astronomy/demo/c/raytrace/reorient.cpp

/*
    reorient.cpp

    Copyright (C) 2013 by Don Cross  -  http://cosinekitty.com/raytrace

    This software is provided 'as-is', without any express or implied
    warranty. In no event will the author be held liable for any damages
    arising from the use of this software.

    Permission is granted to anyone to use this software for any purpose,
    including commercial applications, and to alter it and redistribute it
    freely, subject to the following restrictions:

    1. The origin of this software must not be misrepresented; you must not
       claim that you wrote the original software. If you use this software
       in a product, an acknowledgment in the product documentation would be
       appreciated but is not required.

    2. Altered source versions must be plainly marked as such, and must not be
       misrepresented as being the original software.

    3. This notice may not be removed or altered from any source
       distribution.

    -------------------------------------------------------------------------

    Implements class SolidObject_Reorientable, a base class for 
    solid objects that hides complexity of rotating and translating
    a solid object, so that the math needs only be solved for
    a fixed orientation and location.  This really helps for
    cases where the math gets complicated, like in class Torus.

    Coordinates of points and vectors are converted back and forth between
    "camera" space - <x,y,z> coordinates from the point of view of the 
    Scene object doing the rendering, and and "object" space - <r,s,t> coordinates
    from the point of view of the fixed object.
*/

#include <cmath>
#include "imager.h"

namespace Imager
{
    // Rotates counterclockwise around center looking into axis parallel to x-axis.
    SolidObject& SolidObject_Reorientable::RotateX(double angleInDegrees)    
    {
        const double angleInRadians = RadiansFromDegrees(angleInDegrees);
        const double a = cos(angleInRadians);
        const double b = sin(angleInRadians);

        rDir = Vector(rDir.x, a*rDir.y - b*rDir.z, a*rDir.z + b*rDir.y);
        sDir = Vector(sDir.x, a*sDir.y - b*sDir.z, a*sDir.z + b*sDir.y);
        tDir = Vector(tDir.x, a*tDir.y - b*tDir.z, a*tDir.z + b*tDir.y);

        UpdateInverseRotation();

        return *this;
    }

    // Rotates counterclockwise around center looking into axis parallel to y-axis.
    SolidObject& SolidObject_Reorientable::RotateY(double angleInDegrees)    
    {
        const double angleInRadians = RadiansFromDegrees(angleInDegrees);
        const double a = cos(angleInRadians);
        const double b = sin(angleInRadians);

        rDir = Vector(a*rDir.x + b*rDir.z, rDir.y, a*rDir.z - b*rDir.x);
        sDir = Vector(a*sDir.x + b*sDir.z, sDir.y, a*sDir.z - b*sDir.x);
        tDir = Vector(a*tDir.x + b*tDir.z, tDir.y, a*tDir.z - b*tDir.x);

        UpdateInverseRotation();

        return *this;
    }

    // Rotates counterclockwise around center looking into axis parallel to z-axis.
    SolidObject& SolidObject_Reorientable::RotateZ(double angleInDegrees)    
    {
        const double angleInRadians = RadiansFromDegrees(angleInDegrees);
        const double a = cos(angleInRadians);
        const double b = sin(angleInRadians);

        rDir = Vector(a*rDir.x - b*rDir.y, a*rDir.y + b*rDir.x, rDir.z);
        sDir = Vector(a*sDir.x - b*sDir.y, a*sDir.y + b*sDir.x, sDir.z);
        tDir = Vector(a*tDir.x - b*tDir.y, a*tDir.y + b*tDir.x, tDir.z);

        UpdateInverseRotation();

        return *this;
    }

    // Appends to 'intersectionList' a list of all the intersections 
    // found starting at the specified vantage point in the specified direction.
    void SolidObject_Reorientable::AppendAllIntersections(
        const Vector& vantage, 
        const Vector& direction, 
        IntersectionList& intersectionList) const
    {
        const Vector objectVantage = ObjectPointFromCameraPoint(vantage);
        const Vector objectRay     = ObjectDirFromCameraDir(direction);

        const size_t sizeBeforeAppend = intersectionList.size();

        ObjectSpace_AppendAllIntersections(
            objectVantage, 
            objectRay, 
            intersectionList
        );

        // Iterate only through the items we just appended,
        // skipping over anything that was already in the list
        // before this function was called.
        for (size_t index = sizeBeforeAppend; 
             index < intersectionList.size(); 
             ++index)
        {
            Intersection& intersection = intersectionList[index];

            // Need to transform intersection back into camera space.
            intersection.point = 
                CameraPointFromObjectPoint(intersection.point);

            intersection.surfaceNormal = 
                CameraDirFromObjectDir(intersection.surfaceNormal);
        }
    }
}