Hi Pierre, Thanks a lot for your feedback. About remark A: I'm also more interested in real time 3D and if I had had more time to spend, the algorithms you're talking about would be there already. I mostly participated in the design, not algorithms. Barend worked a lot on algorithms so he brought his part, that is GIS. This doesn't prevent from bringing other application domains. We constantly made sure that the design allows to add that easily. Also, note that we mentioned a project structure based on extensions. The kernel is "agnostic" regarding any precise application domain, while extensions allow to propose more specific stuff. Although the limit between both is sometimes hard to define, this normally avoids having many people wanting to see in the kernel the algorithms *they* are interested in. So typically, some of the things you are asking for could be included in the kernel (lines, rays...) and other ones would rather come as specific extensions (frustums, meshes...). Hope this makes sense to you? About remark B: Good point about the fact that documentation is more user-oriented than extender-oriented, this is something we should try to improve. Regarding the user part, I sincerely think that what we have is sufficient (I mean, adapting legacy geometries and using algorithms on them). Regarding the extender part, it will indeed require us to give better insight about the actual design. However, I would like to be clear about this sentence: "can it be extented by someone who do not use more templates than the stl". The answer is no. The library has been designed to be easily *used* by someone who basically doesn't know template. But to extend it (e.g. add mesh-related concepts and implement algorithms on them), knowledge is obviously required. You'll have to specialize some traits, play with tags, etc... the point is rather to ensure that the design gives sufficiently precise directions and instructions to keep extensions consistent. About remark C: Indeed, several persons have made the same remark already :-) Regards Bruno