about Convex Decomposition

[smallping]

I am a new beginner using newton dynamics.

And I want to use compound collision, so I must use convex decomposition for my concave models.

My models are *.obj file format coming from CAD system.

I read some articles about this in this forum, but I do not find any information I can realize it.

Can somebody help me to explain how to realize it ?

My email is : goodglxpj@hotmail.com

Thank you very much.

[Julio Jerez]

what are you doing?

[smallping]

I want to use compound collision in Newton Dynamics.
Because my models are concave shape.
So I must use convex decomposition.

Can somebody give me some help about convex decompositon.

[JernejL]

this can get you started, i used this library a while ago: http://codesuppository.blogspot.com/200 ... ition.html

[Julio Jerez]

There is not convex decompsition in newton at this time. I promise I will add it to the NewtonMesh, but as of today it is an unfinished work in progress.

I beleive people use (Delfi) a free public utility that create the decomposition, you can problebly use that and feed the output data to the Compound collision in Newton.
Other than that, another solution if you do not want to go though the problem of getting different APPs just to get the collison modelled.
is to use a Physics library that already does Convex decomposition an uses polygon soup collision.

[JernejL]

I did make http://mathpudding.com/temp/extconvex.rar library, but it only comes with a delphi example - which is very simple that it could be translated to C/C++ by anyone:

Code: Select all

program ExtConvex;

uses
  sysutils;

{$R *.res}

procedure convexify(a, depth, cpercent, ppercent, maxv, skinWidth: integer; filen: PChar); cdecl; external 'DecomposeSample.dll';

begin
if fileexists(ParamStr(6)) = false then exit;

convexify(0, strtoint(ParamStr(1)), strtoint(ParamStr(2)), strtoint(ParamStr(3)),
strtoint(ParamStr(4)), strtoint(ParamStr(5)), pchar(ParamStr(6)));

end.


This is all i have, but smallping doesn't seem to understand it and i can't translate it to c for him to use (he asked me in a private message), since i don't work with c++

Anyway, if he doesn't understand that pascal syntax the ratchliff's original code would be probably easier for him to use directly..

[Carli]

I did make http://mathpudding.com/temp/extconvex.rar library, but it only comes with a delphi example - which is very simple that it could be translated to C/C++ by anyone:

Code: Select all

program ExtConvex;

uses
  sysutils;

{$R *.res}

procedure convexify(a, depth, cpercent, ppercent, maxv, skinWidth: integer; filen: PChar); cdecl; external 'DecomposeSample.dll';

begin
if fileexists(ParamStr(6)) = false then exit;

convexify(0, strtoint(ParamStr(1)), strtoint(ParamStr(2)), strtoint(ParamStr(3)),
strtoint(ParamStr(4)), strtoint(ParamStr(5)), pchar(ParamStr(6)));

end.


This is all i have, but smallping doesn't seem to understand it and i can't translate it to c for him to use (he asked me in a private message), since i don't work with c++

Anyway, if he doesn't understand that pascal syntax the ratchliff's original code would be probably easier for him to use directly..

I translate for you:

Code: Select all

typedef void cdecl (*Tconvexify)(int a, int depth, int cpercent, int ppercent, int maxv, int skinWidth, char* filen); // type definition of the function signature
Tconvexify convexify; // the function as a variable
unsigned int dll = LoadLibrary("DecomposeSample.dll"); // load the DLL
convexify = (Tconfexify) GetProcAddress(dll, "convexify"); // load the function


c++ is weird because you cannot link dynamic libraries platform independend but in a world of fences and walls, you will need windows and gates