anki-3d-engine/ThirdParty/Bullet/Extras/InverseDynamics/IDRandomUtil.cpp

#include <cmath>
#include <cstdlib>
#include <ctime>

#include "BulletInverseDynamics/IDConfig.hpp"
#include "BulletInverseDynamics/IDMath.hpp"
#include "IDRandomUtil.hpp"

namespace btInverseDynamics
{
// constants for random mass and inertia generation
// these are arbitrary positive values.
static const float mass_min = 0.001;
static const float mass_max = 1.0;

void randomInit() { srand(time(NULL)); }
void randomInit(unsigned seed) { srand(seed); }

int randomInt(int low, int high) { return rand() % (high + 1 - low) + low; }

float randomFloat(float low, float high)
{
	return low + static_cast<float>(rand()) / RAND_MAX * (high - low);
}

float randomMass() { return randomFloat(mass_min, mass_max); }

vec3 randomInertiaPrincipal()
{
	vec3 inertia;
	do
	{
		inertia(0) = randomFloat(mass_min, mass_max);
		inertia(1) = randomFloat(mass_min, mass_max);
		inertia(2) = randomFloat(mass_min, mass_max);
	} while (inertia(0) + inertia(1) < inertia(2) || inertia(0) + inertia(2) < inertia(1) ||
			 inertia(1) + inertia(2) < inertia(0));
	return inertia;
}

mat33 randomInertiaMatrix()
{
	// generate random valid inertia matrix by first getting valid components
	// along major axes and then rotating by random amount
	vec3 principal = randomInertiaPrincipal();
	mat33 rot(transformX(randomFloat(-BT_ID_PI, BT_ID_PI)) * transformY(randomFloat(-BT_ID_PI, BT_ID_PI)) *
			  transformZ(randomFloat(-BT_ID_PI, BT_ID_PI)));
	mat33 inertia;
	inertia(0, 0) = principal(0);
	inertia(0, 1) = 0;
	inertia(0, 2) = 0;
	inertia(1, 0) = 0;
	inertia(1, 1) = principal(1);
	inertia(1, 2) = 0;
	inertia(2, 0) = 0;
	inertia(2, 1) = 0;
	inertia(2, 2) = principal(2);
	return rot * inertia * rot.transpose();
}

vec3 randomAxis()
{
	vec3 axis;
	idScalar length;
	do
	{
		axis(0) = randomFloat(-1.0, 1.0);
		axis(1) = randomFloat(-1.0, 1.0);
		axis(2) = randomFloat(-1.0, 1.0);

		length = BT_ID_SQRT(BT_ID_POW(axis(0), 2) + BT_ID_POW(axis(1), 2) + BT_ID_POW(axis(2), 2));
	} while (length < 0.01);

	return axis / length;
}
}  // namespace btInverseDynamics