bloom-pass.cpp

Go to the documentation of this file.

/*
 * 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/render/passes/bloom-pass.hpp>
#include <engine/resources/resource-manager.hpp>
#include <engine/gl/pipeline.hpp>
#include <engine/gl/framebuffer.hpp>
#include <engine/gl/shader-program.hpp>
#include <engine/gl/shader-variable.hpp>
#include <engine/gl/vertex-buffer.hpp>
#include <engine/gl/vertex-array.hpp>
#include <engine/gl/texture.hpp>
#include <engine/render/vertex-attribute-location.hpp>
#include <engine/render/context.hpp>
#include <algorithm>
#include <cmath>
 
namespace render {
 
bloom_pass::bloom_pass(gl::pipeline* pipeline, resource_manager* resource_manager):
    pass(pipeline, nullptr)
{
    // Load downsample shader template
    auto downsample_shader_template = resource_manager->load<gl::shader_template>("bloom-downsample.glsl");
    
    // Build downsample shader program with Karis averaging
    m_downsample_karis_shader = downsample_shader_template->build
    (
        {
            {"KARIS_AVERAGE", std::string()}
        }
    );
    
    // Build downsample shader program without Karis averaging
    m_downsample_shader = downsample_shader_template->build();
    
    // Load upsample shader template
    auto upsample_shader_template = resource_manager->load<gl::shader_template>("bloom-upsample.glsl");
    
    // Build upsample shader program
    m_upsample_shader = upsample_shader_template->build();
    
    // Construct framebuffer texture sampler
    m_sampler = std::make_shared<gl::sampler>
    (
        gl::sampler_filter::linear,
        gl::sampler_filter::linear,
        gl::sampler_mipmap_mode::linear,
        gl::sampler_address_mode::clamp_to_edge,
        gl::sampler_address_mode::clamp_to_edge
    );
    
    // Allocate empty vertex array
    m_vertex_array = std::make_unique<gl::vertex_array>();
}
 
void bloom_pass::render(render::context& ctx)
{
    // Execute command buffer
    for (const auto& command: m_command_buffer)
    {
        command();
    }
}
 
void bloom_pass::set_source_texture(std::shared_ptr<gl::texture_2d> texture)
{
    if (m_source_texture != texture)
    {
        m_source_texture = texture;
        
        rebuild_mip_chain();
        correct_filter_radius();
        rebuild_command_buffer();
    }
}
 
void bloom_pass::set_mip_chain_length(unsigned int length)
{   
    m_mip_chain_length = length;
    rebuild_mip_chain();
    rebuild_command_buffer();
}
 
void bloom_pass::set_filter_radius(float radius)
{
    m_filter_radius = radius;
    correct_filter_radius();
}
 
void bloom_pass::rebuild_mip_chain()
{
    if (m_source_texture && m_mip_chain_length)
    {
        // Rebuild target image
        m_target_image = std::make_shared<gl::image_2d>
        (
            gl::format::r16g16b16_sfloat,
            m_source_texture->get_image_view()->get_image()->get_dimensions()[0],
            m_source_texture->get_image_view()->get_image()->get_dimensions()[1],
            m_mip_chain_length
        );
        
        m_target_textures.resize(m_mip_chain_length);
        m_target_framebuffers.resize(m_mip_chain_length);
        for (unsigned int i = 0; i < m_mip_chain_length; ++i)
        {
            // Rebuild mip texture
            m_target_textures[i] = std::make_shared<gl::texture_2d>
            (
                std::make_shared<gl::image_view_2d>
                (
                    m_target_image,
                    m_target_image->get_format(),
                    i,
                    1
                ),
                m_sampler
            );
            
            // Rebuild mip framebuffer
            const gl::framebuffer_attachment attachments[1] =
            {{
                gl::color_attachment_bit,
                m_target_textures[i]->get_image_view(),
                0
            }};
            m_target_framebuffers[i] = std::make_shared<gl::framebuffer>
            (
                attachments,
                m_target_image->get_dimensions()[0] >> i,
                m_target_image->get_dimensions()[1] >> i
            );
        }
    }
    else
    {
        m_target_image = nullptr;
        m_target_textures.clear();
        m_target_framebuffers.clear();
    }
}
 
void bloom_pass::correct_filter_radius()
{
    // Get aspect ratio of target image
    float aspect_ratio = 1.0f;
    if (m_target_image)
    {
        aspect_ratio = static_cast<float>(m_target_image->get_dimensions()[1]) /
            static_cast<float>(m_target_image->get_dimensions()[0]);
    }
    
    // Correct filter radius according to target image aspect ratio
    m_corrected_filter_radius = {m_filter_radius * aspect_ratio, m_filter_radius};
}
 
void bloom_pass::rebuild_command_buffer()
{
    m_command_buffer.clear();
    
    if (!m_source_texture ||
        !m_mip_chain_length ||
        !m_downsample_karis_shader ||
        !m_downsample_shader ||
        !m_upsample_shader)
    {
        return;
    }
    
    // Setup downsample state
    m_command_buffer.emplace_back
    (
        [&]()
        {
            m_pipeline->set_primitive_topology(gl::primitive_topology::triangle_list);
            m_pipeline->bind_vertex_array(m_vertex_array.get());
            m_pipeline->set_depth_test_enabled(false);
            m_pipeline->set_cull_mode(gl::cull_mode::back);
            m_pipeline->set_color_blend_enabled(false);
        }
    );
    
    // Downsample first mip with Karis average
    if (auto source_texture_var = m_downsample_karis_shader->variable("source_texture"))
    {
        m_command_buffer.emplace_back
        (
            [&, source_texture_var]()
            {
                m_pipeline->bind_shader_program(m_downsample_karis_shader.get());
                m_pipeline->bind_framebuffer(m_target_framebuffers[0].get());
                
                const auto& target_dimensions = m_target_image->get_dimensions();
                const gl::viewport viewport[1] = {{0.0f, 0.0f, static_cast<float>(target_dimensions[0]), static_cast<float>(target_dimensions[1])}};
                m_pipeline->set_viewport(0, viewport);
                
                source_texture_var->update(*m_source_texture);
                
                // Draw fullscreen triangle
                m_pipeline->draw(3, 1, 0, 0);
            }
        );
    }
    
    // Downsample remaining mips
    if (m_mip_chain_length > 1)
    {
        if (auto source_texture_var = m_downsample_shader->variable("source_texture"))
        {
            m_command_buffer.emplace_back([&](){m_pipeline->bind_shader_program(m_downsample_shader.get());});
            
            for (int i = 1; i < static_cast<int>(m_mip_chain_length); ++i)
            {
                m_command_buffer.emplace_back
                (
                    [&, source_texture_var, i]()
                    {
                        m_pipeline->bind_framebuffer(m_target_framebuffers[i].get());
                        
                        const auto& target_dimensions = m_target_image->get_dimensions();
                        const gl::viewport viewport[1] = {{0.0f, 0.0f, static_cast<float>(target_dimensions[0] >> i), static_cast<float>(target_dimensions[1] >> i)}};
                        m_pipeline->set_viewport(0, viewport);
                        
                        // Use previous downsample texture as downsample source
                        source_texture_var->update(*m_target_textures[i - 1]);
                        
                        // Draw fullscreen triangle
                        m_pipeline->draw(3, 1, 0, 0);
                    }
                );
            }
        }
    }
    
    // Setup upsample state
    m_command_buffer.emplace_back
    (
        [&]()
        {
            // Enable additive blending
            m_pipeline->set_color_blend_enabled(true);
            m_pipeline->set_color_blend_equation
            ({
                gl::blend_factor::one,
                gl::blend_factor::one,
                gl::blend_op::add,
                gl::blend_factor::one,
                gl::blend_factor::one,
                gl::blend_op::add
            });
            
            // Bind upsample shader
            m_pipeline->bind_shader_program(m_upsample_shader.get());
        }
    );
    
    // Update upsample filter radius
    if (auto filter_radius_var = m_upsample_shader->variable("filter_radius"))
    {
        m_command_buffer.emplace_back([&, filter_radius_var](){filter_radius_var->update(m_corrected_filter_radius);});
    }
    
    // Upsample
    if (auto source_texture_var = m_upsample_shader->variable("source_texture"))
    {
        for (int i = static_cast<int>(m_mip_chain_length) - 1; i > 0; --i)
        {
            const int j = i - 1;
            
            m_command_buffer.emplace_back
            (
                [&, source_texture_var, i, j]()
                {
                    m_pipeline->bind_framebuffer(m_target_framebuffers[j].get());
                    
                    const auto& target_dimensions = m_target_image->get_dimensions();
                    const gl::viewport viewport[1] = {{0.0f, 0.0f, static_cast<float>(target_dimensions[0] >> j), static_cast<float>(target_dimensions[1] >> j)}};
                    m_pipeline->set_viewport(0, viewport);
                    
                    source_texture_var->update(*m_target_textures[i]);
                    
                    // Draw fullscreen triangle
                    m_pipeline->draw(3, 1, 0, 0);
                }
            );
        }
    }
}
 
} // namespace render