IceRay.cpp

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/*
    O = Origin = impact point
    i = normalized vector along the x axis
    j = normalized vector along the y axis = actually the normal vector in O
    D = Direction vector, norm |D| = 1
    N = Projection of D on y axis, norm |N| = normal reaction
    T = Projection of D on x axis, norm |T| = tangential reaction
    R = Reflexion vector

              ^y
              |
              |
              |
       _  _  _| _ _ _
       *      *      *|
        \     |     /
         \    |N   /  |
         R\   |   /D
           \  |  /    |
            \ | /
    _________\|/______*_______>x
               O    T

    Let define theta = angle between D and N. Then cos(theta) = |N| / |D| = |N| since D is normalized.

    j|D = |j|*|D|*cos(theta) => |N| = j|D

    Then we simply have:

    D = N + T

    To compute tangential reaction :

    T = D - N

    To compute reflexion vector :

    R = N - T = N - (D-N) = 2*N - D
*/

// Precompiled Header
#include "Stdafx.h"


using namespace Opcode;

float Ray::SquareDistance(const Point& point, float* t) const
{
    Point Diff = point - mOrig;
    float fT = Diff | mDir;

    if(fT<=0.0f)
    {
        fT = 0.0f;
    }
    else
    {
        fT /= mDir.SquareMagnitude();
        Diff -= fT*mDir;
    }

    if(t) *t = fT;

    return Diff.SquareMagnitude();
}