[Bf-committers] Mesh surface and volume calculation

[Jonathan Merritt]

Franz Münz wrote:

>The argorithms are VERY simple. For the volume read this:
>
>http://www.gamedev.net/community/forums/topic.asp?topic_id=279606 
>(see last post; provided by z3r0_d in blender.org forum)
>  
>

OK - thanks for that.  It's what I'd refer to as a "Gaussian surfaces" 
technique (after the same concept used by Gauss' law in 
electromagnetism).  However, I think it would be very useful to document 
these algorithms properly (with cool 3D diagrams, etc :-) in the Blender 
documentation at the same time as the code is written.  It may not seem 
particularly important at the time, but it allows people who can 
understand the maths to confidently use these functions, and provides 
something that can be referred to academically if necessary (which can 
be very important!).

Just as an example, take the "lens" setting of the Blender camera.  In 
the reference documentation it says: "This number is derived from the 
lens values of a photo camera: '120' is telephoto, '50' is normal, '28' 
is wide angle."  How to convert this lens number into an actual 
field-of-view or focal length is not documented!  I keep having to 
re-assure myself by going back to the code every time I need to make the 
conversion.  I'm going to try to improve this soon by submitting the 
actual formula and a diagram explaining "field of view" and "focal 
length".  I think it would be very good for the original authors to 
contribute this kind of information when new code is written though.

Jonathan Merritt.