game_animation_programming/src/model.cpp

#include "model.h"
#include "logger.h"

bool load_model(Model *model, Render_Data *render_data, string model_filepath, string texture_filepath) {
  {
    bool success = load_texture(&model->texture, texture_filepath);
    if (!success) {
      log(1, "%s: failed to load texture\n", __FUNCTION__);
      return false;
    }
  }

  model->gltf_model = new tinygltf::Model();
  tinygltf::TinyGLTF gltf_loader;
  string loader_errors;
  string loader_warnings;
  bool result = false;
  result = gltf_loader.LoadASCIIFromFile(model->gltf_model, &loader_errors, &loader_warnings, model_filepath);

  if (!loader_warnings.empty()) {
    log(1, "%s: warnings while loading glTF model:\n%s", __FUNCTION__, loader_warnings.c_str());
  }

  if (!loader_errors.empty()) {
    log(1, "%s: errors while loading glTF model:\n%s", __FUNCTION__, loader_errors.c_str());
  }

  if (!result) {
    log(1, "%s error: could not load file '%s'\n", __FUNCTION__, model_filepath.c_str());
    return false;
  }

  glGenVertexArrays(1, &model->vao);
  glBindVertexArray(model->vao);

  create_model_vertex_buffers(model);
  create_model_index_buffer(model);

  glBindVertexArray(0);


  s32 root_node_id = model->gltf_model->scenes.at(0).nodes.at(0);
   create_root(model->root_node, root_node_id);
  

  render_data->triangle_count = get_model_triangle_count(model);

  return true;
}

void draw_model(Model *model) {
  const tinygltf::Primitive& primitives = model->gltf_model->meshes.at(0).primitives.at(0);
  const tinygltf::Accessor& index_accessor = model->gltf_model->accessors.at(primitives.indices);
  u32 draw_mode = GL_TRIANGLES;
  switch (primitives.mode) {
    case TINYGLTF_MODE_TRIANGLES:
      draw_mode = GL_TRIANGLES;
      break;
    default:
      log(1, "%s error: unknown draw mode %i\n", __FUNCTION__, draw_mode);
      break;
  }

  bind_texture(&model->texture);
  glBindVertexArray(model->vao);
  glDrawElements(draw_mode, index_accessor.count, index_accessor.componentType, nullptr);
  glBindVertexArray(0);
  unbind_texture();
}

void cleanup_model(Model *model) {
  glDeleteBuffers(model->vertex_vbo.size(), model->vertex_vbo.data());
  glDeleteBuffers(1, &model->vao);
  glDeleteBuffers(1, &model->index_vbo);
  cleanup_texture(&model->texture);
  delete model->gltf_model;
}

void create_model_vertex_buffers(Model *model) {
  const tinygltf::Primitive &primitives = model->gltf_model->meshes.at(0).primitives.at(0);
  model->vertex_vbo.resize(primitives.attributes.size());

  for (const auto& attrib : primitives.attributes) {
    const string attrib_type = attrib.first;
    const s32 accessor_num = attrib.second;
    const tinygltf::Accessor &accessor = model->gltf_model->accessors.at(accessor_num);
    const tinygltf::BufferView &buffer_view = model->gltf_model->bufferViews[accessor.bufferView];
    const tinygltf::Buffer &buffer = model->gltf_model->buffers[buffer_view.buffer];

    if ((attrib_type.compare("POSITION") != 0) &&
        (attrib_type.compare("NORMAL") != 0) &&
        (attrib_type.compare("TEXCOORD_0") != 0)) {
      log(1, "%s: skipping attribute type %s\n", __FUNCTION__, attrib_type.c_str());
      continue;
    }

    s32 data_size = 1;
    switch(accessor.type) {
      case TINYGLTF_TYPE_SCALAR:
        data_size = 1;
        break;
      case TINYGLTF_TYPE_VEC2:
        data_size = 2;
        break;
      case TINYGLTF_TYPE_VEC3:
        data_size = 3;
        break;        
      case TINYGLTF_TYPE_VEC4:
        data_size = 4;
        break;
      default:
        log(1, "%s error: accessor %i uses data size %i\n", __FUNCTION__, accessor_num, data_size);
        break;
    }

    u32 data_type = GL_FLOAT;
    switch(accessor.componentType) {
      case TINYGLTF_COMPONENT_TYPE_FLOAT:
        data_type = GL_FLOAT;
        break;
      default:
        log(1, "%s error: accessor %i uses unknown data type %i\n", __FUNCTION__, accessor_num, data_type);
        break;
    }

    glGenBuffers(1, &model->vertex_vbo.at(model->attributes.at(attrib_type)));
    glBindBuffer(GL_ARRAY_BUFFER, model->vertex_vbo.at(model->attributes.at(attrib_type)));

    glVertexAttribPointer(model->attributes.at(attrib_type), data_size, data_type, GL_FALSE, 0, (void*) 0);
    glEnableVertexAttribArray(model->attributes.at(attrib_type));
    glBindBuffer(GL_ARRAY_BUFFER, 0);
  }
}

void create_model_index_buffer(Model *model) {
  glGenBuffers(1, &model->index_vbo);
  glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, model->index_vbo);
}

void upload_model_vertex_buffers(Model *model) {  
  for (s32 i = 0; i < 3; ++i) {
    const tinygltf::Accessor& accessor = model->gltf_model->accessors.at(i);
    const tinygltf::BufferView& buffer_view = model->gltf_model->bufferViews.at(accessor.bufferView);
    const tinygltf::Buffer& buffer = model->gltf_model->buffers.at(buffer_view.buffer);
    glBindBuffer(GL_ARRAY_BUFFER, model->vertex_vbo[i]);
    glBufferData(GL_ARRAY_BUFFER, buffer_view.byteLength, &buffer.data.at(0) + buffer_view.byteOffset, GL_STATIC_DRAW);
    glBindBuffer(GL_ARRAY_BUFFER, 0);
  }
}

void upload_model_index_buffer(Model *model) {
  const tinygltf::Primitive& primitives = model->gltf_model->meshes.at(0).primitives.at(0);
  const tinygltf::Accessor& index_accessor = model->gltf_model->accessors.at(primitives.indices);
  const tinygltf::BufferView& index_buffer_view = model->gltf_model->bufferViews.at(index_accessor.bufferView);
  const tinygltf::Buffer& index_buffer = model->gltf_model->buffers.at(index_buffer_view.buffer);

  glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, model->index_vbo);
  glBufferData(GL_ELEMENT_ARRAY_BUFFER, index_buffer_view.byteLength, &index_buffer.data.at(0) + index_buffer_view.byteOffset, GL_STATIC_DRAW);
}

s32 get_model_triangle_count(Model *model) {
  const tinygltf::Primitive& primitives = model->gltf_model->meshes.at(0).primitives.at(0);
  const tinygltf::Accessor& index_accessor = model->gltf_model->accessors.at(primitives.indices);

  return index_accessor.count;
}