RayTrace.h

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#include <iostream>
#include <vector>
#include <array>
#include <cmath>
#include <thread>
 
#include "Utils.h"
#include "Structs.h"
#include "RTRefls.h"
 
#define _USE_MATH_DEFINES
 
#ifndef __RayTracer_h
#define __RayTracer_h
 
/*! \file RayTrace.h
    \brief Functions for RT calculations on CPU.
 
    Provides functions for performing PO calculations on the CPU.
*/
 
/**
 * Ray-trace class.
 *
 * Contains methods for performing ray-traces between arbitrarily oriented and curved surfaces.
 *
 * @see Utils
 * @see RTRefls
 */
template<class T, class U, class V>
class RayTracer
{
    int numThreads;
    int step;
    int nTot;
 
    V epsilon;
 
    void joinThreads();
 
public:
    Utils<V> ut;    /**<Utils object.*/
    std::vector<std::thread> threadPool;    /**<Vector of thread object.*/
 
    RayTracer(int numThreads, int nTot, V epsilon, bool verbose = false);
 
    void transfRays(T ctp, U *fr, bool inv = false);
 
    void propagateRaysToTarget(int start, int stop,
                      T ctp, U *fr_in, U *fr_out, V t0);
 
    void parallelRays(T ctp, U *fr_in, U *fr_out, V t0);
};
 
/**
 * Constructor.
 *
 * Set internal parameters for ray-tracing.
 *
 * @param numThreads Number of computing threads to employ.
 * @param nTot Total amount of rays in beam.
 * @param epsilon Precision of NR method, double/float.
 * @param verbose Whether or not to print internal state information upon construction.
 */
template<class T, class U, class V>
RayTracer<T, U, V>::RayTracer(int numThreads, int nTot, V epsilon, bool verbose)
{
    this->numThreads = numThreads;
    this->step = ceil(nTot / numThreads);
    this->nTot = nTot;
    this->threadPool.resize(numThreads);
    this->epsilon = epsilon;
}
 
/**
 * Transform to surface.
 *
 * Transform ray-trace frame into target surface restframe, using target surface transformation matrix.
 *
 * @param ctp reflparams or reflparamsf of target surface.
 * @param fr Pointer to cframe or cframef object to be transformed.
 * @param inv Whether or not to apply the inverse of the transformation matrix.
 *
 * @see reflparams
 * @see reflparamsf
 * @see cframe
 * @see cframef
 */
template<class T, class U, class V>
void RayTracer<T, U, V>::transfRays(T ctp, U *fr, bool inv)
{
    bool vec = true;
    std::array<V, 3> inp, out;
    for (int i=0; i<fr->size; i++)
    {
        inp[0] = fr->x[i];
        inp[1] = fr->y[i];
        inp[2] = fr->z[i];
 
        if (inv) {ut.invmatVec4(ctp.transf, inp, out);}
        else {ut.matVec4(ctp.transf, inp, out);}
 
        fr->x[i] = out[0];
        fr->y[i] = out[1];
        fr->z[i] = out[2];
 
        inp[0] = fr->dx[i];
        inp[1] = fr->dy[i];
        inp[2] = fr->dz[i];
 
        if (inv) {ut.invmatVec4(ctp.transf, inp, out, vec);}
        else {ut.matVec4(ctp.transf, inp, out, vec);}
 
        fr->dx[i] = out[0];
        fr->dy[i] = out[1];
        fr->dz[i] = out[2];
    }
}
 
/**
 * Propagate rays to target.
 *
 * Propagate a frame of rays to a target surface.
 *
 * @param start Index of first loop iteration in parallel block.
 * @param stop Index of last loop iteration in parallel block.
 * @param ctp reflparams or reflparamsf object containing target surface parameters.
 * @param fr_in Pointer to input cframe or cframef object.
 * @param fr_out Pointer to output cframe or cframef object.
 * @param t0 Starting guess for NR method, double/float.
 *
 * @see reflparams
 * @see reflparamsf
 * @see cframe
 * @see cframef
 */
template<class T, class U, class V>
void RayTracer<T, U, V>::propagateRaysToTarget(int start, int stop,
                  T ctp, U *fr_in, U *fr_out, V t0)
{
    int flip = 1;
 
    if (ctp.flip)
    {
        flip = -1;
    }
 
    V (*refl_func_ptr)(V, V, V, V, V, V, V, V, V, V);
    std::array<V, 3> (*refl_norm_ptr)(V, V, V, int, V, V, V);
 
    if (ctp.type == 0)
    {
        refl_func_ptr = &RTRefls<V>::gp;
        refl_norm_ptr = &RTRefls<V>::np;
    }
 
    if (ctp.type == 1) 
    {
        refl_func_ptr = &RTRefls<V>::gh;
        refl_norm_ptr = &RTRefls<V>::nh;
    }
    
    else if (ctp.type == 2) 
    {
        refl_func_ptr = &RTRefls<V>::ge;
        refl_norm_ptr = &RTRefls<V>::ne;
    }
    
    else if (ctp.type == 3) 
    {
        refl_func_ptr = &RTRefls<V>::gpl;
        refl_norm_ptr = &RTRefls<V>::npl;
    }
    
    std::array<V, 3> direct; // Store incoming ray
    std::array<V, 3> out; // Store reflected/refracted ray
    
    for (int i=start; i<stop; i++)
    {
        V _t = t0;
        V t1 = 1e99;
 
        V check = fabs(t1 - _t);
        std::array<V, 3> norms;
 
        V x = fr_in->x[i];
        V y = fr_in->y[i];
        V z = fr_in->z[i];
 
        V dx = fr_in->dx[i];
        V dy = fr_in->dy[i];
        V dz = fr_in->dz[i];
        
        direct = {dx, dy, dz};
        
        while (check > epsilon)
        {
            t1 = refl_func_ptr(_t, x, y, z, dx, dy, dz, ctp.coeffs[0], ctp.coeffs[1], ctp.coeffs[2]);
 
            check = fabs(t1 - _t);
 
            _t = t1;
        }
 
        if ((abs(round(dx)) == 0 && abs(round(dy)) == 0 && abs(round(dz)) == 0) || std::isnan(_t)) 
        {
            fr_out->x[i] = x;
            fr_out->y[i] = y;
            fr_out->z[i] = z;
        
            fr_out->dx[i] = 0; // Set at 2: since beta should be normalized, can select on 2
            fr_out->dy[i] = 0;
            fr_out->dz[i] = 0;
        }
 
        else
        {
            fr_out->x[i] = x + _t*dx;
            fr_out->y[i] = y + _t*dy;
            fr_out->z[i] = z + _t*dz;
 
            norms = refl_norm_ptr(fr_out->x[i], fr_out->y[i], fr_out->z[i], flip, ctp.coeffs[0], ctp.coeffs[1], ctp.coeffs[2]);
            check = (dx*norms[0] + dy*norms[1] + dz*norms[2]);
 
            ut.snell(direct, norms, out);
 
            fr_out->dx[i] = out[0];
            fr_out->dy[i] = out[1];
            fr_out->dz[i] = out[2];
        }
    }
}
 
/**
 * Run ray-trace in parallel.
 *
 * Run a parallel ray-trace, depending on the type of target surface.
 *
 * @param ctp reflparams or reflparamsf object containing target surface parameters.
 * @param fr_in Pointer to input cframe or cframef object.
 * @param fr_out Pointer to output cframe or cframef object.
 * @param t0 Starting guess for NR method, double/float.
 *
 * @see reflparams
 * @see reflparamsf
 * @see cframe
 * @see cframef
 */
template <class T, class U, class V>
void RayTracer<T, U, V>::parallelRays(T ctp, U *fr_in, U *fr_out, V t0)
{
    int final_step;
 
    // Transform to reflector rest frame
    bool inv = true;
    transfRays(ctp, fr_in, inv);
 
    for(int n=0; n<numThreads; n++)
    {
        if(n == (numThreads-1)) {final_step = nTot;}
        else {final_step = (n+1) * step;}
            
        threadPool[n] = std::thread(&RayTracer::propagateRaysToTarget,
                                        this, n * step, final_step,
                                        ctp, fr_in, fr_out, t0);
    }
    joinThreads();
 
    // Transform back to real frame
    transfRays(ctp, fr_in);
    transfRays(ctp, fr_out);
}
 
template <class T, class U, class V>
void RayTracer<T, U, V>::joinThreads()
{
    for (std::thread &t : threadPool) {if (t.joinable()) {t.join();}}
}
#endif