camera.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 "camera.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;

Camera::Camera(const Matrix4 &m,
               Real hfov /*= DEFAULT_CAMERA_FOV*/,
               Real aspect_ratio /*= DEFAULT_CAMERA_ASPECT_RATIO*/) :
    Basis(m),
    m_location(TransformToWorld(Point3(0.0))),
    m_ex(TransformToWorld(Vector3(1.0, 0.0, 0.0))),
    m_ey(TransformToWorld(Vector3(0.0, 1.0, 0.0))),
    m_ez(TransformToWorld(Vector3(0.0, 0.0, 1.0))),
    m_hfov(hfov),
    m_aspect_ratio(aspect_ratio),
    m_is_dof_enabled(false),
    m_dof_fstop(0.0),
    m_dof_focal_length(0.0),
    m_dof_focal_distance(0.0),
    m_dof_lens_radius(0.0),
    m_is_autofocus_enabled(false),
    m_autofocus_target(Point2(0.0))
{
    assert(m_hfov > -PI && m_hfov < PI);

    m_focal_length = m_aspect_ratio / tan(0.5 * m_hfov);

    m_u = m_ex * m_aspect_ratio;
    m_w = m_ez * (-m_focal_length);
}

void Camera::Finalize(const Context &context, const Scene *scene) {
    if(m_is_autofocus_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_autofocus_target.m_x * m_u +  // m_u = m_ex * m_aspect_ratio
            m_autofocus_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, focal distance is not altered.
        Hit hit;
        if(scene->Trace(context, ray, &hit))
            m_dof_focal_distance = hit.m_abscissa;
    }
}

void Camera::EnableDepthOfField(Real fstop, Real focal_length, Real focal_distance) {
    assert(fstop > 0.0);
    assert(focal_length >= 0.0);
    assert(focal_distance >= 0.0);

    m_is_dof_enabled = true;
    m_dof_fstop = fstop;
    m_dof_focal_length = focal_length;
    m_dof_focal_distance = focal_distance;

    // Compute lens radius.
    m_dof_lens_radius = 0.5 * m_dof_focal_length / m_dof_fstop;
}

void Camera::EnableAutoFocus(const Point2 &p) {
    assert(p.m_x >= -0.5 && p.m_x <= 0.5);
    assert(p.m_y >= -0.5 && p.m_y <= 0.5);

    m_is_autofocus_enabled = true;
    m_autofocus_target = p;
}

Ray Camera::ComputeRay(const Context &context, const Point2 &p) const { //!< Returned ray is expressed in world space.
    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 starting 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();

    if(m_is_dof_enabled) {
        // Intersect the ray with the focal plane (the plane of focus).
        const Real t = -m_dof_focal_distance / (ray.m_direction * m_ez);
        assert(t >= 0.0);
        const Point3 p = ray.GetPointAt(t);

        // Randomly choose a location on the lens surface (note: we're under the thin lens approximation).
        const Real xi1 = context.m_rng->RandomReal1();
        const Real xi2 = context.m_rng->RandomReal1();
        const Vector2 lens_sample = m_dof_lens_radius * UniformDiskSampling(xi1, xi2);

        // Update ray's origin.
        ray.m_origin +=
            lens_sample.m_x * m_ex +
            lens_sample.m_y * m_ey;

        // Update ray's direction.
        ray.m_direction = (p - ray.m_origin).Normalized();
    }

    assert(ray.m_direction.IsUnitLength());

    return ray;
}

Point2 Camera::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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