Game Development Stack Exchange is a question and answer site for professional and independent game developers. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I haven't posted here before but I came across a problem, when I save a map in Hammer as .bsp it ends up being over 10x bigger than all of the source files put together. I found the source for one map rp_downtown_v2.bsp, which the map is 2mb but when I used the source and compiled it in hammer its 40MB? Why would this be? Any further help will aid thanks!

share|improve this question

migrated from Aug 29 '12 at 19:32

This question came from our site for passionate videogamers on all platforms.

What is hammer? – Phill.Zitt Aug 29 '12 at 15:49
@Phill.Zitt part of Source SDK. This belongs on Gamedev.SE – kotekzot Aug 29 '12 at 17:59
@kotekzot - Okay, that makes things so much clearer. Thanks for that. And agreed, this should be on Gamedev.SE – Phill.Zitt Aug 29 '12 at 18:11
Please add the list of WAD files you have included in your VHE for the map. It might be that you're baking the WAD's in the BSP, and that there are too many of them. – joltmode Aug 29 '12 at 19:42
So what's the actual problem? – Byte56 Aug 29 '12 at 20:18

The BSP file format stores a lot of information in it. For one it takes your brushes from Hammer and performs CSG on them to create all the triangles that are to be rendered. It then calculates other complex information such as planes, edges, surfaces, visibility, etc. that is not part of the source file.

But the largest contributor to the file size would probably be the lightmaps, which are textures used to give the map shadows. Each face in the map will have a lightmap texture, so the more faces you have the more lightmaps you need. Being a texture, they take up a fair amount of space (compared to other binary data).

See this article for more information: Source BSP File Format.

share|improve this answer
Is there any way to obfuscate it? Like fully compile it? Or are you saying there's files inside the bsp that are useless and can be removed? – tincopper2 Aug 30 '12 at 1:55

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.