model.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/render/model.hpp>
#include <engine/resources/resource-loader.hpp>
#include <engine/resources/resource-manager.hpp>
#include <engine/render/vertex-attribute-location.hpp>
#include <engine/math/numbers.hpp>
#include <engine/utility/hash/fnv1a.hpp>
#include <bit>
#include <cstdint>
 
inline constexpr std::uint16_t vertex_attribute_position     = 0b0000000000000001;
inline constexpr std::uint16_t vertex_attribute_uv           = 0b0000000000000010;
inline constexpr std::uint16_t vertex_attribute_normal       = 0b0000000000000100;
inline constexpr std::uint16_t vertex_attribute_tangent      = 0b0000000000001000;
inline constexpr std::uint16_t vertex_attribute_color        = 0b0000000000010000;
inline constexpr std::uint16_t vertex_attribute_bone_index   = 0b0000000000100000;
inline constexpr std::uint16_t vertex_attribute_bone_weight  = 0b0000000001000000;
inline constexpr std::uint16_t vertex_attribute_morph_target = 0b0000000010000000;
 
template <>
std::unique_ptr<render::model> resource_loader<render::model>::load(::resource_manager& resource_manager, deserialize_context& ctx)
{
    // Read vertex format
    std::uint16_t vertex_format_flags = 0;
    ctx.read16<std::endian::little>(reinterpret_cast<std::byte*>(&vertex_format_flags), 1);
    
    // Read bones per vertex (if any)
    std::uint8_t bones_per_vertex = 0;
    if ((vertex_format_flags & vertex_attribute_bone_index) || (vertex_format_flags & vertex_attribute_bone_weight))
    {
        ctx.read8(reinterpret_cast<std::byte*>(&bones_per_vertex), 1);
    }
    
    // Read vertex count
    std::uint32_t vertex_count = 0;
    ctx.read32<std::endian::little>(reinterpret_cast<std::byte*>(&vertex_count), 1);
    
    // Determine vertex stride
    std::size_t vertex_stride = 0;
    if (vertex_format_flags & vertex_attribute_position)
    {
        vertex_stride += sizeof(float) * 3;
    }
    if (vertex_format_flags & vertex_attribute_uv)
    {
        vertex_stride += sizeof(float) * 2;
    }
    if (vertex_format_flags & vertex_attribute_normal)
    {
        vertex_stride += sizeof(float) * 3;
    }
    if (vertex_format_flags & vertex_attribute_tangent)
    {
        vertex_stride += sizeof(float) * 4;
    }
    if (vertex_format_flags & vertex_attribute_color)
    {
        vertex_stride += sizeof(float) * 4;
    }
    if (vertex_format_flags & vertex_attribute_bone_index)
    {
        vertex_stride += sizeof(std::uint16_t) * bones_per_vertex;
    }
    if (vertex_format_flags & vertex_attribute_bone_weight)
    {
        vertex_stride += sizeof(float) * bones_per_vertex;
    }
    if (vertex_format_flags & vertex_attribute_morph_target)
    {
        vertex_stride += sizeof(float) * 3;
    }
    
    // Allocate vertex data
    std::vector<std::byte> vertex_data(vertex_count * vertex_stride);
    
    // Read vertices
    if constexpr (std::endian::native == std::endian::little)
    {
        ctx.read8(vertex_data.data(), vertex_count * vertex_stride);
    }
    else
    {
        std::byte* vertex_data_offset = vertex_data.data();
        for (std::uint32_t i = 0; i < vertex_count; ++i)
        {
            if (vertex_format_flags & vertex_attribute_position)
            {
                ctx.read32<std::endian::little>(vertex_data_offset, 3);
                vertex_data_offset += sizeof(float) * 3;
            }
            if (vertex_format_flags & vertex_attribute_uv)
            {
                ctx.read32<std::endian::little>(vertex_data_offset, 2);
                vertex_data_offset += sizeof(float) * 2;
            }
            if (vertex_format_flags & vertex_attribute_normal)
            {
                ctx.read32<std::endian::little>(vertex_data_offset, 3);
                vertex_data_offset += sizeof(float) * 3;
            }
            if (vertex_format_flags & vertex_attribute_tangent)
            {
                ctx.read32<std::endian::little>(vertex_data_offset, 4);
                vertex_data_offset += sizeof(float) * 4;
            }
            if (vertex_format_flags & vertex_attribute_color)
            {
                ctx.read32<std::endian::little>(vertex_data_offset, 4);
                vertex_data_offset += sizeof(float) * 4;
            }
            if (vertex_format_flags & vertex_attribute_bone_index)
            {
                ctx.read16<std::endian::little>(vertex_data_offset, bones_per_vertex);
                vertex_data_offset += sizeof(std::uint16_t) * bones_per_vertex;
            }
            if (vertex_format_flags & vertex_attribute_bone_weight)
            {
                ctx.read32<std::endian::little>(vertex_data_offset, bones_per_vertex);
                vertex_data_offset += sizeof(float) * bones_per_vertex;
            }
            if (vertex_format_flags & vertex_attribute_morph_target)
            {
                ctx.read32<std::endian::little>(vertex_data_offset, 3);
                vertex_data_offset += sizeof(float) * 3;
            }
        }
    }
    
    // Allocate model
    std::unique_ptr<render::model> model = std::make_unique<render::model>();
    
    // Build model vertex buffer
    model->get_vertex_buffer() = std::make_shared<gl::vertex_buffer>(gl::buffer_usage::static_draw, vertex_data);
    model->set_vertex_offset(0);
    model->set_vertex_stride(vertex_stride);
    
    // Free vertex data
    vertex_data.clear();
    
    // Build vertex input attributes
    std::vector<gl::vertex_input_attribute> attributes(std::popcount(vertex_format_flags));
    
    std::uint32_t vertex_offset = 0;
    std::uint32_t attribute_index = 0;
    
    if (vertex_format_flags & vertex_attribute_position)
    {
        auto& attribute = attributes[attribute_index];
        attribute.location = render::vertex_attribute_location::position;
        attribute.binding = 0;
        attribute.format = gl::format::r32g32b32_sfloat;
        attribute.offset = vertex_offset;
        
        vertex_offset += 3 * sizeof(float);
        ++attribute_index;
    }
    if (vertex_format_flags & vertex_attribute_uv)
    {
        auto& attribute = attributes[attribute_index];
        attribute.location = render::vertex_attribute_location::uv;
        attribute.binding = 0;
        attribute.format = gl::format::r32g32_sfloat;
        attribute.offset = vertex_offset;
        
        vertex_offset += 2 * sizeof(float);
        ++attribute_index;
    }
    if (vertex_format_flags & vertex_attribute_normal)
    {
        auto& attribute = attributes[attribute_index];
        attribute.location = render::vertex_attribute_location::normal;
        attribute.binding = 0;
        attribute.format = gl::format::r32g32b32_sfloat;
        attribute.offset = vertex_offset;
        
        vertex_offset += 3 * sizeof(float);
        ++attribute_index;
    }
    if (vertex_format_flags & vertex_attribute_tangent)
    {
        auto& attribute = attributes[attribute_index];
        attribute.location = render::vertex_attribute_location::tangent;
        attribute.binding = 0;
        attribute.format = gl::format::r32g32b32a32_sfloat;
        attribute.offset = vertex_offset;
        
        vertex_offset += 4 * sizeof(float);
        ++attribute_index;
    }
    if (vertex_format_flags & vertex_attribute_color)
    {
        auto& attribute = attributes[attribute_index];
        attribute.location = render::vertex_attribute_location::color;
        attribute.binding = 0;
        attribute.format = gl::format::r32g32b32a32_sfloat;
        attribute.offset = vertex_offset;
        
        vertex_offset += 4 * sizeof(float);
        ++attribute_index;
    }
    if (vertex_format_flags & vertex_attribute_bone_index)
    {
        auto& attribute = attributes[attribute_index];
        attribute.location = render::vertex_attribute_location::bone_index;
        attribute.binding = 0;
        switch (bones_per_vertex)
        {
            case 1:
                attribute.format = gl::format::r16_uint;
                break;
            case 2:
                attribute.format = gl::format::r16g16_uint;
                break;
            case 3:
                attribute.format = gl::format::r16g16b16_uint;
                break;
            case 4:
                attribute.format = gl::format::r16g16b16a16_uint;
                break;
            default:
                attribute.format = gl::format::undefined;
                break;
        }
        attribute.offset = vertex_offset;
        
        vertex_offset += bones_per_vertex * sizeof(std::uint16_t);
        ++attribute_index;
    }
    if (vertex_format_flags & vertex_attribute_bone_weight)
    {
        auto& attribute = attributes[attribute_index];
        attribute.location = render::vertex_attribute_location::bone_weight;
        attribute.binding = 0;
        switch (bones_per_vertex)
        {
            case 1:
                attribute.format = gl::format::r32_sfloat;
                break;
            case 2:
                attribute.format = gl::format::r32g32_sfloat;
                break;
            case 3:
                attribute.format = gl::format::r32g32b32_sfloat;
                break;
            case 4:
                attribute.format = gl::format::r32g32b32a32_sfloat;
                break;
            default:
                attribute.format = gl::format::undefined;
                break;
        }
        attribute.offset = vertex_offset;
        
        vertex_offset += bones_per_vertex * sizeof(float);
        ++attribute_index;
    }
    if (vertex_format_flags & vertex_attribute_morph_target)
    {
        auto& attribute = attributes[attribute_index];
        attribute.location = render::vertex_attribute_location::target;
        attribute.binding = 0;
        attribute.format = gl::format::r32g32b32_sfloat;
        attribute.offset = vertex_offset;
        
        // vertex_offset += 3 * sizeof(float);
        // ++attribute_index;
    }
    
    // Build model vertex array
    model->get_vertex_array() = std::make_shared<gl::vertex_array>(attributes);
    
    // Read model bounds
    ctx.read32<std::endian::little>(reinterpret_cast<std::byte*>(&model->get_bounds()), 6);
    
    // Read material count
    std::uint16_t material_count = 0;
    ctx.read16<std::endian::little>(reinterpret_cast<std::byte*>(&material_count), 1);
    
    // Allocate material groups
    model->get_groups().resize(material_count);
    
    // Read materials
    for (auto& group: model->get_groups())
    {
        // Read material name length
        std::uint8_t material_name_length = 0;
        ctx.read8(reinterpret_cast<std::byte*>(&material_name_length), 1);
        
        // Read material name
        std::string material_name(static_cast<std::size_t>(material_name_length), '\0');
        ctx.read8(reinterpret_cast<std::byte*>(material_name.data()), material_name_length);
        
        // Generate group ID by hashing material name
        group.id = hash::fnv1a32<char>(material_name);
        
        // Set group primitive topology
        group.primitive_topology = gl::primitive_topology::triangle_list;
        
        // Read index of first vertex
        ctx.read32<std::endian::little>(reinterpret_cast<std::byte*>(&group.first_vertex), 1);
        
        // Read vertex count
        ctx.read32<std::endian::little>(reinterpret_cast<std::byte*>(&group.vertex_count), 1);
        
        // Slugify material filename
        std::string material_filename = material_name + ".mtl";
        std::replace(material_filename.begin(), material_filename.end(), '_', '-');
        
        // Load group material
        group.material = resource_manager.load<render::material>(material_filename);
    }
    
    // Read skeleton
    if ((vertex_format_flags & vertex_attribute_bone_index) || (vertex_format_flags & vertex_attribute_bone_weight))
    {
        ::skeleton& skeleton = model->get_skeleton();
        
        // Read bone count
        std::uint16_t bone_count = 0;
        ctx.read16<std::endian::little>(reinterpret_cast<std::byte*>(&bone_count), 1);
        
        // Resize skeleton
        skeleton.add_bones(bone_count);
        
        // Read bones
        for (std::uint16_t i = 0; i < bone_count; ++i)
        {
            // Read bone name
            hash::fnv1a32_t bone_name = {};
            ctx.read32<std::endian::little>(reinterpret_cast<std::byte*>(&bone_name), 1);
            
            // Read bone parent index
            std::uint16_t bone_parent_index = i;
            ctx.read16<std::endian::little>(reinterpret_cast<std::byte*>(&bone_parent_index), 1);
            
            // Construct bone transform
            bone_transform_type bone_transform;
            
            // Read bone translation
            ctx.read32<std::endian::little>(reinterpret_cast<std::byte*>(bone_transform.translation.data()), 3);
            
            // Read bone rotation
            ctx.read32<std::endian::little>(reinterpret_cast<std::byte*>(&bone_transform.rotation.r), 1);
            ctx.read32<std::endian::little>(reinterpret_cast<std::byte*>(bone_transform.rotation.i.data()), 3);
            
            // Set bone scale
            bone_transform.scale = {1, 1, 1};
            
            // Read bone length
            float bone_length = 0.0f;
            ctx.read32<std::endian::little>(reinterpret_cast<std::byte*>(&bone_length), 1);
            
            // Set bone properties
            skeleton.set_bone_name(i, bone_name);
            skeleton.set_bone_parent(i, bone_parent_index);
            skeleton.set_bone_transform(i, bone_transform);
        }
        
        // Update skeleton's rest pose
        skeleton.update_rest_pose();
    }
    
    return model;
}