From 1614e9ee900ee3ac2a0282354195709ef9815b62 Mon Sep 17 00:00:00 2001
From: Paul McCarthy <pauldmccarthy@gmail.com>
Date: Sat, 15 Jul 2017 22:24:23 +0100
Subject: [PATCH] Mesh class calculates normals. Implementations are crap
---
fsl/data/mesh.py | 70 ++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 68 insertions(+), 2 deletions(-)
diff --git a/fsl/data/mesh.py b/fsl/data/mesh.py
index 2a9c47df7..82023debd 100644
--- a/fsl/data/mesh.py
+++ b/fsl/data/mesh.py
@@ -53,6 +53,12 @@ class TriangleMesh(object):
``indices`` A :meth:`M\times 3` ``numpy`` array containing
the vertex indices for :math:`M` triangles
+
+ ``normals`` A :math:`M\times 3` ``numpy`` array containing
+ face normals.
+
+ ``vnormals`` A :math:`N\times 3` ``numpy`` array containing
+ vertex normals.
============== ====================================================
@@ -101,8 +107,10 @@ class TriangleMesh(object):
self.indices = np.array(indices).reshape((-1, 3))
self.__vertexData = {}
- self.__loBounds = self.vertices.min(axis=0)
- self.__hiBounds = self.vertices.max(axis=0)
+ self.__faceNormals = None
+ self.__vertNormals = None
+ self.__loBounds = self.vertices.min(axis=0)
+ self.__hiBounds = self.vertices.max(axis=0)
def __repr__(self):
@@ -118,6 +126,64 @@ class TriangleMesh(object):
return self.__repr__()
+ @property
+ def normals(self):
+ """Returns a ``(M, 3)`` array containing normals for every triangle
+ in the mesh.
+ """
+ if self.__faceNormals is not None:
+ return self.__faceNormals
+
+ v1 = self.vertices[self.indices[:, 0]]
+ v2 = self.vertices[self.indices[:, 1]]
+
+ fnormals = np.cross(v1, v2)
+
+ # TODO make fast, and make sure that this actually works.
+ for i in range(self.indices.shape[0]):
+
+ p0, p1, p2 = self.vertices[self.indices[i], :]
+ n = fnormals[i, :]
+
+ if np.dot(n, np.cross(p1 - p0, p2 - p0)) > 0:
+ fnormals[i, :] *= -1
+
+ self.__faceNormals = fnormals
+
+ return self.__faceNormals
+
+
+ @property
+ def vnormals(self):
+ """Returns a ``(N, 3)`` array containing normals for every vertex
+ in the mesh.
+ """
+ if self.__vertNormals is not None:
+ return self.__vertNormals
+
+ # per-face normals
+ fnormals = self.normals
+
+ vnormals = np.zeros((self.vertices.shape[0], 3), dtype=np.float)
+
+ # TODO make fast
+ for i in range(self.indices.shape[0]):
+
+ v0, v1, v2 = self.indices[i]
+
+ vnormals[v0, :] += fnormals[i]
+ vnormals[v1, :] += fnormals[i]
+ vnormals[v2, :] += fnormals[i]
+
+ # normalise to unit length
+ lens = np.sqrt(np.sum(vnormals * vnormals, axis=1))
+ vnormals = (vnormals.T / lens).T
+
+ self.__vertNormals = vnormals
+
+ return self.__vertNormals
+
+
def getBounds(self):
"""Returns a tuple of values which define a minimal bounding box that
will contain all vertices in this ``TriangleMesh`` instance. The
--
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