are connected in the opposite fashion.
_append_tris(tri_list, 63, e1, e2, e3, e4, e5, e6, e7, e8, e9, e10,
e11, e12)
_append_tris(tri_list, 3, e1, e2, e3, e4, e5, e6, e7, e8, e9, e10,
e11, e12)
return