I'm writing this message to mostly capture ideas/thoughts from last nights IRC discussion before they leave my brain.
The basic idea is to communicate all face (and I think animation data) to the client before play starts. This should improve bandwidth some (no spike in sent data when entering a new map to send images, etc). This also simplifies a lot of code - no need to check to see if images have been sent - this is more relevant if things like embedding images is added. To do this would mean that all clients must do image caching. A problem right now is that to just download information on the 4000 images in use takes measurable amount of time. To fix this, the image numbers on a server would remain constant - new or changed images would get added to the end. Right now, all images are put in alphabetical order, and then assigned numerically. Thus, if a new image starting with A is added, all images after that point have new numbers. So under this scheme, if the server currently had 4126 images, and some new images were added, they would get numbers 4127, 4128, and so on - in this way, images 1-4126 remain the same, so the the client doesn't need to request names and checksum information for those. Likewise, if an image changes, its old entry would get blanked out (a whole in the image numbers), and it put at the end. In this way, when the client connects, it request the highest image number the server has and records that away. If its stored value does not match the number the server reports, it knows from what point to start requesting that new information - so in general it would likely need a fairly small set of new images, and if connecting to the same server, in many cases it would know instantly that it is up to date. For any new images, it could then use askface to fetch them. It might be nice to also allow out of band methods (ftp, http) as an alternative to fetch images - in this case, it would presumably be fetching things the consolidated image files. However, this is more complicated - if only 10 images have changed, I don't want to fetch an image file with 4000 images, so incremental image files would be needed. But if the collect script knows which images have changed or are new, it is a pretty simple matter to put those images into incremental image files. Other thoughts: I've mulled over the idea of using checksums (md5 or something) instead of the current checksum and image name. With this, the server would basically just say 'image 6 checksum is 12ab53....'. The client can then check to see if has an image of that checksum anyplace - if doesn't care where it got it from (different server, part of standard image package, etc), and if so, uses it, otherwise requests it. In some ways, this can be more efficient, because some images have long names. It looks like the current average name length is 12 characters - an md5 would be 16 bytes, but would no longer be needed to send checksum data since that is the checksum, so would be a wash. The problem here is that it is likely we will want to be able include image names in text messages and the like, so we can't get away from names. I'm not sure how good our current checksum method is - it is a 32 bit, but I doubt is especially collision resistant. A current problem with just storing images by image names is you get the case of different servers may have an image by the same name but different contents. This basically means that caching information must be stored per server. While in most cases, these duplicate names are not likely to cause much issue, one could imagine that the names are such that they do cause issues (calling it something like map.111 which is a map meant to display to players as part of a quest). Using good checksums means that the client can basically share images from all the servers it may play against, but we avoid the problem of images of same name. One other random thought: The new login method will be such that no map/image data will be shown until the player logs in and selects a character. What this means is that the client could conceivably do a lot of the image updating while that is happening, and only if not done by the time the login is finished does it have to pop up a notice saying something like 'fetching images' _______________________________________________ crossfire mailing list [email protected] http://mailman.metalforge.org/mailman/listinfo/crossfire
