thinlenscamera.cpp

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/*
    toxic - A Global Illumination Renderer
    Copyright (C) 2003-2004 Francois Beaune
    Contact: http://toxicengine.sourceforge.net/

    This file is part of toxic.

    toxic is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    toxic is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with toxic; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

#include "thinlenscamera.h" // include first
#include "common/math/sampling.h"
#include "context.h"
#include "ray.h"
#include "scene.h"

#include <cassert>
#include <cmath>

using namespace sheep;
using namespace toxic;

ThinLensCamera::ThinLensCamera(const Matrix4 &m,
                               Real hfov,
                               Real aspect_ratio,
                               Real fstop,
                               Real focal_length,
                               Real focal_distance) :
    ICamera(m, hfov, aspect_ratio)
{
    // Compute camera lens radius.
    assert(fstop > 0.0);
    assert(focal_length >= 0.0);
    m_lens_radius = 0.5 * focal_length / fstop;

    // Set camera focal distance.
    m_af_enabled = false;
    assert(focal_distance >= 0.0);
    m_focal_distance = focal_distance;
}

ThinLensCamera::ThinLensCamera(const Matrix4 &m,
                               Real hfov,
                               Real aspect_ratio,
                               Real fstop,
                               Real focal_length,
                               const Point2 &af_target) :
    ICamera(m, hfov, aspect_ratio)
{
    // Compute camera lens radius.
    assert(fstop > 0.0);
    assert(focal_length >= 0.0);
    m_lens_radius = 0.5 * focal_length / fstop;

    // Camera focal distance will be computed by the autofocus
    // mechanism in the Finalize() method.
    assert(af_target.m_x >= -0.5 && af_target.m_x <= 0.5);
    assert(af_target.m_y >= -0.5 && af_target.m_y <= 0.5);
    m_af_enabled = true;
    m_af_target = af_target;
}

void ThinLensCamera::Finalize(const Context &context,
                              const Scene *scene)
{
    if(m_af_enabled) {
        // Create a ray with origin at the lens center and directed toward the
        // specified location on the film plane.
        Ray ray(Ray::AUTOFOCUS_RAY);
        ray.m_origin = m_location;
        ray.m_direction =
            m_af_target.m_x * m_u +     // m_u = m_ex * m_aspect_ratio
            m_af_target.m_y * m_ey +
            m_w;                        // m_w = m_ez * (-m_focal_length)
        ray.m_direction.Normalize();

        // Cast a ray through the scene to compute focal distance. If the ray
        // don't hit any object, throw an exception.
        Hit hit;
        if(scene->Trace(context, ray, &hit))
            m_focal_distance = hit.m_abscissa;
        else {
            assert(!"Could not compute focal distance.");
            throw "Could not compute focal distance.";
        }
    }
}

Ray ThinLensCamera::ComputeRay(const Context &context,
                               const Point2 &p) const
{
    assert(p.m_x >= -0.5 && p.m_x <= 0.5);
    assert(p.m_y >= -0.5 && p.m_y <= 0.5);

    // Create a ray with origin at the lens center and directed toward
    // the specified location on the film plane.
    Ray ray(Ray::PRIMARY_RAY);
    ray.m_origin = m_location;
    ray.m_direction =
        p.m_x * m_u +   // m_u = m_ex * m_aspect_ratio
        p.m_y * m_ey +
        m_w;            // m_w = m_ez * (-m_focal_length)
    ray.m_direction.Normalize();

    // Intersect the ray with the focal plane (the plane of focus).
    const Real t = -m_focal_distance / (ray.m_direction * m_ez);
    assert(t >= 0.0);
    const Point3 pt_on_fp = ray.GetPointAt(t);

    // Randomly choose a location on the lens surface (the lens surface
    // is approximated by a disk: this is the thin lens approximation).
    const Real xi1 = context.m_rng->RandomReal1();
    const Real xi2 = context.m_rng->RandomReal1();
    const Vector2 lens_sample = m_lens_radius * UniformDiskSampling(xi1, xi2);

    // Shift origin of the ray.
    ray.m_origin +=
        lens_sample.m_x * m_ex +
        lens_sample.m_y * m_ey;

    // Compute new direction of the ray.
    ray.m_direction = (pt_on_fp - ray.m_origin).Normalized();

    return ray;
}

Point2 ThinLensCamera::Project(const Point3 &p) const {
    Vector3 xi = p - m_location;
    assert(xi * m_ez != 0.0);

    xi *= -m_focal_length / (xi * m_ez);

    return Point2(xi * m_ex / m_aspect_ratio, xi * m_ey);
}

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