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[MineCrak]

* There have been indications from Jeb & notch that there will be a lot of differences in map features for version 1.8, to the point where he recommended people wait for 1.8 before starting new maps. Hopefully the functional basics of the method I will describe can be made to be in place before 1.8 drops on us. I doubt many of us want to redo everything we've built, again..

Introduction

Hello. I would like to propose an overall method for accurate updating of old map chunks to new game version features (ore, plants, dungeons etc) without losing the changes a person has made within those chunks (user generated content), and doing so easily without needing to spend forever hand-splicing every block & detail manually with MCEdit (Fantastic tool btw). This tracking method could also be used right from the start with a fresh new map to allow for future clean map updates of it's future "old chunks" with greater ease.

* This will allow the tracking and transfer of all user modified blocks & content (not any unmodified blocks even in same chunk), including inventory etc, to a new Minecraft version of the same world seed via a simple coordinate difference map (Shadow map). - Allowing you to fully experience the benefits that each new version of the terrain & feature generator will provide while keeping every single block & item that you have worked so long and hard to customize. "The world will change around you!".

I am not able to do this dev work at this time and am hoping that there will be other talented souls out there able and willing to start implementing the base tools needed for this, or adding to their already existing tools the compatibility with said tools/features/functionality.

The overall concept involved that will make this ideal possible is actually very simple. I will discuss an interim version of this concept that will allow people with already existing old maps the possibility of accomplishing this goal, even if not absolutely perfectly, as well as how this idea if used from the very start of a new map could allow for easy seemless updating with each game version update.

[Edit] My original purpose for this was for SSP Single player usage, however; it should be possible to accomplish the same thing for SMP Multi-player servers as well.

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Needed

• Shadow-Map file format/structure ("shadow.map", ".sdo" ?)

• Tool for creating a Shadow-map by looking at difference between a current map with user content and a clean unaltered map with same seed generated by same version of Minecraft as the original map.

• Tool that uses a Shadow-Map to merge user content from original map with a clean unaltered map of the same seed generated by a newer version of Minecraft.

• A Shadow-Map mod that will live-update the Shadow-Map with locations of new user content as it is made, and create a new blank Shadow-Map if one is not already present (for new worlds). It could also eventually include an in-game Shadow-Map Editor.

• A Visual Shadow-Map editor for helping with creation of shadow-maps of old maps or just keeping terrain features etc between versions.

* With the functionality of these tools, separate or all-in-one, it will finally be possible to Truly update our maps fully to include the new version terrain features in our "old" chunks, and do so with far greater ease.

Below is a more indepth explanation of how these tools would need to work and how they could be used:

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Shadow-Map

* The Core of this method is a simple standardized binary difference file/map, which I will call a "Shadow Map" and will be in a separate file than the main map files and will be far smaller. Each block of the coordinate grid would be represented with a 0 or 1. Any block stored as 1 would mean that there is a user made change at that location on the normal map, it doesn't matter what that change is. 0 would represent blocks still in their original seed-state. This would not in any way be a copy of the normal map, it just tracks grid locations where user changes occurred.

- The map seed would also be stored in this file, preferably near the beginning of the file. And if it is known, the original game version # that generated the original map should have a place where it can be stored, and also the ability to mark it as unknown but before or after a certain version. It would also be good for it to list the most recent game version that this shadow-map has been synced with. Also, the current spawn coordinates could be stored near the beginning as well, and updated as needed.

-- With an accurate shadow-map a tool could be used to merge a newly generated world file (of the same seed) with an old map, transplanting only blocks changed by the user in the old map over the terrain of the new map. So all the new terrain and map features of the newest game version would perfectly coexist with the user-made elements of the old map (same seed).
- This would be far faster as well as more accurate than hand-editing every detail in MCEdit, though for old maps it would be very useful to have a 3D shadow-map editor for basic fixes and such. Such an editor would also be useful for when the new terrain causes the loss of waterfalls and such which were originally a default part of the terrain.

There would be a section in the shadow-map file for a simple chunk map (only chunks where there are user changes would be a part of this simple (0&1) chunk map, and another for the world block grid map. Each section would house the appropriate type of shadow map for the normal realm as well as for the Nether and be compatible with the addition of any new realms that might be added in new game versions (Sky realm etc).

- The chunk-map would make it easier for a user or an external tool to quickly see which chunks of the seed will need to be generated in a new seed-map before a merge.

This Map file would reside inside of the World folder for which it serves as a Shadow Map, but in it's own file separate from the normal maps files, making it compatible with everything else without causing any irreversable conflicts.

* There should be one standardized format for this shadow-map file so that various tools and editors can all easily make use of it, perhaps even for things that haven't been thought of yet. If the file is made so that a value other than 0 & 1 is able to be stored for each grid block then it should be standard for any value > 0 to be interpreted as 1 when being read in "Simple-ShadowMap Mode", thus preserving backward compatibility for original and basic tools and uses. Perhaps the file extension could be ".sdo" or the filename could be "shadow.map" (just some ideas).

- Perhaps this is a way that non-standard mod-blocks could be tracked and filtered out if the affecting mod ceases to be supported, yet allow the map as a whole to still be used in future game versions (those blocks could hold a value of 2 instead of 1 for instance).

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Shadow-Map Mod

* For a fully developed version of this system there would be a "Shadow-Map Mod" in place which would modify the shadow-map whenever the user makes a block change to the map in-game. Thus allowing an accurate on-the-fly shadow map to be constructed or added to. The mod could be made to work with a pre-made shadow map placed into the world folder before hand, or generate a new blank one if one wasn't already present (For new worlds).

- Perhaps eventually a "Shadow-Map Mod" could be further developed to include an in-game shadow-map editor of some kind. An in-game editor might not be necessary to begin with though. An external one might be good enough.

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Chunk generation for new seed-maps


When transferring user content to a new version seed map with an already existing and accurate shadow-map, it will be necessary to first create a new seed map with the new game version and force it to generate all of the chunks shown in the shadow-map's chunk map (any chunk with user content). This will also be needed when generating a clean seed map with an old game version in order to generate a Shadow-Map for an old (in-use) map.

Ideally there will eventually be an entirely automated way in which to do this, and a standalone tool will be able to perform the entire map upgrade in one easy go. Until then it may be necessary for the user to be able to view the shadow-map chunk-map in some way and use it to move around in the new seed-map (before merging) until at least all of the required chunks have been generated. Perhaps temporary use of a flying mod could assist with this. Hopefully there will be an easy way to force the chunk generation.

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Making Shadow-Maps for old maps

Making an initial useable and mostly accurate shadow-map for an already existing map made with an older version of the game than you are already using will take a little more work than if you start a brand-new map and start using a "Shadow-Map" mod to create and maintain a shadow-map right from the start.

If you have a map with user content on it you want to keep, but the map was made with the same version of the game as you are currently using, then getting started with a shadow-map should be fairly easy for you.

* First, zip-up or copy that particular world folder and date/time label it. Then you can tell the game to create a new map (be sure to give it the same exact seed as your other world) and name the folder whatever you want but perhaps also add the game version of that seed in parenthesis at the end of the name. Then put the game in Peaceful mode and travel around the map at least as far as you had in the original map, but don't change any blocks. This is to make sure you have at least the same chunks present in the new-seed map as are in the original map (you only need the chunks where you made block changes though). If you have an easier method for doing this then please use it.

- After doing this you would then need to use whatever tool becomes available that can generate a new shadow-map by comparing two maps of the same seed and game version and making the shadow-map based simply on the differences between the two. After the shadow map is made inside of the desired world folder (in this case the original world folder) you would then activate a Shadow-Map mod for that map which would then continue to live-update your new shadow-map with all of the changes you make in-game from then on.

--

For old maps made with a prior version of the game than what you are currently using, creating an initial shadow-map for this map will be a little more involved but worth it once made & maintained. In order to make the most accurate shadow-map possible that requires little or no manual editing you will need a pure (unaltered) copy of the same map seed from the same version of the game as the original map was made with and that has at least the same chunks generated as you have user made content in on the original map. This may mean reinstalling an older version of the game if you have it backed up. If you don't have the older version anymore you may be able to do this using the following tool: MCNostalgia

If you can't recall which game version you originally made the map with but do have an old backup of the map, you can look at the date of the oldest back-up (or unzip it and make it available to the game again and see what the last-played date is for it in the world list) then look at the Minecraft release dates list on the Minecraft wiki in order to narrow down which game version you first made it with. If there is another way to tell for certain which version of the game made the map then please post this method in this thread, thank you!

* First, like before; zip-up or copy that particular world folder and date/time label it. Then reinstall the older version of the game, using MCNostalgia if necessary. Then follow the steps above for creating a fresh unaltered seed map with the same seed as your original map and with at least the same chunks as you have user content in on the original map.

- If the version of the game is from before the version that allows you to enter the seed then you might be able to create the pure seed world by copying your current world folder then deleting everything except for the level.dat file. You would then open that as a map with the old version of the game and it should start rebuilding that seed all over again with the old algorithm.

There is the chance that the current map you have, even though started with an earlier version, may have user content in chunks made with newer versions of the game than the original. As such this method could cause new plants and such to appear on the new Shadow-map as user generated content too. In this case a visual shadow-map editor could come in very useful for clearing out non-user content like that when mastering a clean new shadow-map for your old map.

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* Thank you for reading and considering this proposal! I believe that despite the length of this proposal that the method overall is fairly simple and very worth it for it's intended purpose.

[Remidämiii]

bump

[MineCrak]

Perhaps if just the first tools/functionality could be made for a start (without the mod part), then at least we could do a good one time refresh of our maps with the next update.

• Shadow-Map file format/structure ("shadow.map", ".sdo" ?)

• Tool  for creating a Shadow-map by looking at difference between a current  map with user content and a clean unaltered map with same seed generated  by same version of Minecraft as the original map.

• Tool  that uses a Shadow-Map to merge user content from original map with a  clean unaltered map with same seed generated by a newer version of  Minecraft.

The last one below would be useful too, but if at least we had the first ones above then we could get something going. How difficult would the above items be to accomplish?

• A  Visual Shadow-Map editor for helping with creation of shadow-maps of  old maps or just fixing terrain features etc between versions.

[MineCrak]

Any thoughts on this? Or any idea which known devs around here would be capable of this? Perhaps the writer of WorldEdit or MCEdit?

[Quillionaire]

If this can be pulled off to even 1/10th of the extent you've described, this will be a game-changing (literally!) tool for everyone.  I, for one, hope that this project can get off the ground.

[aXu]

This is a great idea. If I had time, I'd definedly work with this... But I need to finish other work first!

Not entirely sure how it would turn out if they do major overhaul on map generator like when biomes came, the terrain changed totally.

[MineCrak]

aXu, on 02 July 2011 - 02:42 PM, said:

This is a great idea. If I had time, I'd definedly work with this... But I need to finish other work first!

Not entirely sure how it would turn out if they do major overhaul on map generator like when biomes came, the terrain changed totally.

Thanks! True enough.

But at the very least, and this is no little thing, it would provide an easier way to "select" everything you have made and own with one click and transplant it into the new "alternate reality" version of your world or even someplace else. That's where having a shadow-map editor would come in handy; you could "delete" the parts of the shadowmap that are clearly reflecting terrain modifications you made versus structures you made. And with proper MCEdit integration the whole thing could be made into a schematic that you could then edit in other ways too.

[aXu]

One possibility would be to save shadow maps as normal worlds. All unmodified blocks could have ID 255. Benefits are considerable: all current map editors and viewers would support it without modification and you don't need your original world to migrate to new world. It would also work as a backup of your world.
Biggest sacrifice would of course be the size of shadow map, but with today's HDDs that isn't a big problem. I guess these worlds get gzipped more efficiently being mostly same block IDs and no entities need to get saved with exception of paintings.

[MineCrak]

aXu, on 03 July 2011 - 12:10 PM, said:

One possibility would be to save shadow maps as normal worlds. All unmodified blocks could have ID 255. Benefits are considerable: all current map editors and viewers would support it without modification and you don't need your original world to migrate to new world. It would also work as a backup of your world.
Biggest sacrifice would of course be the size of shadow map, but with today's HDDs that isn't a big problem. I guess these worlds get gzipped more efficiently being mostly same block IDs and no entities need to get saved with exception of paintings.

Nice! That's a very good point. It may well be worth it at this point in order to accomplish the main goal. And yeah you're right, it should compress very well indeed.

aXu, on 03 July 2011 - 12:10 PM, said:

and you don't need your original world to migrate to new world.

Yes and no; as I document above, when a shadow-map starts being constructed at the start of a new world then it will not be necessary to have an original clean copy of that world in order to migrate later on, but only because there is a complete shadow-map in sync from the start.

However; when taking an already existing built on map which does not have a shadow-map, a pristine (or at least as close to it as possible) version of that world map in it's original version will be needed in order to provide the best possible chance of creating an accurate shadow-map for it, though a clean seed made by any beta pre-1.8 version will probably be better than nothing to start the process with.

A little shadow-map editing + chunk pruning after that will likely be enough to clear out random materials left in newer chunks made by in between game versions. Since most of the shadow-map will be empty any deviations scattered around should be easy to spot. Heck, an algorithm could probably be made which could auto-prune shadow-map "noise" in border chunks and such.

You are sooo right though about how much easier all of this will be for people to implement if the shadow-map is constructed in the same format as the normal map!

Thanks for your help!

[randalpik]

Not updating to 1.8 until this comes out.

[aXu]

I don't believe this would help with transition to 1.8... So many new things, and biome algorithms will be changed. On the other hand, it COULD work. Dunno what's gonna happen if your backyard has a dungeon or your frontdoor opens to big drop trough ravine It'd be cool, actually!

So yea, we need to get this done. I don't know if there will be a good reason to use this after 1.8, but I hope Notch will continue to add elements to the generator as well.

[MineCrak]

randalpik, on 23 July 2011 - 01:55 AM, said:

Not updating to 1.8 until this comes out.

LOL, Thanks for your support!

Well, I guess we have at least another month or so before 1.8 drops on us so it could still be made.

Really, at this point, I'd just settle for a simple tool that a person could use to make & edit a manual Diff-map (Shadow Map), then use that Shadow-map as the filter to merge two worlds with (Primarily two release versions of the same seed). I'm no longer worried about the live-mod version, though I still think it could have uses.

I think that the tool aspect I just spoke about would have use for a lot of people, even potentially after 1.8 if you think about what that tool does. It doesn't seem to me that that would be the most complicated thing to make for some people, but they seem to want to wait until the mythical source code release, which won't be until after 1.8 sometime at the earliest, if ever really...

I'm starting to think that I will just have to spend a month turning every little piece of my dominion into MCEdit Schematics then pasting them into the new world in just the right places... I guess I'm exaggerating, I don't know since I haven't done something on that scale before.

But considering there isn't even a single +1 for this idea compared to ideas like "[REQ] TOILETS IN MYNEKRAFT!!!" having 33, well, I'm not holding my breath and I'm not going to ask any of you to.

Perhaps If I had posted this back in January it would have gotten some traction.

aXu, on 23 July 2011 - 07:06 AM, said:

I don't believe this would help with transition to 1.8... So many new things, and biome algorithms will be changed. On the other hand, it COULD work. Dunno what's gonna happen if your backyard has a dungeon or your frontdoor opens to big drop trough ravine It'd be cool, actually!

So yea, we need to get this done. I don't know if there will be a good reason to use this after 1.8, but I hope Notch will continue to add elements to the generator as well.

True to some degree, but other than ravines and such it sounds more like Biomes/weather will be the largest surface effect change in normal areas since Jeb said notch wants to expand the size of biomes. Your tree farm today might be your Christmas tree farm tomorrow, heh heh. But then we've had that before already.

I agree, I believe there would still be use for the tool, it actually performs a universal sort of function.

In any case, thank you guys for your support!

* There's always the chance that I might just become a Guru or hermit on a mountain top with a view at y=256 or 512 or 1024 or something.

[aXu]

MineCrak, on 27 July 2011 - 03:38 PM, said:

Really, at this point, I'd just settle for a simple tool that a person could use to make & edit a manual Diff-map (Shadow Map), then use that Shadow-map as the filter to merge two worlds with (Primarily two release versions of the same seed). I'm no longer worried about the live-mod version, though I still think it could have uses.

What if I told you I have been planning & testing stuff this week for a simple tool?
No promises, though (I'm quite busy now)

[MineCrak]

aXu, on 27 July 2011 - 07:48 PM, said:

What if I told you I have been planning & testing stuff this week for a simple tool?
No promises, though (I'm quite busy now)

  Zoinks!!

I'll be right back. < goes to window to see if it's snowing > It's not snowing, but I swear you said that Christmas is coming early?!

Are you kidding me? That's Fantastic!! You are sneaky!

Wow aXu, Thank you. However this goes I really appreciate you working on this for everyone! You sure kept your cards close to your sleeve on this, heh heh. I have at least a couple or so worlds that I will try to update from really old version release saves into 1.7.3 seed worlds as tests with this, and whatever else happens this will breath new life into those Worlds which I have fond memories of. I'm certain that there will be a LOT of people who would love to do the same if they were able to.

I completely understand you being busy! So I won't pester you or anything. But if you need a beer just let me know where to send it.

* Also; I'm so glad that Randall will be able to upgrade to 1.8!

[randalpik]

Woot, I hoped this project would get off the ground

I've been talking with the people on my own multiplayer server, and their opinions are divided. Some of them want to use this tool when 1.8 comes. Others want to get a new map entirely. Others want to get a new map now and use this tool to import it to 1.8.

I personally want to keep the old map. A couple months of work has gone into it. We've weathered the updates to 1.6 and to 1.7. We've built some crazy stuff-- a legitimate 47x47 cobblestone sphere with redstone torches flashing around it, a legitimate working 7-segment display counter, a legitimate 3,000 block long minecart track that connects 4 different amazing towns, a legitimate 100x100 block storage room-- the list goes on. But even so, some of my players want to start fresh, even the guy who built the huge storage room.

I still have no clue what I'm supposed to do, because the votes are about even. But if this tool comes out before 1.8, then it'll be easier to convince my players one way or the other.

P.S. I am *obviously* not trying to advertise for my server! Heh heh.

[nickguletskii]

Thanks for giving me a really good idea. I plan on implementing this a bit differently though - I will store changes done to the world since the generation and then do a regeneration of it. Your method would take up a lot of space, because most of the chunks generated don't get modified by the player.

Thank you very much for giving an idea that isn't like those "HERP DERP ADD REDSTOAN TOOLZ" ideas. I like the fact that I will be adding something useful, not fun. I always prefer making useful modifications rather than fun.

[MineCrak]

nickguletskii, on 30 July 2011 - 09:42 PM, said:

Thanks for giving me a really good idea. I plan on implementing this a bit differently though - I will store changes done to the world since the generation and then do a regeneration of it. Your method would take up a lot of space, because most of the chunks generated don't get modified by the player.

Thank you very much for giving an idea that isn't like those "HERP DERP ADD REDSTOAN TOOLZ" ideas. I like the fact that I will be adding something useful, not fun. I always prefer making useful modifications rather than fun.

Thank you, but are you talking about my proposal in the OP? I think you just described what I wrote up there. A Shadow-map only stores the coordinates of where changes have been made to the map/world. It can't get any smaller or take up any less space than that.

I'm not exactly sure how aXu will be implementing the Shadow Map & Tool portion of the proposal, but it still is only about storing info on the user changes made to the map, so that the user changes can be recreated on a fresh version of the seed without affecting new ore distibutions and such. Even what used to be "old" chunks will now be fresh with whatever new ores and such have been added to the new Terrain Generator.

* It almost sounds like you are saying that you will be implementing the Mod portion of my proposal? Because, as described in the OP, I believe it does what you described. If that is what you are making then YAY! Both the Mod AND the TOOL Portions of the Proposal will be getting made!

Or is your implementation different in some way? If there is a difference I would just like to understand it so that I would know what tool/mod options will exist for use based on this.

I appreciate your sentiment; There are some really useful tools that could still be made to enhance our use and enjoyment of this game. I look forward to seeing what you make!

MineCrak, on 10 June 2011 - 11:12 AM, said:

This  tracking method could also be used right from the start with a fresh  new map to allow for future clean map updates of it's future "old  chunks" with greater ease.
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*  This will allow the tracking and transfer of all user modified blocks  & content (not any unmodified blocks even in same chunk), including  inventory etc, to a new Minecraft version of the same world seed via a  simple coordinate difference map (Shadow map).
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as well as how this idea if used from the very start  of a new map could allow for easy seemless updating with each game  version update.
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A  Shadow-Map mod that will live-update the Shadow-Map with locations of  new user content as it is made, and create a new blank Shadow-Map if one  is not already present (for new worlds). It could also eventually  include an in-game Shadow-Map Editor.
----
*  The Core of this method is a simple standardized binary difference  file/map, which I will call a "Shadow Map" and will be in a separate  file than the main map files and will be far smaller. Each block of the  coordinate grid would be represented with a 0 or 1. Any block stored as 1  would mean that there is a user made change at that location on the  normal map, it doesn't matter what that change is. 0 would represent  blocks still in their original seed-state. This would not in any way be a  copy of the normal map, it just tracks grid locations where user  changes occurred.
----
- Perhaps this is a way that non-standard  mod-blocks could be tracked and filtered out if the affecting mod ceases  to be supported, yet allow the map as a whole to still be used in  future game versions (those blocks could hold a value of 2 instead of 1  for instance).
----
Shadow-Map Mod

*  For a fully developed version of this system there would be a  "Shadow-Map Mod" in place which would modify the shadow-map whenever the  user makes a block change to the map in-game. Thus allowing an accurate  on-the-fly shadow map to be constructed or added to. The mod could be  made to work with a pre-made shadow map placed into the world folder  before hand, or generate a new blank one if one wasn't already present  (For new worlds).

- Perhaps eventually a "Shadow-Map Mod" could  be further developed to include an in-game shadow-map editor of some  kind. An in-game editor might not be necessary to begin with though. An  external one might be good enough.
----

[MineCrak]

randalpik, on 30 July 2011 - 06:24 PM, said:

Woot, I hoped this project would get off the ground

I've been talking with the people on my own multiplayer server, and their opinions are divided. Some of them want to use this tool when 1.8 comes. Others want to get a new map entirely. Others want to get a new map now and use this tool to import it to 1.8.

I personally want to keep the old map. A couple months of work has gone into it. We've weathered the updates to 1.6 and to 1.7. We've built some crazy stuff-- a legitimate 47x47 cobblestone sphere with redstone torches flashing around it, a legitimate working 7-segment display counter, a legitimate 3,000 block long minecart track that connects 4 different amazing towns, a legitimate 100x100 block storage room-- the list goes on. But even so, some of my players want to start fresh, even the guy who built the huge storage room.

I still have no clue what I'm supposed to do, because the votes are about even. But if this tool comes out before 1.8, then it'll be easier to convince my players one way or the other.

P.S. I am *obviously* not trying to advertise for my server! Heh heh.

Yeah, I think a LOT of servers are going to have some serious decisions to make when 1.8 roles out. Is your server a bukkit server? You could use multi-worlds to keep the refreshed version of your current world as well as have a new one, and have a giant portal between them .

You could even do something unique with the terrain or physics in the new one (or change ore distribution) so that there would be a good reason to go back and forth between both worlds.

[nickguletskii]

MineCrak, on 30 July 2011 - 10:53 PM, said:

Thank you, but are you talking about my proposal in the OP? I think you just described what I wrote up there. A Shadow-map only stores the coordinates of where changes have been made to the map/world. It can't get any smaller or take up any less space than that.

I'm not exactly sure how aXu will be implementing the Shadow Map & Tool portion of the proposal, but it still is only about storing info on the user changes made to the map, so that the user changes can be recreated on a fresh version of the seed without affecting new ore distibutions and such. Even what used to be "old" chunks will now be fresh with whatever new ores and such have been added to the new Terrain Generator.

* It almost sounds like you are saying that you will be implementing the Mod portion of my proposal? Because, as described in the OP, I believe it does what you described. If that is what you are making then YAY! Both the Mod AND the TOOL Portions of the Proposal will be getting made!

Or is your implementation different in some way? If there is a difference I would just like to understand it so that I would know what tool/mod options will exist for use based on this.

I appreciate your sentiment; There are some really useful tools that could still be made to enhance our use and enjoyment of this game. I look forward to seeing what you make!

Actually, wait, I have just realised that a shadow map like you described would only use bits, meaning that the file would be around 4 kilobytes in size per chunk... And no duplicate modifications. Sorry, it was really late when I was writing my previous post. Your way is much better.

[MineCrak]

nickguletskii, on 31 July 2011 - 09:25 AM, said:

Actually, wait, I have just realised that a shadow map like you described would only use bits, meaning that the file would be around 4 kilobytes in size per chunk... And no duplicate modifications. Sorry, it was really late when I was writing my previous post. Your way is much better.

Cool. I'd love to know what you do with this, so I can use it on my maps too.

Actually; further up in the thread aXu describes a variation on how to make the shadow map, which is how I'm guessing he will do it, that uses a regular map-type format so that it is more compatible with map-editing tools but would be highly compressible. Take a look and see if it would work for you. But also please look at my response below his for some clarification.