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Descent Level and Mission Format 0.20 <-- Note the version number! ------- ----- --- ------- ------ ---- Legal Notice ----- ------ All material in this document, and the attached source code, is copyright Parallax Software, 1995. It is released solely for the purpose of enabling legitimate owners of the registered version of Descent to create levels and missions to be used with Descent. The release of this information should in no way be construed as implying that copyrights, patents, trademarks or trade secrets of Descent, owned by Parallax or Interplay, are weakened or invalidated. Description ----------- This document describes the level and mission format for the registered version of Descent. It is hoped that this information will help people create their own levels and missions for use with Descent. This document is not complete without the attached source code. The source code is available at: wuarchive.wustl.edu pub/MSDOS_UPLOADS/descent/lvlinfo.zip Notes About Version 0.20 ----- ----- ------- ---- This document, as you might guess from the version number, is not considered complete. It is released under the assumption that it's marginally better than nothing. It will still be difficult for anyone to create an editor to create Descent levels. It will be very difficult to create levels that contain all the features of a complete Descent level, such as keyed doors, locked doors, a control center which triggers doors, robots containing objects, materialization centers, etc. However, it will be a lot easier with this document than without it. This document, and the attached source code, should be enough to enable people to create anarchy levels and missions without unbearable difficulty. There is much information about objects which is not explained. This will be released in a future update. If you're real curious now, a good way to figure out this information is to disassemble an existing "rdl" file. Improved versions of this document will be posted here on an irregular basis. I hope a significantly better version will be posted within a couple weeks. If you find errors in this document, and you will probably find many if you try to use it, please post them in alt.games.descent. Put some identifying information in the Subject, such as "Level Info Error: Hog File Format Bogus" or whatever. Please read the section "About the Included Source Code". This document should not be considered anywhere near complete without constant reference to the source code, particularly the header files. Good luck! All of us at Parallax are looking forward to seeing new levels! -- Mike Kulas, March 17, 1995 Revised June 21, 1995 Plea for Peace ---- --- ----- Please do not contact Parallax or Interplay with questions regarding information in this document. We do not have the resources to answer questions pertaining to level design. We have several people who read alt.games.descent and comp.sys.ibm.pc.games.action every day. If you have questions, please post in these newsgroups and we will answer them as best we can. About the Included Source Code ----- --- -------- ------ ---- The source code included with this document is provided as a document of the level format. Although it started as actual source code from Descent, it is no longer compilable, and much has been removed from the provided functions, including some comments. However, the portions which pertain to loading level data are most likely accurate and complete. In cases in which this document contradicts the source code, the source code should be considered complete. The header files contain data structure definitions. Some of them describe the internal representation of a level, which is very different from the format stored in an "rdl" file. They are provided as a reference to help understand the source code which reads an "rdl" file. Related source code and this document available at: wuarchive.wustl.edu pub/MSDOS_UPLOADS/descent/lvlinfo.zip Overview of Level-Related Files -------- -- ------------- ----- A Descent level is wholly contained in one file. These files have the extension "rdl" for Registered Descent Level. The "rdl" files which are part of Regsitered Descent are all included in the file "descent.hog". There are, by default, no "rdl" files present in the Descent directory. However, if there _were_ an "rdl" file, and it were specified in the "msn" file, it would get loaded, taking precedence over the version of the level in the "hog" file. So, if you wanted to create a new level 1, you would name it "level01.rdl" and place it in the Descent directory. It would get loaded in favor of the level01.rdl in the hog file. Format of RDL File ------ -- --- ---- [Before proceeding with writing an editor, I would strongly encourage anyone to write a level ("rdl" file) disassembler. That should demonstrate whether the information in this document is correct, in addition to providing necessary expertise. Before disassembling level files, you will need to disassemble the "hog" file. That will be the easiest part. See the section "Format of the Hog File".] The function load_level(), which is included in the partial source code, reads a level file from disk. load_level calls load_mine_data_compiled and load_game_data. load_mine_data_compiled loads mine (level structure) data. load_game_data loads other things which are part of a mine, such as objects (robots, powerups, etc.), initial player position information, etc. Beginning at location 0 in the RDL file: int sig // signature bytes == 'PLVL' (in order 'L' 'V' 'L' 'P') int version // set this to 1 int minedata_offset // offset in file of start of mine data int gamedata_offset // offset in file of start of game data int unused // unused From location minedata_offset: byte version always = 0 short Num_vertices number of vertices in this mine short Num_segments number of segments in this mine Num_vertices vertex structs. A vertex struct is defined as three fixed point numbers. A fix is 32 bits. The low 16 bits is fractional, the high 16 bits is the integer. Num_segments segment structs. A segment is a variable size structure. To understand the format, it is necessary to read the source code included with this document. The function load_mine_data_compiled_new reads a variable sized segment from the "rdl" file and stores it in the internal segment struct. The internal segment struct is described in another section below. From location gamedata_offset: short signature // bytes 05h, 67h short version // 0019h (we're at version 25 for release...) int game_fileinfo_size // 0077h char mine_filename[15]; // for example, "Lunar Outpost" int level; int player_offset; int player_sizeof; int object_offset; int object_howmany; int object_sizeof; int walls_offset; int walls_howmany; int walls_sizeof; int doors_offset; int doors_howmany; int doors_sizeof; int triggers_offset; int triggers_howmany; int triggers_sizeof; int links_offset; int links_howmany; int links_sizeof; int control_offset; int control_howmany; int control_sizeof; int matcen_offset; int matcen_howmany; int matcen_sizeof; short Num_pofs number of Polygon Object Files char Pof_names[Num_pofs][13] name of each pof file From object_offset (read above): object Objects[object_howmany] static object info for each object. See object struct. From walls_offset (read above): wall Walls[walls_howmany] static wall info. See wall struct. From doors_offset (read above): active_door ActiveDoors[doors_howmany] See active_door struct. From triggers_offset (read above): trigger Triggers[triggers_howmany] From control_offset (read above): control_center_trigger Control_center_triggers[control_howmany] From matcen_offset (read above): matcen_info RobotCenters[matcen_howmany] Internal Segment Struct -------- ------- ------ typedef long fix; typedef struct vms_vector { fix x, y, z; } vms_vector; typedef struct uvl { fix u,v,l; } uvl; typedef struct side { byte type; // tri_edge: 1 = quad, 2 = 0:2 triangulation, 3 = 1:3 triangulation ubyte pad; // keep us longword alligned short wall_num; // Index into Walls array, which wall (probably door) is on this side short tmap_num; // Index into array of textures specified in bitmaps.bin short tmap_num2; // Index, as above, texture which gets overlaid on tmap_num uvl uvls[4]; // uvl coordinates at each point vms_vector normals[2]; // 2 normals, if quadrilateral, both the same. } side; typedef struct segment { side sides[6]; // 6 sides short children[6]; // indices of 6 children segments, front, left, top, right, bottom, back short verts[8]; // vertex ids of 4 front and 4 back vertices short objects; // index of objects in this segment ubyte special; // special property of a segment (such as damaging, trigger, etc.) byte matcen_num; // which center segment is associated with, high bit set short value; // matcens: bitmask of producable robots, fuelcenters: energy given? --MK, 3/15/95 fix static_light; // average static light in segment short pad; // make structure longword aligned [Too bad we didn't put this before static_light...MK, 3/15/95] } segment; The 8 vertex indices in the verts array define the 6 sides of the segment. The following shows which vertices form which side. Vertices are oriented counter-clockwise looking at the side from the outside of the segment. left 7,6,2,3 top 0,4,7,3 right 0,1,5,4 bottom 2,6,5,1 back 4,5,6,7 front 3,2,1,0 So, for example, if the verts array = 10, 11, 12, 13, 14, 15, 16, 17 then the right side is made up of the vertices 10, 11, 15, 14. These vertices (10, 11, 15, 14) are indices into the global Vertices array. Format of Mission Files ------ -- ------- ----- Levels are organized into missions which are specified in a "msn" file. (The default mission, "Descent: First Strike" is built into the executable and does not have a corresponding mission file.) The file "chaos.msn" defines the five level anarchy mission which is part of the registered version. Here is the complete text of the file "chaos.msn": name = Total Chaos ;any name you want type = anarchy ;can be "normal" or "anarchy". Omitted means normal num_levels = 5 ;number of normal levels chaos1.rdl ;level filename 1 chaos2.rdl ;level filename 2 chaos3.rdl ;level filename 3 chaos4.rdl ;level filename 4 chaos5.rdl ;level filename 5 It should be pretty self-explanatory. All the "rdl" files are present in the file "chaos.hog". Here's a more interesting mission. Note that it contains a secret level named "levels1.rdl" which is attached to level 10. name = Destination Saturn ;any name you want type = normal ;can be "normal" or "anarchy". Omitted = normal num_levels = 15 ;number of normal levels level01.rdl ;level filename 1 level02.rdl ;level filename 2 level03.rdl ;level filename 3 level04.rdl ;level filename 4 level05.rdl ;level filename 5 level06.rdl ;level filename 6 level07.rdl ;level filename 7 level08.rdl ;level filename 8 level09.rdl ;level filename 9 level10.rdl ;level filename 10 level11.rdl ;level filename 11 level12.rdl ;level filename 12 level13.rdl ;level filename 13 level14.rdl ;level filename 14 saturn15.rdl ;level filename 15 num_secrets = 1 ;number of secret levels levels1.rdl,10 ;get to first secret level from level 10 Format of the Hog File ------ -- --- --- ---- A hog file has the following format: <header> The constant bytes: 44h, 48h, 46h Following the header are zero or more files in the following format: <name> 13 bytes, terminated by 0, padded, if necessary, to 13 bytes <size> 4 byte size <data> <size> bytes of data comprising the file <name> next file in the hog file etc.