# My notes on why this fork exists.

I created this clone of the Source SDK years ago so that I could share one commit: 7c61562eb6e1dd1a4fd2a3c4baeadce6e35901b0

I was doing offline procedural map generation in the source engine. I wrote a tool (not available here) that would use rules to piece together collections of smaller maps (rooms and hallways). The resulting map contained only a bunch of func_instance entities (instances of other maps). The instance map that the tool spit out would then be compiled normally.

I discovered a bug in vbsp that was thwarting my goal of generating HUGE maps. I wanted to generate maps that spanned the entire  possible map space.

The tool would calculate stats on each instance to estimate how many could fit in one map, but the results were always turning up wrong. If I flattened the instances into a non-instanced map, compiled that, and then compared it to the compiled map that contained only instances, the results were different. That was surprising because the compile process of a func_instance does exactly the same operation. I spent some time stepping through a compile and verifying each step to find the problem. It turned out there was a bug that prevented func_instance geometry from merging correctly. The instanced brushes' texinfos were built without the func_instance's origin as an offset. To the CSG routines, neighboring brushes could never merge because their textures were always incongruous, even if they actually weren't. 

The overall effect was that two identical instances of the same single brush, when next to eachother but in different func_instances, would never merge. Walls, ceilings, and floors would remain as separate brushes instead of merging together into a single brush. It severely limited how many instances could fit in a map because it would, for example, hit the brush limits very quickly.

My one-line fix, in the previously mentioned commit, fixes that. After this, I was able to cram a stupid number of instances into the final maps.


# Original README

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