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Added two functions to generate point inside a box and over the surface of a sphere.

This commit is contained in:
Paolo Cignoni 2013-02-23 06:15:23 +00:00
parent 26392a560b
commit d3d50e6858
1 changed files with 43 additions and 6 deletions

49
vcg/math/random_generator.h
View File

@ -63,8 +63,44 @@ public:
/// Generates a random number in the (0,1) real interval. /// Generates a random number in the (0,1) real interval.
virtual double generate01open()=0; virtual double generate01open()=0;
virtual double generateRange(double minV, double maxV) { return minV+(maxV-minV)*generate01(); } virtual double generateRange(double minV, double maxV) { return minV+(maxV-minV)*generate01(); }
}; };
template <class ScalarType, class GeneratorType>
void GeneratePointInBox3Uniform(GeneratorType &rnd, const Box3<ScalarType> &bb, Point3<ScalarType> &p)
{
p = Point3<ScalarType>(
(ScalarType) rnd.generateRange(double(bb.min[0]),double(bb.max[0])),
(ScalarType) rnd.generateRange(double(bb.min[1]),double(bb.max[1])),
(ScalarType) rnd.generateRange(double(bb.min[2]),double(bb.max[2]))
);
}
/*
* This is the algorithm proposed by George Marsaglia [1]
* to generate a point over a unit sphere
* Independently generate V1 and V2, taken from a uniform distribution on (-1,1) such that
* S=(V1^2+V2^2)<1
*
* The random vector is then :
* (2V1 sqrt(1-S), 2V2 sqrt(1-S),1-2S)
*
* Marsaglia, G. "Choosing a Point from the Surface of a Sphere." Ann. Math. Stat. 43, 645-646, 1972.
*/
template <class ScalarType, class GeneratorType>
void GeneratePointOnUnitSphereUniform(GeneratorType &rnd, Point3<ScalarType> &p)
{
double x,y,s;
do
{
x = 2.0*rnd.generate01()-1.0;
y = 2.0*rnd.generate01()-1.0;
s = x*x+y*y;
} while (s>1);
p[0]= ScalarType(2 * x * sqrt(1-s));
p[1]= ScalarType(2 * y * sqrt(1-s));
p[2]= ScalarType(1-2*s);
}
/** /**
* Uniform RNG derived from a STL extension of sgi. * Uniform RNG derived from a STL extension of sgi.
* *
@ -346,14 +382,15 @@ public:
}; };
/* boxmuller /* Returns a value with normal distribution with mean m, standard deviation s
* Implements the Polar form of the Box-Muller Transformation *
* (c) Copyright 1994, Everett F. Carter Jr. * It implements the Polar form of the Box-Muller Transformation
* Permission is granted by the author to use this software for any * A transformation which transforms from a two-dimensional continuous uniform distribution
* application provided this copyright notice is preserved. * to a two-dimensional bivariate normal distribution
* with mean m, standard deviation s
*/ */
inline double box_muller(RandomGenerator &generator, double m, double s) /* normal random variate generator */ inline double box_muller(RandomGenerator &generator, double m, double s) /* normal random variate generator */
{ /* mean m, standard deviation s */ { /* */
double x1, x2, w, y1; double x1, x2, w, y1;
static double y2; static double y2;
static int use_last = 0; static int use_last = 0;