Lazarus + GLScene

[Kjow]

Hi all,

I'm trying to make a simple Newton 2.0 demo for Lazarus and GLScene, but I have some problems.
First of all, this demo compile and works right by command line (e.g. fpc SDLNewtonBasicDemo.pas ):

// =============================================================================
//
// SDLNewtonBasicDemo.pas
// Very basic demo that shows how to use Newton Game Dynamics.
//
// =============================================================================
// Note : Using Newton 2.xx
// =============================================================================
//
// 2010 by Sascha Willems (www.saschawillems.de)
// Newton Game Dynamics © 2003-2010 by Julio Jerez (www.newtondynamics.com)
//
// =============================================================================

So, I tried to copy some code from it to my "demo", but when compiling I have this error:

Hint: Start of reading config file C:\Develop\fpc\2.5.1\bin\i386-Win32\fpc.cfg
Hint: End of reading config file C:\Develop\fpc\2.5.1\bin\i386-Win32\fpc.cfg
Free Pascal Compiler version 2.5.1 [2010/06/26] for i386
Copyright (c) 1993-2009 by Florian Klaempfl
Target OS: Win32 for i386
Compiling Engine3D.lpr
Compiling main.pas
main.pas(34,14) Hint: Type "TVector3f" redefinition
main.pas(38,14) Hint: Type "TMatrix4f" redefinition
main.pas(92,60) Hint: Parameter "TimeStep" not used
main.pas(92,78) Hint: Parameter "ThreadIndex" not used
main.pas(141,49) Error: Wrong number of parameters specified for call to "ForceAndTorqueCallback"
main.pas(92,11) Hint: Found declaration: ForceAndTorqueCallback(const PNewtonBody,Single,LongInt); CDecl;
main.pas(152) Fatal: There were 1 errors compiling module, stopping

then it point to this row:

NewtonBodySetForceAndTorqueCallBack(NewtonBody, ForceAndTorqueCallback);

Where am I in wrong?

Thank you!

[JernejL]

those types are named same in both newton.pas and glscene's vectors unit.

if you refer to them like var a = newtonunit.tglvector3f you'll no longer have such issues, but the likely cause is, that command line and ide build process use different order of including files in uses clause.

[Kjow]

I renamed types as here:

TVector3fCustom = record
X,Y,Z : Single;
end;

TMatrix4fCustom = array[0..3, 0..3] of Single;

but I think that the problem is here:

main.pas(141,49) Error: Wrong number of parameters specified for call to "ForceAndTorqueCallback"
main.pas(92,11) Hint: Found declaration: ForceAndTorqueCallback(const PNewtonBody,Single,LongInt); CDecl;

with:

procedure ForceAndTorqueCallback(const Body : PNewtonBody; TimeStep : Float; ThreadIndex : int); cdecl;
var
Mass : Single;
Inertia : TVector3fCustom;
Force : TVector3fCustom;
begin
NewtonBodyGetMassMatrix(Body, @Mass, @Inertia.x, @Inertia.y, @Inertia.z);
Force := V3(0, -9.8 * Mass, 0);
NewtonBodyAddForce(Body, @Force.x);
end;

constructor TNewtonBox.Create(pSize, pPosition : TVector3fCustom; pMass : Single);
var
Inertia : TVector3fCustom;
Collision : PNewtonCollision;
begin
...
...
// Finally set the callback in which the forces on this body will be applied
NewtonBodySetForceAndTorqueCallBack(NewtonBody, ForceAndTorqueCallback);
end;

[Stucuk]

Code: Select all

NewtonBodySetForceAndTorqueCallback(NewtonBody, @ForceAndTorqueCallback);

You need @ to turn it into a pointer. The way your calling it is actualy telling the compiler that you want to Run ForceAndTorqueCallback and give its result as a parameter to NewtonBodySetForceAndTorqueCallback. As a pointer the compiler doesn't try to run ForceAndTorqueCallback.

[Kjow]

Thank you!

[Kjow]

Hi again,

I got a cube (GLCube) that falls over a mesh (GLFreeForm), but the FreeForm is static!

Here the code I use, that loads into Newton the mesh:

Code: Select all

GLFreeForm.LoadFromFile(ExtractFilePath(Application.ExeName)+'mesh.obj');

  xT:= 1;
  yT:= 1;
  zT:= 1;
  massT:=0.001;

  IxxT := massT * (1/12) * (yT*yT+zT*zT);
  IyyT := massT * (1/12) * (xT*xT+zT*zT);
  IzzT := massT * (1/12) * (xT*xT+yT*yT);

  static:= NewtonCreateTreeCollision(Newtonworld, 0);
  NewtonTreeCollisionBeginBuild(static);

  test:= TAffineVectorList.create;
  test:= GLFreeForm.MeshObjects.Items[0].ExtractTriangles;

  for i:= 0 to test.Count div 3 do
  begin
    v[0]:= test[i*3 + 0];
    v[1]:= test[i*3 + 1];
    v[2]:= test[i*3 + 2];
    NewtonTreeCollisionAddFace(static, 3, @v[0], 12, 1);
  end;

  NewtonTreeCollisionEndBuild(static, 1); // with optimization

  NewtonBodyStaticMesh := NewtonCreateBody(Newtonworld, static);

  NewtonBodySetMassMatrix(NewtonBodyStaticMesh, massT, IxxT, IyyT, IzzT);
  Newtonbodysetmatrix(NewtonBodyStaticMesh,NewtonImport.PFloat(GLFreeForm.AbsoluteMatrixAsAddress));

  NewtonbodysetUserdata(NewtonBodyStaticMesh,GLFreeForm);
  GLFreeForm.TagObject := TObject(NewtonBodyStaticMesh);

  NewtonBodySetForceAndTorqueCallBack(NewtonBodyStaticMesh, @ForceAndTorqueCallBack);

  test.Free;     

I load this on Form.Create, and everything works right. The GLCube seems to react well/realistic with the mesh.

Now, how can I load a second mesh (e.g. GLFreeForm2), but as dynamic object? I mean that the second mesh should fall, respond to gravity and bounce over first mesh.

Is the code I use right? Can it be optimized?

I'm sorry, but I'm starting now with Newton...

[Stucuk]

Collision Trees are only static objects.

[Kjow]

OK, but how to modify this code to add a dynamic object? (I mean a GLFreeForm, I already added a "dynamic" GLCube, but it isn't a "mesh")

Thank you!

[Carli]

You can use a convex hull to get a dynamic object.

[Kjow]

Do you mean NewtonCreateConvexHullFromMesh or NewtonCreateConvexHull?

However, how to use it?

I don't know how to fill each parameter, e.g.:

dyn:= NewtonCreateConvexHull(Newtonworld, ???, ???, ???, 0.002, 2, NewtonImport.PFloat(GLFreeForm2.AbsoluteMatrixAsAddress));

or

dyn:= NewtonCreateConvexHullFromMesh(newtonWorld, ???, 0.002, 2);

[Carli]

1.???=number of points (=3*triangles)
2.???=pointer to first point (array[0..count-1][0..2] of single)
3.???=stride (=sizeof(array[0..2] of single))

[Kjow]

And how can I extract these info from a GLFreeForm?

Thank you!

[Stucuk]

1.???=number of points (=3*triangles)

Not everyone will be using triangles. Its just a cloud of points. So you can't say its 3*triangles as i could pass 6 points which would create a valid convex hull but would not create any triangle/polygon.

3.???=stride (=sizeof(array[0..2] of single))

Thats only correct if he is only passing the actual vertex's. If his vertex structure has additional information then that would be wrong.

And how can I extract these info from a GLFreeForm?

That would be best asked on the GLScene forum as most here are not going to be using it.

[Carli]

Not everyone will be using triangles.

...
Thats only correct if he is only passing the actual vertex's.

but i saw that he is not very familar with 3d etc. (espeacially when he asks GLScene questions in a Newton-Forum) so i told him only those things he would need to get that one example running.

For a more general usage, i would have said to him "click on NewtonCreateConvexHull and read the wiki"

[Kjow]

Thank you both.
I asked about GLScene here, because the topic is "Lazarus + GLScene", so I wished for help from people that could help me on this platform.

The wiki is not very friendly, especially for ObjectPascal users, and there isn't a tutorial that starts from 0% and arrives to 100% of knowledge. Nowhere I found an example or tutorial that tell me that I need some dll calls instead of others... all I know is from tests and sparse Bits and some help...

I opened a thread called "Lazarus + GLScene" because in the GLScene community Newton is not so much used (there is ODE component, but I hope there will be soon a Newton component also), so I don't think that ask about GLScene usage WITH Newton is a so strange thing.

However, if there isn't anyone that know GLScene, I'll limit myself to ask here things strictly relevant to Newton.

So, to add a dynamic object, do I need the NewtonCreateConvexHull call? (and not NewtonCreateConvexHullFromMesh)

Can anyone adapt this code to make this object dynamic?

Code: Select all

GLFreeForm.LoadFromFile(ExtractFilePath(Application.ExeName)+'mesh.obj');

  xT:= 1;
  yT:= 1;
  zT:= 1;
  massT:=0.001;

  IxxT := massT * (1/12) * (yT*yT+zT*zT);
  IyyT := massT * (1/12) * (xT*xT+zT*zT);
  IzzT := massT * (1/12) * (xT*xT+yT*yT);

  static:= NewtonCreateTreeCollision(Newtonworld, 0);
  NewtonTreeCollisionBeginBuild(static);

  test:= TAffineVectorList.create;
  test:= GLFreeForm.MeshObjects.Items[0].ExtractTriangles;

  for i:= 0 to test.Count div 3 do
  begin
    v[0]:= test[i*3 + 0];
    v[1]:= test[i*3 + 1];
    v[2]:= test[i*3 + 2];
    NewtonTreeCollisionAddFace(static, 3, @v[0], 12, 1);
  end;

  NewtonTreeCollisionEndBuild(static, 1); // with optimization

  NewtonBodyStaticMesh := NewtonCreateBody(Newtonworld, static);

  NewtonBodySetMassMatrix(NewtonBodyStaticMesh, massT, IxxT, IyyT, IzzT);
  Newtonbodysetmatrix(NewtonBodyStaticMesh,NewtonImport.PFloat(GLFreeForm.AbsoluteMatrixAsAddress));

  NewtonbodysetUserdata(NewtonBodyStaticMesh,GLFreeForm);
  GLFreeForm.TagObject := TObject(NewtonBodyStaticMesh);

  NewtonBodySetForceAndTorqueCallBack(NewtonBodyStaticMesh, @ForceAndTorqueCallBack);

  test.Free;     

Thank you very much for patience.