3d_model.cpp

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/*
 * This program source code file is part of KiCad, a free EDA CAD application.
 *
 * Copyright (C) 2020 Oleg Endo <[email protected]>
 * Copyright (C) 2015-2020 Mario Luzeiro <[email protected]>
 * Copyright (C) 2015-2020 KiCad Developers, see AUTHORS.txt for contributors.
 *
 * This program 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.
 *
 * This program 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 this program; if not, you may find one here:
 * http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 * or you may search the http://www.gnu.org website for the version 2 license,
 * or you may write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
 */
 
#include <algorithm>
#include <stdexcept>
#include <gal/opengl/kiglew.h> // Must be included first
 
#include "3d_model.h"
#include "../common_ogl/ogl_utils.h"
#include "../3d_math.h"
#include <utility>
#include <wx/debug.h>
#include <wx/log.h>
#include <chrono>
#include <memory>
 
 
/*
 * Flag to enable connectivity profiling.
 *
 * @ingroup trace_env_vars
 */
const wxChar* MODEL_3D::m_logTrace = wxT( "KI_TRACE_EDA_OGL_3DMODEL" );
 
 
void MODEL_3D::MakeBbox( const BBOX_3D& aBox, unsigned int aIdxOffset, VERTEX* aVtxOut,
 GLuint* aIdxOut, const glm::vec4& aColor )
{
 aVtxOut[0].m_pos = { aBox.Min().x, aBox.Min().y, aBox.Min().z };
 aVtxOut[1].m_pos = { aBox.Max().x, aBox.Min().y, aBox.Min().z };
 aVtxOut[2].m_pos = { aBox.Max().x, aBox.Max().y, aBox.Min().z };
 aVtxOut[3].m_pos = { aBox.Min().x, aBox.Max().y, aBox.Min().z };
 
 aVtxOut[4].m_pos = { aBox.Min().x, aBox.Min().y, aBox.Max().z };
 aVtxOut[5].m_pos = { aBox.Max().x, aBox.Min().y, aBox.Max().z };
 aVtxOut[6].m_pos = { aBox.Max().x, aBox.Max().y, aBox.Max().z };
 aVtxOut[7].m_pos = { aBox.Min().x, aBox.Max().y, aBox.Max().z };
 
 for( unsigned int i = 0; i < 8; ++i )
 aVtxOut[i].m_color = aVtxOut[i].m_cad_color = glm::clamp( aColor * 255.0f, 0.0f, 255.0f );
 
 #define bbox_line( vtx_a, vtx_b )\
 do { *aIdxOut++ = vtx_a + aIdxOffset; \
 *aIdxOut++ = vtx_b + aIdxOffset; } while( 0 )
 
 bbox_line( 0, 1 );
 bbox_line( 1, 2 );
 bbox_line( 2, 3 );
 bbox_line( 3, 0 );
 
 bbox_line( 4, 5 );
 bbox_line( 5, 6 );
 bbox_line( 6, 7 );
 bbox_line( 7, 4 );
 
 bbox_line( 0, 4 );
 bbox_line( 1, 5 );
 bbox_line( 2, 6 );
 bbox_line( 3, 7 );
 
 #undef bbox_line
}
 
 
MODEL_3D::MODEL_3D( const S3DMODEL& a3DModel, MATERIAL_MODE aMaterialMode )
{
 wxLogTrace( m_logTrace, wxT( "MODEL_3D::MODEL_3D %u meshes %u materials" ),
 static_cast<unsigned int>( a3DModel.m_MeshesSize ),
 static_cast<unsigned int>( a3DModel.m_MaterialsSize ) );
 
 auto start_time = std::chrono::high_resolution_clock::now();
 GLuint buffers[8];
 
 glGenBuffers( 6, buffers );
 m_bbox_vertex_buffer = buffers[2];
 m_bbox_index_buffer = buffers[3];
 m_vertex_buffer = buffers[4];
 m_index_buffer = buffers[5];
 
 // Validate a3DModel pointers
 wxASSERT( a3DModel.m_Materials != nullptr );
 wxASSERT( a3DModel.m_Meshes != nullptr );
 wxASSERT( a3DModel.m_MaterialsSize > 0 );
 wxASSERT( a3DModel.m_MeshesSize > 0 );
 
 m_materialMode = aMaterialMode;
 
 if( a3DModel.m_Materials == nullptr || a3DModel.m_Meshes == nullptr
 || a3DModel.m_MaterialsSize == 0 || a3DModel.m_MeshesSize == 0 )
 return;
 
 // create empty bbox for each mesh. it will be updated when the vertices are copied.
 m_meshes_bbox.resize( a3DModel.m_MeshesSize );
 
 // copy materials for later use during rendering.
 m_materials.reserve( a3DModel.m_MaterialsSize );
 
 for( unsigned int i = 0; i < a3DModel.m_MaterialsSize; ++i )
 m_materials.emplace_back( a3DModel.m_Materials[i] );
 
 // build temporary vertex and index buffers for bounding boxes.
 // the first box is the outer box.
 std::vector<VERTEX> bbox_tmp_vertices( ( m_meshes_bbox.size() + 1 ) * bbox_vtx_count );
 std::vector<GLuint> bbox_tmp_indices( ( m_meshes_bbox.size() + 1 ) * bbox_idx_count );
 
 // group all meshes by material.
 // for each material create a combined vertex and index buffer.
 // some models might have many sub-meshes. so iterate over the
 // input meshes only once.
 struct MESH_GROUP
 {
 std::vector<VERTEX> m_vertices;
 std::vector<GLuint> m_indices;
 };
 
 std::vector<MESH_GROUP> mesh_groups( m_materials.size() );
 
 for( unsigned int mesh_i = 0; mesh_i < a3DModel.m_MeshesSize; ++mesh_i )
 {
 const SMESH& mesh = a3DModel.m_Meshes[mesh_i];
 
 // silently ignore meshes that have invalid material references or invalid geometry.
 if( mesh.m_MaterialIdx >= m_materials.size()
 || mesh.m_Positions == nullptr
 || mesh.m_FaceIdx == nullptr
 || mesh.m_Normals == nullptr
 || mesh.m_FaceIdxSize == 0
 || mesh.m_VertexSize == 0 )
 {
 continue;
 }
 
 MESH_GROUP& mesh_group = mesh_groups[mesh.m_MaterialIdx];
 MATERIAL& material = m_materials[mesh.m_MaterialIdx];
 
 if( material.IsTransparent() && m_materialMode != MATERIAL_MODE::DIFFUSE_ONLY )
 m_have_transparent_meshes = true;
 else
 m_have_opaque_meshes = true;
 
 const unsigned int vtx_offset = mesh_group.m_vertices.size();
 mesh_group.m_vertices.resize( mesh_group.m_vertices.size() + mesh.m_VertexSize );
 
 // copy vertex data and update the bounding box.
 // use material color for mesh bounding box or some sort of average vertex color.
 glm::vec3 avg_color = material.m_Diffuse;
 
 BBOX_3D &mesh_bbox = m_meshes_bbox[mesh_i];
 
 for( unsigned int vtx_i = 0; vtx_i < mesh.m_VertexSize; ++vtx_i )
 {
 mesh_bbox.Union( mesh.m_Positions[vtx_i] );
 
 VERTEX& vtx_out = mesh_group.m_vertices[vtx_offset + vtx_i];
 
 vtx_out.m_pos = mesh.m_Positions[vtx_i];
 vtx_out.m_nrm = glm::clamp( glm::vec4( mesh.m_Normals[vtx_i], 1.0f ) * 127.0f,
 -127.0f, 127.0f );
 
 vtx_out.m_tex_uv = mesh.m_Texcoords != nullptr ? mesh.m_Texcoords[vtx_i]
 : glm::vec2 (0);
 
 if( mesh.m_Color != nullptr )
 {
 avg_color = ( avg_color + mesh.m_Color[vtx_i] ) * 0.5f;
 
 vtx_out.m_color =
 glm::clamp( glm::vec4( mesh.m_Color[vtx_i],
 1 - material.m_Transparency ) * 255.0f,
 0.0f, 255.0f );
 
 vtx_out.m_cad_color =
 glm::clamp( glm::vec4( MaterialDiffuseToColorCAD( mesh.m_Color[vtx_i] ),
 1 ) * 255.0f, 0.0f, 255.0f );
 }
 else
 {
 // the mesh will be rendered with other meshes that might have
 // vertex colors. thus, we can't enable/disable vertex colors
 // for individual meshes during rendering.
 
 // if there are no vertex colors, use material color instead.
 vtx_out.m_color =
 glm::clamp( glm::vec4( material.m_Diffuse,
 1 - material.m_Transparency ) * 255.0f,
 0.0f, 255.0f );
 
 vtx_out.m_cad_color =
 glm::clamp( glm::vec4 ( MaterialDiffuseToColorCAD( material.m_Diffuse ),
 1 ) * 255.0f,
 0.0f, 255.0f );
 }
 }
 
 if( mesh_bbox.IsInitialized() )
 {
 // generate geometry for the bounding box
 MakeBbox( mesh_bbox, ( mesh_i + 1 ) * bbox_vtx_count,
 &bbox_tmp_vertices[( mesh_i + 1 ) * bbox_vtx_count],
 &bbox_tmp_indices[( mesh_i + 1 ) * bbox_idx_count],
 { avg_color, 1.0f } );
 
 // bump the outer bounding box
 m_model_bbox.Union( mesh_bbox );
 
 // add to the material group
 material.m_bbox.Union( mesh_bbox );
 }
 
 
 // append indices of this mesh to the mesh group.
 const unsigned int idx_offset = mesh_group.m_indices.size();
 unsigned int use_idx_count = mesh.m_FaceIdxSize;
 
 if( use_idx_count % 3 != 0 )
 {
 wxLogTrace( m_logTrace, wxT( " index count %u not multiple of 3, truncating" ),
 static_cast<unsigned int>( use_idx_count ) );
 use_idx_count = ( use_idx_count / 3 ) * 3;
 }
 
 mesh_group.m_indices.resize( mesh_group.m_indices.size() + use_idx_count );
 
 for( unsigned int idx_i = 0; idx_i < use_idx_count; ++idx_i )
 {
 if( mesh.m_FaceIdx[idx_i] >= mesh.m_VertexSize )
 {
 wxLogTrace( m_logTrace, wxT( " index %u out of range (%u)" ),
 static_cast<unsigned int>( mesh.m_FaceIdx[idx_i] ),
 static_cast<unsigned int>( mesh.m_VertexSize ) );
 
 // FIXME: should skip this triangle
 }
 
 mesh_group.m_indices[idx_offset + idx_i] = mesh.m_FaceIdx[idx_i] + vtx_offset;
 }
 }
 
 // generate geometry for the outer bounding box
 if( m_model_bbox.IsInitialized() )
 MakeBbox( m_model_bbox, 0, &bbox_tmp_vertices[0], &bbox_tmp_indices[0],
 { 0.0f, 1.0f, 0.0f, 1.0f } );
 
 // create bounding box buffers
 glGenBuffers( 1, &m_bbox_vertex_buffer );
 glBindBuffer( GL_ARRAY_BUFFER, m_bbox_vertex_buffer );
 glBufferData( GL_ARRAY_BUFFER, sizeof( VERTEX ) * bbox_tmp_vertices.size(),
 bbox_tmp_vertices.data(), GL_STATIC_DRAW );
 
 glBindBuffer( GL_ELEMENT_ARRAY_BUFFER, m_bbox_index_buffer );
 
 if( bbox_tmp_vertices.size() <= std::numeric_limits<GLushort>::max() )
 {
 m_bbox_index_buffer_type = GL_UNSIGNED_SHORT;
 
 auto u16buf = std::make_unique<GLushort[]>( bbox_tmp_indices.size() );
 
 for( unsigned int i = 0; i < bbox_tmp_indices.size(); ++i )
 u16buf[i] = static_cast<GLushort>( bbox_tmp_indices[i] );
 
 glBufferData( GL_ELEMENT_ARRAY_BUFFER, sizeof( GLushort ) * bbox_tmp_indices.size(),
 u16buf.get(), GL_STATIC_DRAW );
 }
 else
 {
 m_bbox_index_buffer_type = GL_UNSIGNED_INT;
 glBufferData( GL_ELEMENT_ARRAY_BUFFER, sizeof( GLuint ) * bbox_tmp_indices.size(),
 bbox_tmp_indices.data(), GL_STATIC_DRAW );
 }
 
 // merge the mesh group geometry data.
 unsigned int total_vertex_count = 0;
 unsigned int total_index_count = 0;
 
 for( const MESH_GROUP& mg : mesh_groups )
 {
 total_vertex_count += mg.m_vertices.size();
 total_index_count += mg.m_indices.size();
 }
 
 wxLogTrace( m_logTrace, wxT( " total %u vertices, %u indices" ),
 total_vertex_count, total_index_count );
 
 glBindBuffer( GL_ARRAY_BUFFER, m_vertex_buffer );
 glBufferData( GL_ARRAY_BUFFER, sizeof( VERTEX ) * total_vertex_count,
 nullptr, GL_STATIC_DRAW );
 
 unsigned int idx_size = 0;
 
 if( total_vertex_count <= std::numeric_limits<GLushort>::max() )
 {
 m_index_buffer_type = GL_UNSIGNED_SHORT;
 idx_size = sizeof( GLushort );
 }
 else
 {
 m_index_buffer_type = GL_UNSIGNED_INT;
 idx_size = sizeof( GLuint );
 }
 
 // temporary index buffer which will contain either GLushort or GLuint
 // type indices. allocate with a bit of meadow at the end.
 auto tmp_idx = std::make_unique<GLuint[]>( ( idx_size * total_index_count + 8 ) / sizeof( GLuint ) );
 
 unsigned int prev_vtx_count = 0;
 unsigned int idx_offset = 0;
 unsigned int vtx_offset = 0;
 
 for( unsigned int mg_i = 0; mg_i < mesh_groups.size (); ++mg_i )
 {
 MESH_GROUP& mg = mesh_groups[mg_i];
 MATERIAL& mat = m_materials[mg_i];
 uintptr_t tmp_idx_ptr = reinterpret_cast<uintptr_t>( tmp_idx.get() );
 
 if( m_index_buffer_type == GL_UNSIGNED_SHORT )
 {
 GLushort* idx_out = reinterpret_cast<GLushort*>( tmp_idx_ptr + idx_offset );
 
 for( GLuint idx : mg.m_indices )
 *idx_out++ = static_cast<GLushort>( idx + prev_vtx_count );
 }
 else if( m_index_buffer_type == GL_UNSIGNED_INT )
 {
 GLuint* idx_out = reinterpret_cast<GLuint*>( tmp_idx_ptr + idx_offset );
 
 for( GLuint idx : mg.m_indices )
 *idx_out++ = static_cast<GLuint>( idx + prev_vtx_count );
 }
 
 glBufferSubData( GL_ARRAY_BUFFER, vtx_offset, mg.m_vertices.size() * sizeof( VERTEX ),
 mg.m_vertices.data() );
 
 mat.m_render_idx_buffer_offset = idx_offset;
 mat.m_render_idx_count = mg.m_indices.size();
 
 prev_vtx_count += mg.m_vertices.size();
 idx_offset += mg.m_indices.size() * idx_size;
 vtx_offset += mg.m_vertices.size() * sizeof( VERTEX );
 }
 
 glBindBuffer( GL_ELEMENT_ARRAY_BUFFER, m_index_buffer );
 glBufferData( GL_ELEMENT_ARRAY_BUFFER, idx_size * total_index_count, tmp_idx.get(),
 GL_STATIC_DRAW );
 
 glBindBuffer( GL_ARRAY_BUFFER, 0 );
 glBindBuffer( GL_ELEMENT_ARRAY_BUFFER, 0 );
 
 auto end_time = std::chrono::high_resolution_clock::now();
 
 wxLogTrace( m_logTrace, wxT( " loaded in %u ms\n" ),
 (unsigned int)std::chrono::duration_cast<std::chrono::milliseconds> (
 end_time - start_time).count() );
}
 
 
void MODEL_3D::BeginDrawMulti( bool aUseColorInformation )
{
 glEnableClientState( GL_VERTEX_ARRAY );
 glEnableClientState( GL_NORMAL_ARRAY );
 
 if( aUseColorInformation )
 {
 glEnableClientState( GL_COLOR_ARRAY );
 glEnableClientState( GL_TEXTURE_COORD_ARRAY );
 glEnable( GL_COLOR_MATERIAL );
 }
 
 glColorMaterial( GL_FRONT_AND_BACK, GL_AMBIENT_AND_DIFFUSE );
}
 
 
void MODEL_3D::EndDrawMulti()
{
 glDisable( GL_COLOR_MATERIAL );
 glDisableClientState( GL_VERTEX_ARRAY );
 glDisableClientState( GL_NORMAL_ARRAY );
 glDisableClientState( GL_COLOR_ARRAY );
 glDisableClientState( GL_TEXTURE_COORD_ARRAY );
 
 glBindBuffer( GL_ARRAY_BUFFER, 0 );
 glBindBuffer( GL_ELEMENT_ARRAY_BUFFER, 0 );
}
 
 
void MODEL_3D::Draw( bool aTransparent, float aOpacity, bool aUseSelectedMaterial,
 const SFVEC3F& aSelectionColor,
 const glm::mat4 *aModelWorldMatrix,
 const SFVEC3F *aCameraWorldPos ) const
{
 if( aOpacity <= FLT_EPSILON )
 return;
 
 if( !glBindBuffer )
 throw std::runtime_error( "The OpenGL context no longer exists: unable to draw" );
 
 glBindBuffer( GL_ARRAY_BUFFER, m_vertex_buffer );
 glBindBuffer( GL_ELEMENT_ARRAY_BUFFER, m_index_buffer );
 
 glVertexPointer( 3, GL_FLOAT, sizeof( VERTEX ),
 reinterpret_cast<const void*>( offsetof( VERTEX, m_pos ) ) );
 
 glNormalPointer( GL_BYTE, sizeof( VERTEX ),
 reinterpret_cast<const void*>( offsetof( VERTEX, m_nrm ) ) );
 
 glColorPointer( 4, GL_UNSIGNED_BYTE, sizeof( VERTEX ),
 reinterpret_cast<const void*>( m_materialMode == MATERIAL_MODE::CAD_MODE
 ? offsetof( VERTEX, m_cad_color )
 : offsetof( VERTEX, m_color ) ) );
 
 glTexCoordPointer( 2, GL_FLOAT, sizeof( VERTEX ),
 reinterpret_cast<const void*>( offsetof( VERTEX, m_tex_uv ) ) );
 
 const SFVEC4F param = SFVEC4F( 1.0f, 1.0f, 1.0f, aOpacity );
 
 glTexEnvfv( GL_TEXTURE_ENV, GL_TEXTURE_ENV_COLOR, (const float*)&param.x );
 
 std::vector<const MODEL_3D::MATERIAL *> materialsToRender;
 
 materialsToRender.reserve( m_materials.size() );
 
 if( aModelWorldMatrix && aCameraWorldPos )
 {
 // Sort Material groups
 
 std::vector<std::pair<const MODEL_3D::MATERIAL*, float>> materialsSorted;
 
 // Calculate the distance to the camera for each material group
 for( const MODEL_3D::MATERIAL& mat : m_materials )
 {
 if( mat.m_render_idx_count == 0 )
 {
 continue;
 }
 
 if( ( mat.IsTransparent() != aTransparent )
 && ( aOpacity >= 1.0f )
 && m_materialMode != MATERIAL_MODE::DIFFUSE_ONLY )
 {
 continue;
 }
 
 const BBOX_3D& bBox = mat.m_bbox;
 const SFVEC3F& bBoxCenter = bBox.GetCenter();
 const SFVEC3F bBoxWorld = *aModelWorldMatrix * glm::vec4( bBoxCenter, 1.0f );
 
 const float distanceToCamera = glm::length( *aCameraWorldPos - bBoxWorld );
 
 materialsSorted.emplace_back( &mat, distanceToCamera );
 }
 
 // Sort from back to front
 std::sort( materialsSorted.begin(), materialsSorted.end(),
 [&]( std::pair<const MODEL_3D::MATERIAL*, float>& a,
 std::pair<const MODEL_3D::MATERIAL*, float>& b ) {
 // If A is inside B, then A is rendered first
 if( b.first->m_bbox.Inside( a.first->m_bbox ) )
 {
 return true;
 }
 else
 {
 if( a.first->m_bbox.Inside( b.first->m_bbox ) )
 {
 return false;
 }
 }
 
 return a.second > b.second;
 } );
 
 for( const std::pair<const MODEL_3D::MATERIAL*, float>& mat : materialsSorted )
 {
 materialsToRender.push_back( mat.first );
 }
 }
 else
 {
 for( const MODEL_3D::MATERIAL& mat : m_materials )
 {
 // There is at least one default material created in case a mesh has no declared materials.
 // Most meshes have a material, so usually the first material will have nothing to render and is skip.
 // See S3D::GetModel for more details.
 if( mat.m_render_idx_count == 0 )
 {
 continue;
 }
 
 if( ( mat.IsTransparent() != aTransparent )
 && ( aOpacity >= 1.0f )
 && m_materialMode != MATERIAL_MODE::DIFFUSE_ONLY )
 {
 continue;
 }
 
 materialsToRender.push_back( &mat );
 }
 }
 
 for( const MODEL_3D::MATERIAL* mat : materialsToRender )
 {
 switch( m_materialMode )
 {
 case MATERIAL_MODE::NORMAL:
 OglSetMaterial( *mat, aOpacity, aUseSelectedMaterial, aSelectionColor );
 break;
 
 case MATERIAL_MODE::DIFFUSE_ONLY:
 OglSetDiffuseMaterial( mat->m_Diffuse, aOpacity, aUseSelectedMaterial, aSelectionColor );
 break;
 
 case MATERIAL_MODE::CAD_MODE:
 OglSetDiffuseMaterial( MaterialDiffuseToColorCAD( mat->m_Diffuse ), aOpacity,
 aUseSelectedMaterial, aSelectionColor );
 break;
 
 default:
 break;
 }
 
 glDrawElements( GL_TRIANGLES, mat->m_render_idx_count, m_index_buffer_type,
 reinterpret_cast<const void*>(
 static_cast<uintptr_t>( mat->m_render_idx_buffer_offset ) ) );
 }
}
 
 
MODEL_3D::~MODEL_3D()
{
 if( glDeleteBuffers )
 {
 glDeleteBuffers( 1, &m_vertex_buffer );
 glDeleteBuffers( 1, &m_index_buffer );
 glDeleteBuffers( 1, &m_bbox_vertex_buffer );
 glDeleteBuffers( 1, &m_bbox_index_buffer );
 }
}
 
 
void MODEL_3D::DrawBbox() const
{
 if( !glBindBuffer )
 throw std::runtime_error( "The OpenGL context no longer exists: unable to draw bbox" );
 
 glBindBuffer( GL_ARRAY_BUFFER, m_bbox_vertex_buffer );
 glBindBuffer( GL_ELEMENT_ARRAY_BUFFER, m_bbox_index_buffer );
 
 glVertexPointer( 3, GL_FLOAT, sizeof( VERTEX ),
 reinterpret_cast<const void*>( offsetof( VERTEX, m_pos ) ) );
 
 glColorPointer( 4, GL_UNSIGNED_BYTE, sizeof( VERTEX ),
 reinterpret_cast<const void*>( offsetof( VERTEX, m_color ) ) );
 
 glDrawElements( GL_LINES, bbox_idx_count, m_bbox_index_buffer_type,
 reinterpret_cast<const void*>( 0 ) );
}
 
 
void MODEL_3D::DrawBboxes() const
{
 if( !glBindBuffer )
 throw std::runtime_error( "The OpenGL context no longer exists: unable to draw bboxes" );
 
 glBindBuffer( GL_ARRAY_BUFFER, m_bbox_vertex_buffer );
 glBindBuffer( GL_ELEMENT_ARRAY_BUFFER, m_bbox_index_buffer );
 
 glVertexPointer( 3, GL_FLOAT, sizeof( VERTEX ),
 reinterpret_cast<const void*>( offsetof( VERTEX, m_pos ) ) );
 
 glColorPointer( 4, GL_UNSIGNED_BYTE, sizeof( VERTEX ),
 reinterpret_cast<const void*>( offsetof( VERTEX, m_color ) ) );
 
 unsigned int idx_size = m_bbox_index_buffer_type == GL_UNSIGNED_SHORT ? sizeof( GLushort )
 : sizeof( GLuint );
 
 glDrawElements( GL_LINES, bbox_idx_count * m_meshes_bbox.size(), m_bbox_index_buffer_type,
 reinterpret_cast<const void*>(
 static_cast<uintptr_t>( bbox_idx_count * idx_size ) ) );
}