which is the solid modeling kernel based on csg

hi all!!

which is the solid modeling kernel which uses csg algorithms??

both parasoid and acis are based on b-rep...
is there any such modeler availabe which is based on csg???

if not ( that is my sure speculation) then can we say that csg
representation is obsolute..
i posted one earlier message regarding csg and brep and someone told
me that in autocad we can build the object using csg
operations(union,add,and subract etc..).but autocad is based on acis
kernel which uses brep representation..
now i am more confused..
so how will one differentiate between building a model using csg
techniques and storing them in brep...

regds,
yogesh joshi

 

You better look for "construction history" instead of "csg". Today the
ability to handle freeform NURBS surfaces is a must even for
low-priced products, and when you already have the surfaces then you
can build the solids from them. You will hardly find anymore a "real"
csg modeller which only enables to construct solids from primitive
bodies (as good old AME did in AutoCAD R12).

Solid Thinking (http://www.gestel.it) is a sample for a product which
shows the complete construction tree and lets you browse through it.

Tom Berger

 

Constructive solid geometry (csg) let you CONSTRUCT a solid by combining
basic shapes.
Boundary representation (brep) rather descibes the RESULTing body in terms
vertices, edges and faces.
Kernels basically build a brep from a csg description while feature
recognition tools do the reverse.
Autocad calls acis csg functions directly, while feature-based CAD in fact
translate the feature tree into a sequence of csg operations. By doing this
smartly, they can avoid rebuilding the whole body from scratch when a
parameter is changed, do rollback and such things. This is why csg is
considered obsolete in end-user tools, but still very important in kernels.

 

Yogesh,

CSG is a construction methodology, not kernal level mathematical
representation.

Some very early 3D CAD systems (pre 1985) used CSG construction exclusively.
The last one I had any experience with was IDEAS V6i (pre master series).
Even then, 1987, the models were represented by NURBS faces and boundary
curves. I seem to remember a German program, same time frame, that claimed
to represent solids without surface information. I don't remember the name,
but I believe they were affiliated with H.P.


Regards

Mark