[Bf-committers] Report of HE Mesh
jlp at nerim.net
Mon Mar 7 00:14:28 CET 2005
Le 6 mars 05, à 23:13, joeedh a écrit :
> joeedh wrote:
>> Hi. Here is the current feature (and bug) list of HE Mesh.
That's good news. But the first thing is still to define exactly what
you want to support, there is many variations on the half-edge :
- Closed mesh only or open ?
- if open, allowing inner boundaries ?
- genus order supported ?
- holes in faces ?
- face in face ?
- genus handles starting from a face in face
- multiples shells, multiples components (mandatory, but handling
depend if we support holes in faces) ?
- exceptional vertexs ? (eg 2 pyramids joined by the point, handling
change if hole in faces or not)
**- supporting reflexive half edges ( edge with same face on each side,
ie tube with one seam) ?
**- supporting tube with no seam ? ( from a topological point of view,
if open at each end, it is the same as a face with hole, but change the
requirements on structs if not)
- degenerates cases (eg edge with no face, isolated vertices)
And i forgot certainly more. For making things even more complex all
those features are not independant
(the 2 marked ** would cause problems to other parts of blender i think)
Considering how half-edge work, it is very important to define that
from the start.
Both the structs to use and the tools to manipulate them will change
according to those choices with rapidly increasing complexities. Once
one level of support is defined, it will be hard to change to more
The difficult point in half-edge is to validate the datas, it is
important to use only low level Euler operators which insure a valid
mesh is still valid after using them. Those operators and the
validation formula changes with the kind of half-edge mesh. Any
operation can be expressed as a combination of those operators
Also, do you want to make room for further expansion, like
multi-resolution meshes ?
> BTW, do you think I really have to have the renderconverter code
> working before posting testing builds for the users? That's really
> and truly the only major hurdle right now: You cannot render what you
testing build forum is for finished or at least mostly completed work
imho. and render code is the most important
As i said before, i will help you on that project. i will prepare a doc
(this week i think) listing the options that i think possible.
Then you will have to provide an up to date patch file, i can (with
others) analyze and give you feedback of. but without first defining
completely the goal, i cannot do anything.
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