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Fix computation of normals for Surface

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This commit is contained in:
Grant Sanderson 2024-02-13 14:48:00 -06:00
parent d44e248277
commit 4ce8a3ba9d
1 changed files with 18 additions and 10 deletions
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28
manimlib/mobject/types/surface.py
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@ -133,20 +133,28 @@ class Surface(Mobject):
if len(indices) == 0:
return np.zeros((3, 0))
left = indices - 1
right = indices + 1
up = indices - nv
down = indices + nv
# For each point, find two adjacent points at indices
# step1 and step2, such that crossing points[step1] - points
# with points[step1] - points gives a normal vector
step1 = indices + 1
step2 = indices + nu
left[0] = indices[0]
right[-1] = indices[-1]
up[:nv] = indices[:nv]
down[-nv:] = indices[-nv:]
# Right edge
step1[nu - 1::nu] = indices[nu - 1::nu] + nu
step2[nu - 1::nu] = indices[nu - 1::nu] - 1
# Bottom edge
step1[-nu:] = indices[-nu:] - nu
step2[-nu:] = indices[-nu:] + 1
# Lower right point
step1[-1] = indices[-1] - 1
step2[-1] = indices[-1] - nu
points = self.get_points()
crosses = cross(
points[right] - points[left],
points[up] - points[down],
points[step1] - points,
points[step2] - points,
)
self.data["normal"] = normalize_along_axis(crosses, 1)
return self.data["normal"]