camera.cpp

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/*
 * Copyright (C) 2023  Christopher J. Howard
 *
 * This file is part of Antkeeper source code.
 *
 * Antkeeper source code 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 3 of the License, or
 * (at your option) any later version.
 *
 * Antkeeper source code 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 Antkeeper source code.  If not, see <http://www.gnu.org/licenses/>.
 */
 
#include <engine/scene/camera.hpp>
#include <engine/math/quaternion.hpp>
#include <engine/math/projection.hpp>
 
namespace scene {
 
geom::ray<float, 3> camera::pick(const math::fvec2& ndc) const
{
    const auto near = m_inv_view_projection * math::fvec4{ndc[0], ndc[1], 1.0f, 1.0f};
    const auto origin = math::fvec3(near) / near[3];
    const auto direction = math::normalize(origin - get_translation());
    
    return {origin, direction};
}
 
math::fvec3 camera::project(const math::fvec3& object, const math::fvec4& viewport) const
{
    math::fvec4 result = m_view_projection * math::fvec4{object[0], object[1], object[2], 1.0f};
    result /= result[3];
    
    result.x() = result.x() * viewport[2] + viewport[0];
    result.y() = result.y() * viewport[3] + viewport[1];
    
    return math::fvec3(result);
}
 
math::fvec3 camera::unproject(const math::fvec3& window, const math::fvec4& viewport) const
{
    math::fvec4 result;
    result[0] = ((window[0] - viewport[0]) / viewport[2]) * 2.0f - 1.0f;
    result[1] = ((window[1] - viewport[1]) / viewport[3]) * 2.0f - 1.0f;
    //result[2] = window[2] * 2.0f - 1.0f; z: [-1, 1]
    //result[2] = window[2]; // z: [0, 1]
    result[2] = 1.0f - window[2]; // z: [1, 0]
    result[3] = 1.0f;
    
    result = m_inv_view_projection * result;
 
    return math::fvec3(result) * (1.0f / result[3]);
}
 
void camera::set_perspective(float vertical_fov, float aspect_ratio, float near, float far)
{
    // Set projection mode to perspective
    m_orthographic = false;
    
    // Update perspective projection parameters
    m_vertical_fov = vertical_fov;
    m_aspect_ratio = aspect_ratio;
    m_clip_near = near;
    m_clip_far = far;
    
    // Recalculate projection matrix (reversed depth) and its inverse
    if (m_clip_far == std::numeric_limits<float>::infinity())
    {
        std::tie(m_projection, m_inv_projection) = math::inf_perspective_half_z_reverse_inv(m_vertical_fov, m_aspect_ratio, m_clip_near);
    }
    else
    {
        std::tie(m_projection, m_inv_projection) = math::perspective_half_z_inv(m_vertical_fov, m_aspect_ratio, m_clip_far, m_clip_near);
    }
    
    // Recalculate view-projection matrix
    m_view_projection = m_projection * m_view;
    m_inv_view_projection = m_inv_view * m_inv_projection;
    
    // Recalculate view frustum
    update_frustum();
}
 
void camera::set_vertical_fov(float vertical_fov)
{
    if (!m_orthographic)
    {
        set_perspective(vertical_fov, m_aspect_ratio, m_clip_near, m_clip_far);
    }
}
 
void camera::set_aspect_ratio(float aspect_ratio)
{
    if (!m_orthographic)
    {
        set_perspective(m_vertical_fov, aspect_ratio, m_clip_near, m_clip_far);
    }
}
 
void camera::set_orthographic(float clip_left, float clip_right, float clip_bottom, float clip_top, float clip_near, float clip_far)
{
    // Set projection mode to orthographic
    m_orthographic = true;
    
    // Update signed distances to clipping planes
    m_clip_left = clip_left;
    m_clip_right = clip_right;
    m_clip_bottom = clip_bottom;
    m_clip_top = clip_top;
    m_clip_near = clip_near;
    m_clip_far = clip_far;
    
    // Recalculate projection matrix (reversed depth) and its inverse
    std::tie(m_projection, m_inv_projection) = math::ortho_half_z_inv(m_clip_left, m_clip_right, m_clip_bottom, m_clip_top, m_clip_far, m_clip_near);
    
    // Update view-projection matrix and its inverse
    m_view_projection = m_projection * m_view;
    m_inv_view_projection = m_inv_view * m_inv_projection;
    
    // Update view frustum
    update_frustum();
}
 
void camera::set_exposure_value(float ev100)
{
    m_exposure_value = ev100;
    // m_exposure_normalization = 1.0f / (std::exp2(m_exposure_value) * 1.2f);
    m_exposure_normalization = 1.0f / (std::exp2(m_exposure_value));
}
 
void camera::transformed()
{
    // Update basis vectors
    m_forward = get_rotation() * math::fvec3{0.0f, 0.0f, -1.0f};
    m_up = get_rotation() * math::fvec3{0.0f, 1.0f, 0.0f};
    
    // Recalculate view matrix and its inverse
    std::tie(m_view, m_inv_view) = math::look_at_rh_inv(get_translation(), get_translation() + m_forward, m_up);
    
    // Update view-projection matrix and its inverse
    m_view_projection = m_projection * m_view;
    m_inv_view_projection = m_inv_view * m_inv_projection;
    
    // Update view frustum
    update_frustum();
}
 
void camera::update_frustum()
{
    // Recalculate view frustum
    m_view_frustum.extract(m_view_projection);
    
    // Reverse half z clip-space coordinates of a cube
    constexpr math::fvec4 clip_space_cube[8] =
    {
        {-1, -1, 1, 1}, // NBL
        { 1, -1, 1, 1}, // NBR
        {-1,  1, 1, 1}, // NTL
        { 1,  1, 1, 1}, // NTR
        {-1, -1, 0, 1}, // FBL
        { 1, -1, 0, 1}, // FBR
        {-1,  1, 0, 1}, // FTL
        { 1,  1, 0, 1}  // FTR
    };
    
    // Update bounds
    m_bounds = {math::fvec3::infinity(), -math::fvec3::infinity()};
    for (std::size_t i = 0; i < 8; ++i)
    {
        const math::fvec4 frustum_corner = m_inv_view_projection * clip_space_cube[i];
        m_bounds.extend(math::fvec3(frustum_corner) / frustum_corner[3]);
    }
}
 
} // namespace scene