source: GTP/trunk/App/Demos/Vis/FriendlyCulling/src/Halton.cpp @ 3322

#include "common.h"
#include "Halton.h"



void Halton::TestHalton(int n, int dim)
{
        Halton h(dim);

        for (int i = 1; i <= n; ++ i)
        {
                std::cout << "halton " << i << " of dim " << dim << " = " << h.GetNext() << std::endl;
        }
}


void Halton::TestPrime()
{
        int dim = 2;

        for (int i = 1; i < 10; ++ i)
        {
                std::cout << "prime for dim " << i << " " << Halton::FindPrime(i) << std::endl;
        }
}


Halton::Halton(int dim): mIndex(0)
{
        mBase = FindPrime(dim);
}


float Halton::GetNext()
{
        ++ mIndex;

        float result = .0f;
        float fraction = 1.0f / (float)mBase;
        int idx = mIndex;

        while (idx > 0) 
        {
                int digit = idx % mBase;
                result += fraction * (float)digit;

                idx  = (idx - digit) / mBase;
                fraction /= (float)mBase;
        }

        //mIndex %= 100000000;
        return result;
}


bool Halton::IsPrime(int n) 
{
        bool isPrime = true;

        for (int i = 2; i < n; ++ i) 
        {
                if (n % i == 0) 
                {
                        isPrime = false;
                        break;
                }
        }

        return isPrime;
}
 

int Halton::FindPrime(int idx) 
{
        if (idx < 1) 
        {
                std::cerr << "error: cannot find " << idx << "th prime" << std::endl;
                return 0;
        }

        // only even prime number
        if (idx == 1) return 2;

        int number = 3;
        int primeFound = 1;

        while (1)
        {
                if (IsPrime(number)) ++ primeFound;
                if (primeFound == idx) break;

                number += 2;
        }

        return number;
}


void HaltonSequence::TestHalton(int n, int dim)
{
        HaltonSequence h(dim);
        float *haltons = new float[dim];

        for (int i = 1; i <= n; ++ i)
        {
                h.GetNext(haltons);
                std::cout << "halton " << i << " of dim " << dim << " = ";

                for (int j = 0; j < dim; ++ j)
                        std::cout << haltons[j] << " ";

                std::cout << std::endl;
        }
}


HaltonSequence::HaltonSequence(int dim)
{
        for (int i = 0; i < dim; ++ i)
        {
                mHaltons.push_back(Halton(i + 1));
        }
}


void HaltonSequence::GetNext(float *numbers)
{
        for (size_t i = 0; i < mHaltons.size(); ++ i)
        {
                numbers[i] = mHaltons[i].GetNext();
        }
}