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Implicit surfaces: add normal vector

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Théophile Bastian 2018-02-13 13:22:41 +01:00
parent ebf3f7a267
commit 2789acb5c5
2 changed files with 16 additions and 0 deletions
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13
Implicit.cpp
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@ -3,3 +3,16 @@
double ImplicitSurface::operator()(const Point& pt) const { double ImplicitSurface::operator()(const Point& pt) const {
return operator()(pt.x, pt.y, pt.z); return operator()(pt.x, pt.y, pt.z);
} }
Point ImplicitSurface::normal_at(const Point& pt) const {
// this is simply the gradient.
static const double d_dist = 1e-8;
return Point(
(operator()(pt.x + d_dist, pt.y, pt.z) -
operator()(pt.x - d_dist, pt.y, pt.z)) / (2. * d_dist),
(operator()(pt.x, pt.y + d_dist, pt.z) -
operator()(pt.x, pt.y - d_dist, pt.z)) / (2. * d_dist),
(operator()(pt.x, pt.y, pt.z + d_dist) -
operator()(pt.x, pt.y, pt.z - d_dist)) / (2. * d_dist));
}

3
Implicit.hpp
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@ -7,6 +7,9 @@ class ImplicitSurface {
virtual double operator() (double x, double y, double z) const = 0; virtual double operator() (double x, double y, double z) const = 0;
double operator()(const Point& pt) const; double operator()(const Point& pt) const;
Point getCenter() const { return center;} Point getCenter() const { return center;}
/// Compute the normal vector to the isosurface at `pt`
Point normal_at(const Point& pt) const;
protected: protected:
Point center; Point center;
ImplicitSurface(Point _center) : center(_center) {} ImplicitSurface(Point _center) : center(_center) {}