Quake 1 (idtech2) model format (MDL version 6): GraphViz block diagram (.dot) source

Quake 1 model format is used to store 3D models completely with textures and animations used in the game. Quake 1 engine (retroactively named "idtech2") is a popular 3D engine first used for Quake game by id Software in 1996.

Model is constructed traditionally from vertices in 3D space, faces which connect vertices, textures ("skins", i.e. 2D bitmaps) and texture UV mapping information. As opposed to more modern, bones-based animation formats, Quake model was animated by changing locations of all vertices it included in 3D space, frame by frame.

File format stores:

"Skins" — effectively 2D bitmaps which will be used as a texture. Every model can have multiple skins — e.g. these can be switched to depict various levels of damage to the monsters. Bitmaps are 8-bit-per-pixel, indexed in global Quake palette, subject to lighting and gamma adjustment when rendering in the game using colormap technique.
"Texture coordinates" — UV coordinates, mapping 3D vertices to skin coordinates.
"Triangles" — triangular faces connecting 3D vertices.
"Frames" — locations of vertices in 3D space; can include more than one frame, thus allowing representation of different frames for animation purposes.

Originally, 3D geometry for models for Quake was designed in Alias PowerAnimator, precursor of modern day Autodesk Maya and Autodesk Alias. Therefore, 3D-related part of Quake model format followed closely Alias TRI format, and Quake development utilities included a converter from Alias TRI (modelgen).

Skins (textures) where prepared as LBM bitmaps with the help from texmap utility in the same development utilities toolkit.

Application

Quake 1 (idtech2)

File extension

mdl

KS implementation details

License: CC0-1.0

Minimal Kaitai Struct required: 0.1

This page hosts a formal specification of Quake 1 (idtech2) model format (MDL version 6) using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.

GraphViz block diagram source

quake_mdl.dot

Download

digraph {
	rankdir=LR;
	node [shape=plaintext];
	subgraph cluster__quake_mdl {
		label="QuakeMdl";
		graph[style=dotted];

		quake_mdl__seq [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
			<TR><TD BGCOLOR="#E0FFE0">pos</TD><TD BGCOLOR="#E0FFE0">size</TD><TD BGCOLOR="#E0FFE0">type</TD><TD BGCOLOR="#E0FFE0">id</TD></TR>
			<TR><TD PORT="header_pos">0</TD><TD PORT="header_size">84</TD><TD>MdlHeader</TD><TD PORT="header_type">header</TD></TR>
			<TR><TD PORT="skins_pos">84</TD><TD PORT="skins_size">...</TD><TD>MdlSkin</TD><TD PORT="skins_type">skins</TD></TR>
			<TR><TD COLSPAN="4" PORT="skins__repeat">repeat header.num_skins times</TD></TR>
			<TR><TD PORT="texture_coordinates_pos">...</TD><TD PORT="texture_coordinates_size">12</TD><TD>MdlTexcoord</TD><TD PORT="texture_coordinates_type">texture_coordinates</TD></TR>
			<TR><TD COLSPAN="4" PORT="texture_coordinates__repeat">repeat header.num_verts times</TD></TR>
			<TR><TD PORT="triangles_pos">...</TD><TD PORT="triangles_size">16</TD><TD>MdlTriangle</TD><TD PORT="triangles_type">triangles</TD></TR>
			<TR><TD COLSPAN="4" PORT="triangles__repeat">repeat header.num_tris times</TD></TR>
			<TR><TD PORT="frames_pos">...</TD><TD PORT="frames_size">...</TD><TD>MdlFrame</TD><TD PORT="frames_type">frames</TD></TR>
			<TR><TD COLSPAN="4" PORT="frames__repeat">repeat header.num_frames times</TD></TR>
		</TABLE>>];
		subgraph cluster__mdl_vertex {
			label="QuakeMdl::MdlVertex";
			graph[style=dotted];

			mdl_vertex__seq [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
				<TR><TD BGCOLOR="#E0FFE0">pos</TD><TD BGCOLOR="#E0FFE0">size</TD><TD BGCOLOR="#E0FFE0">type</TD><TD BGCOLOR="#E0FFE0">id</TD></TR>
				<TR><TD PORT="values_pos">0</TD><TD PORT="values_size">1</TD><TD>u1</TD><TD PORT="values_type">values</TD></TR>
				<TR><TD COLSPAN="4" PORT="values__repeat">repeat 3 times</TD></TR>
				<TR><TD PORT="normal_index_pos">3</TD><TD PORT="normal_index_size">1</TD><TD>u1</TD><TD PORT="normal_index_type">normal_index</TD></TR>
			</TABLE>>];
		}
		subgraph cluster__mdl_texcoord {
			label="QuakeMdl::MdlTexcoord";
			graph[style=dotted];

			mdl_texcoord__seq [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
				<TR><TD BGCOLOR="#E0FFE0">pos</TD><TD BGCOLOR="#E0FFE0">size</TD><TD BGCOLOR="#E0FFE0">type</TD><TD BGCOLOR="#E0FFE0">id</TD></TR>
				<TR><TD PORT="on_seam_pos">0</TD><TD PORT="on_seam_size">4</TD><TD>s4le</TD><TD PORT="on_seam_type">on_seam</TD></TR>
				<TR><TD PORT="s_pos">4</TD><TD PORT="s_size">4</TD><TD>s4le</TD><TD PORT="s_type">s</TD></TR>
				<TR><TD PORT="t_pos">8</TD><TD PORT="t_size">4</TD><TD>s4le</TD><TD PORT="t_type">t</TD></TR>
			</TABLE>>];
		}
		subgraph cluster__mdl_header {
			label="QuakeMdl::MdlHeader";
			graph[style=dotted];

			mdl_header__seq [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
				<TR><TD BGCOLOR="#E0FFE0">pos</TD><TD BGCOLOR="#E0FFE0">size</TD><TD BGCOLOR="#E0FFE0">type</TD><TD BGCOLOR="#E0FFE0">id</TD></TR>
				<TR><TD PORT="ident_pos">0</TD><TD PORT="ident_size">4</TD><TD></TD><TD PORT="ident_type">ident</TD></TR>
				<TR><TD PORT="version_pos">4</TD><TD PORT="version_size">4</TD><TD>s4le</TD><TD PORT="version_type">version</TD></TR>
				<TR><TD PORT="scale_pos">8</TD><TD PORT="scale_size">12</TD><TD>Vec3</TD><TD PORT="scale_type">scale</TD></TR>
				<TR><TD PORT="origin_pos">20</TD><TD PORT="origin_size">12</TD><TD>Vec3</TD><TD PORT="origin_type">origin</TD></TR>
				<TR><TD PORT="radius_pos">32</TD><TD PORT="radius_size">4</TD><TD>f4le</TD><TD PORT="radius_type">radius</TD></TR>
				<TR><TD PORT="eye_position_pos">36</TD><TD PORT="eye_position_size">12</TD><TD>Vec3</TD><TD PORT="eye_position_type">eye_position</TD></TR>
				<TR><TD PORT="num_skins_pos">48</TD><TD PORT="num_skins_size">4</TD><TD>s4le</TD><TD PORT="num_skins_type">num_skins</TD></TR>
				<TR><TD PORT="skin_width_pos">52</TD><TD PORT="skin_width_size">4</TD><TD>s4le</TD><TD PORT="skin_width_type">skin_width</TD></TR>
				<TR><TD PORT="skin_height_pos">56</TD><TD PORT="skin_height_size">4</TD><TD>s4le</TD><TD PORT="skin_height_type">skin_height</TD></TR>
				<TR><TD PORT="num_verts_pos">60</TD><TD PORT="num_verts_size">4</TD><TD>s4le</TD><TD PORT="num_verts_type">num_verts</TD></TR>
				<TR><TD PORT="num_tris_pos">64</TD><TD PORT="num_tris_size">4</TD><TD>s4le</TD><TD PORT="num_tris_type">num_tris</TD></TR>
				<TR><TD PORT="num_frames_pos">68</TD><TD PORT="num_frames_size">4</TD><TD>s4le</TD><TD PORT="num_frames_type">num_frames</TD></TR>
				<TR><TD PORT="synctype_pos">72</TD><TD PORT="synctype_size">4</TD><TD>s4le</TD><TD PORT="synctype_type">synctype</TD></TR>
				<TR><TD PORT="flags_pos">76</TD><TD PORT="flags_size">4</TD><TD>s4le</TD><TD PORT="flags_type">flags</TD></TR>
				<TR><TD PORT="size_pos">80</TD><TD PORT="size_size">4</TD><TD>f4le</TD><TD PORT="size_type">size</TD></TR>
			</TABLE>>];
			mdl_header__inst__skin_size [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
				<TR><TD BGCOLOR="#E0FFE0">id</TD><TD BGCOLOR="#E0FFE0">value</TD></TR>
				<TR><TD>skin_size</TD><TD>(skin_width * skin_height)</TD></TR>
			</TABLE>>];
		}
		subgraph cluster__mdl_skin {
			label="QuakeMdl::MdlSkin";
			graph[style=dotted];

			mdl_skin__seq [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
				<TR><TD BGCOLOR="#E0FFE0">pos</TD><TD BGCOLOR="#E0FFE0">size</TD><TD BGCOLOR="#E0FFE0">type</TD><TD BGCOLOR="#E0FFE0">id</TD></TR>
				<TR><TD PORT="group_pos">0</TD><TD PORT="group_size">4</TD><TD>s4le</TD><TD PORT="group_type">group</TD></TR>
				<TR><TD PORT="single_texture_data_pos">4</TD><TD PORT="single_texture_data_size">_root.header.skin_size</TD><TD></TD><TD PORT="single_texture_data_type">single_texture_data</TD></TR>
				<TR><TD PORT="num_frames_pos">...</TD><TD PORT="num_frames_size">4</TD><TD>u4le</TD><TD PORT="num_frames_type">num_frames</TD></TR>
				<TR><TD PORT="frame_times_pos">...</TD><TD PORT="frame_times_size">4</TD><TD>f4le</TD><TD PORT="frame_times_type">frame_times</TD></TR>
				<TR><TD COLSPAN="4" PORT="frame_times__repeat">repeat num_frames times</TD></TR>
				<TR><TD PORT="group_texture_data_pos">...</TD><TD PORT="group_texture_data_size">_root.header.skin_size</TD><TD></TD><TD PORT="group_texture_data_type">group_texture_data</TD></TR>
				<TR><TD COLSPAN="4" PORT="group_texture_data__repeat">repeat num_frames times</TD></TR>
			</TABLE>>];
		}
		subgraph cluster__mdl_frame {
			label="QuakeMdl::MdlFrame";
			graph[style=dotted];

			mdl_frame__seq [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
				<TR><TD BGCOLOR="#E0FFE0">pos</TD><TD BGCOLOR="#E0FFE0">size</TD><TD BGCOLOR="#E0FFE0">type</TD><TD BGCOLOR="#E0FFE0">id</TD></TR>
				<TR><TD PORT="type_pos">0</TD><TD PORT="type_size">4</TD><TD>s4le</TD><TD PORT="type_type">type</TD></TR>
				<TR><TD PORT="min_pos">4</TD><TD PORT="min_size">4</TD><TD>MdlVertex</TD><TD PORT="min_type">min</TD></TR>
				<TR><TD PORT="max_pos">8</TD><TD PORT="max_size">4</TD><TD>MdlVertex</TD><TD PORT="max_type">max</TD></TR>
				<TR><TD PORT="time_pos">12</TD><TD PORT="time_size">4</TD><TD>f4le</TD><TD PORT="time_type">time</TD></TR>
				<TR><TD COLSPAN="4" PORT="time__repeat">repeat type times</TD></TR>
				<TR><TD PORT="frames_pos">...</TD><TD PORT="frames_size">...</TD><TD>MdlSimpleFrame</TD><TD PORT="frames_type">frames</TD></TR>
				<TR><TD COLSPAN="4" PORT="frames__repeat">repeat num_simple_frames times</TD></TR>
			</TABLE>>];
			mdl_frame__inst__num_simple_frames [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
				<TR><TD BGCOLOR="#E0FFE0">id</TD><TD BGCOLOR="#E0FFE0">value</TD></TR>
				<TR><TD>num_simple_frames</TD><TD>(type == 0 ? 1 : type)</TD></TR>
			</TABLE>>];
		}
		subgraph cluster__mdl_simple_frame {
			label="QuakeMdl::MdlSimpleFrame";
			graph[style=dotted];

			mdl_simple_frame__seq [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
				<TR><TD BGCOLOR="#E0FFE0">pos</TD><TD BGCOLOR="#E0FFE0">size</TD><TD BGCOLOR="#E0FFE0">type</TD><TD BGCOLOR="#E0FFE0">id</TD></TR>
				<TR><TD PORT="bbox_min_pos">0</TD><TD PORT="bbox_min_size">4</TD><TD>MdlVertex</TD><TD PORT="bbox_min_type">bbox_min</TD></TR>
				<TR><TD PORT="bbox_max_pos">4</TD><TD PORT="bbox_max_size">4</TD><TD>MdlVertex</TD><TD PORT="bbox_max_type">bbox_max</TD></TR>
				<TR><TD PORT="name_pos">8</TD><TD PORT="name_size">16</TD><TD>str(ASCII)</TD><TD PORT="name_type">name</TD></TR>
				<TR><TD PORT="vertices_pos">24</TD><TD PORT="vertices_size">4</TD><TD>MdlVertex</TD><TD PORT="vertices_type">vertices</TD></TR>
				<TR><TD COLSPAN="4" PORT="vertices__repeat">repeat _root.header.num_verts times</TD></TR>
			</TABLE>>];
		}
		subgraph cluster__mdl_triangle {
			label="QuakeMdl::MdlTriangle";
			graph[style=dotted];

			mdl_triangle__seq [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
				<TR><TD BGCOLOR="#E0FFE0">pos</TD><TD BGCOLOR="#E0FFE0">size</TD><TD BGCOLOR="#E0FFE0">type</TD><TD BGCOLOR="#E0FFE0">id</TD></TR>
				<TR><TD PORT="faces_front_pos">0</TD><TD PORT="faces_front_size">4</TD><TD>s4le</TD><TD PORT="faces_front_type">faces_front</TD></TR>
				<TR><TD PORT="vertices_pos">4</TD><TD PORT="vertices_size">4</TD><TD>s4le</TD><TD PORT="vertices_type">vertices</TD></TR>
				<TR><TD COLSPAN="4" PORT="vertices__repeat">repeat 3 times</TD></TR>
			</TABLE>>];
		}
		subgraph cluster__vec3 {
			label="QuakeMdl::Vec3";
			graph[style=dotted];

			vec3__seq [label=<<TABLE BORDER="0" CELLBORDER="1" CELLSPACING="0">
				<TR><TD BGCOLOR="#E0FFE0">pos</TD><TD BGCOLOR="#E0FFE0">size</TD><TD BGCOLOR="#E0FFE0">type</TD><TD BGCOLOR="#E0FFE0">id</TD></TR>
				<TR><TD PORT="x_pos">0</TD><TD PORT="x_size">4</TD><TD>f4le</TD><TD PORT="x_type">x</TD></TR>
				<TR><TD PORT="y_pos">4</TD><TD PORT="y_size">4</TD><TD>f4le</TD><TD PORT="y_type">y</TD></TR>
				<TR><TD PORT="z_pos">8</TD><TD PORT="z_size">4</TD><TD>f4le</TD><TD PORT="z_type">z</TD></TR>
			</TABLE>>];
		}
	}
	quake_mdl__seq:header_type -> mdl_header__seq [style=bold];
	quake_mdl__seq:skins_type -> mdl_skin__seq [style=bold];
	mdl_header__seq:num_skins_type -> quake_mdl__seq:skins__repeat [color="#404040"];
	quake_mdl__seq:texture_coordinates_type -> mdl_texcoord__seq [style=bold];
	mdl_header__seq:num_verts_type -> quake_mdl__seq:texture_coordinates__repeat [color="#404040"];
	quake_mdl__seq:triangles_type -> mdl_triangle__seq [style=bold];
	mdl_header__seq:num_tris_type -> quake_mdl__seq:triangles__repeat [color="#404040"];
	quake_mdl__seq:frames_type -> mdl_frame__seq [style=bold];
	mdl_header__seq:num_frames_type -> quake_mdl__seq:frames__repeat [color="#404040"];
	mdl_header__seq:scale_type -> vec3__seq [style=bold];
	mdl_header__seq:origin_type -> vec3__seq [style=bold];
	mdl_header__seq:eye_position_type -> vec3__seq [style=bold];
	mdl_header__seq:skin_width_type -> mdl_header__inst__skin_size [color="#404040"];
	mdl_header__seq:skin_height_type -> mdl_header__inst__skin_size [color="#404040"];
	mdl_header__inst__skin_size:skin_size_type -> mdl_skin__seq:single_texture_data_size [color="#404040"];
	mdl_skin__seq:num_frames_type -> mdl_skin__seq:frame_times__repeat [color="#404040"];
	mdl_header__inst__skin_size:skin_size_type -> mdl_skin__seq:group_texture_data_size [color="#404040"];
	mdl_skin__seq:num_frames_type -> mdl_skin__seq:group_texture_data__repeat [color="#404040"];
	mdl_frame__seq:min_type -> mdl_vertex__seq [style=bold];
	mdl_frame__seq:max_type -> mdl_vertex__seq [style=bold];
	mdl_frame__seq:type_type -> mdl_frame__seq:time__repeat [color="#404040"];
	mdl_frame__seq:frames_type -> mdl_simple_frame__seq [style=bold];
	mdl_frame__inst__num_simple_frames:num_simple_frames_type -> mdl_frame__seq:frames__repeat [color="#404040"];
	mdl_frame__seq:type_type -> mdl_frame__inst__num_simple_frames [color="#404040"];
	mdl_frame__seq:type_type -> mdl_frame__inst__num_simple_frames [color="#404040"];
	mdl_simple_frame__seq:bbox_min_type -> mdl_vertex__seq [style=bold];
	mdl_simple_frame__seq:bbox_max_type -> mdl_vertex__seq [style=bold];
	mdl_simple_frame__seq:vertices_type -> mdl_vertex__seq [style=bold];
	mdl_header__seq:num_verts_type -> mdl_simple_frame__seq:vertices__repeat [color="#404040"];
}