bero1985/kraft

Kraft Physics Engine is an open source Object Pascal physics engine library that can be used in 3D games.

kraft's Issues

TKraftShapeBox creates boxes with doubled sizes

Hello,
i am trying to get into the kraft physics engine and try to create some basic examples to be shared to the public ( https://github.com/PascalCorpsman/kraft_examples )

Doing this i found a behavior i did not expect.

When creating a TKraftShapeBox with the following command:

Shape := TKraftShapeBox.Create(KraftWorld, RigidBody, vector3(2, 1 2));

I expect to get a box with dimensions (2 / 1 / 2) but instead i get a box with dimensions (4 / 2 / 4)

To fix this i need to create the box with

Shape := TKraftShapeBox.Create(KraftWorld, RigidBody, vector3(2 / 2, 1 / 2, 2 / 2));

So is this a bug or is my english "bad" in the way of understanding "AExtents"

Broken Link in Readme.md

The Link http://box2d.org/files/GDC2015/DirkGregorius_Contacts.pdf seems to be brocken, i get a 404 message.

bug in raycast vehicle demo

TKraftConstraintJointGrab: Need to SetToAwake() RigidBody after change SetWorldPoint()

Hi,
After creating TKraftConstraintJointGrab and changing world point by SetWorldPoint() I need to add SetToAwake() to body start moving. Is it a bug or design decision ?

Use with Firemonkey

Is it possible to use this lib with Firemonkey please?
Thank you

Centre of Mass not working with compound objects ..

Dear Benjamin,

i created this example: https://github.com/PascalCorpsman/kraft_examples/tree/main/001_Compound which creates a rigid body containing two "simple" shapes. Than i adjusted the center of mass and let it fall down on the floor. As soon the object touches the ground it completly freaks out and is shoot "away". If you look carefully you can see that it is rotation around the correct CG. But i expect it not to behave like this (i think it should fall down and then fall over to the side).
As following i post the important code parts:

Procedure TForm1.CreateWorld;
Var
  RigidBody: TKraftRigidBody;
  Shape: TKraftShape;
  Floor: TKraftRigidBody;
  FloorShape: TKraftShapePlane; // A Plane infinite in width
Begin
  (*
   * Each element in the Physiks Engine is a TKraftRigidBody
   * it can consists of multiple shapes.
   * A Shape is a container vor a hull and connects the Body with the hull ?
   *)
  // 1. Floor Creation
  Floor := TKraftRigidBody.Create(KraftWorld);
  Floor.SetRigidBodyType(krbtSTATIC);
  // Planes are defined by their normal vector and distance to the Origin.
  FloorShape := TKraftShapePlane.Create(KraftWorld, Floor, Plane(Vector3Norm(Vector3(0.0, 1.0, 0.0)), 0.0));
  FloorShape.Restitution := 0.3; // TODO: Why, it is static ?
  FloorShape.Density := 1.0; // TODO: Why, it is static ?
  Floor.ForcedMass := 0.01; // TODO: Why, it is static ?
  Floor.Finish;
  // Move the Floor plane to the Needed position ;)
  Floor.SetWorldTransformation(Matrix4x4Translate(0.0, 0.0, 0.0));
  (*
   * Create a box consisting of to convex hulls
   *)
  RigidBody := TKraftRigidBody.Create(KraftWorld);
  RigidBody.SetRigidBodyType(krbtSTATIC); // Init as static Object
  (*
   * Lets form a ****
   *                *
   *                *
   *                *
   *                * structure
   *)
  shape := TKraftShapeBox.Create(KraftWorld, RigidBody, Vector3(0.5, 2, 0.5));
  Shape.Restitution := 0.3;
  Shape.Density := 1.0;
  Shape.LocalTransform := Matrix4x4Translate(0, 2, 0);
  Shape.ForcedMass := 1;
  // Shape.SynchronizeTransform; -- is this needed ?
  Shape.Finish;
  shape := TKraftShapeBox.Create(KraftWorld, RigidBody, Vector3(2, 0.5, 0.5));
  Shape.Restitution := 0.3;
  Shape.Density := 1.0;
  Shape.LocalTransform := Matrix4x4Translate(1.5, 4.5, 0);
  Shape.ForcedMass := 1;
  // Shape.SynchronizeTransform; -- is this needed ?
  Shape.Finish;
  RigidBody.ForcedMass := 10;
  RigidBody.Finish;
  RigidBody.SetWorldPosition(MoveableBoxStartingPosition);

  CompoundBox := RigidBody;

  // Set the Centre of mass 
  CompoundBox.ForcedCenterOfMass.Vector := Vector3(-ScrollBar1.Position / 50 + 1.5, 2, 0);
  CompoundBox.BodyInertiaTensor := Matrix3x3Identity;
  // Set the Physics Engine to use the given Centre of Mass and do not auto calc it by the shapes !
  CompoundBox.Flags := CompoundBox.Flags + [krbfHasForcedCenterOfMass];
  CompoundBox.Finish; // Update the internal data structures


// and make the Body Moveable
  CompoundBox.SetRigidBodyType(krbtDynamic); // krbtKinematic ??
  CompoundBox.Finish; 

End; 

So the question is, is this a Bug in the engine ? Do i use it wrong ? (and if so how is it done correct ?) Do you need further informations (if so the code of the complete example is linked at the top)

sandbox gtk error

Although I do not think it's a problem with your kraft, I wanted to try the Sandbox in Linux.

MyConf: (He currently compiles all kinds of 3D things, Castle, Zengl, etc..)
Debian11, i3-wm, Laz 2.2, FPC 3.2.2

Error:

[FORMS.PP] ExceptionOccurred 
  Sender=Exception
  Exception=Could not find FB config
  Stack trace:
  $000000000090810D  GTK_GL_AREA_SHARE_NEW_USEFPGLX,  line 643 of glgtkglxcontext.pas
  $000000000090801C  GTK_GL_AREA_SHARE_NEW,  line 598 of glgtkglxcontext.pas
  $0000000000907FCA  GTK_GL_AREA_NEW,  line 575 of glgtkglxcontext.pas
  $00000000009088B3  LOPENGLCREATECONTEXTCORE,  line 890 of glgtkglxcontext.pas
  $0000000000908B71  LOPENGLCREATECONTEXT,  line 939 of glgtkglxcontext.pas
  $00000000008B075E  CREATEHANDLE,  line 724 of openglcontext.pas
  $0000000000641CD5  CREATEWND,  line 7545 of include/wincontrol.inc
  $0000000000641480  CREATEHANDLE,  line 7455 of include/wincontrol.inc
  $0000000000642C28  HANDLENEEDED,  line 7908 of include/wincontrol.inc
  $0000000000641F97  CREATEWND,  line 7590 of include/wincontrol.inc
  $0000000000641480  CREATEHANDLE,  line 7455 of include/wincontrol.inc
  $0000000000642C28  HANDLENEEDED,  line 7908 of include/wincontrol.inc
  $000000000063F609  GETHANDLE,  line 6517 of include/wincontrol.inc
  $000000000089C4A5  ADDPAGE,  line 370 of gtk2pagecontrol.inc
  $00000000007A7898  ADDREMOVEPAGEHANDLE,  line 720 of include/customnotebook.inc
  $00000000007A6647  CREATEWND,  line 286 of include/customnotebook.inc
  $0000000000641480  CREATEHANDLE,  line 7455 of include/wincontrol.inc

Compile but not execute.

Feature Request TKraftShapeCone, TKraftShapeCylinder

Looking at "TKraftShapeType" i am missing Cone and Cylinder.

Are you looking forward to implement these two ?

If not i can / will try to implement them in the way you did TKraftShapeBox using a ConvexHull and then use a Pull Request to share..

Feature request: Constrain position changes to particular axes (for 2D games)

In order to use Kraft for 2D games, I needed two things:

1. constrain rotations to only happen around the Z axis. This is already straightforward using the krbfLockAxis* Flags.
2. constrain translation to only happen along the X and Y axis. I'm right now doing it using a rather hacky method (more info below).

My feature request is to add flags like

krbfLockTranslationX
krbfLockTranslationY
krbfLockTranslationZ

to the TKraftRigidBodyFlag .

Once you constrain the rotations and positions like above, one can use Kraft for 2D games very comfortably :) Demo (where I constrain position using my hacky method below) is on https://www.youtube.com/watch?v=hIuEGnRm-yM , more information on https://castle-engine.sourceforge.io/wp/2017/09/13/castle-game-engine-2d-physics-using-kraft/ . The CGE manual on https://castle-engine.sourceforge.io/manual_physics.php also has a short section "2D games".

Right now, I constrain the position using this code:

    NewPos := Shape.GetCenter(Shape.InterpolatedWorldTransform);
    if LockPosition <> [] then
    begin
      // apply LockPosition to fix some NewPos coords
      if 0 in LockPosition then NewPos.X := Transform.Translation[0];
      if 1 in LockPosition then NewPos.Y := Transform.Translation[1];
      if 2 in LockPosition then NewPos.Z := Transform.Translation[2];
    end;
    Transform.Translation := VectorFromKraft(NewPos);
    if LockPosition <> [] then
      // fix also position at Kraft side after fixing by LockPosition
      Body.SetWorldTransformation(MatrixToKraft(Transform.Transform));

In other words, I implement the LockPosition by taking the position calculated by Kraft, reverting some of it's components (the locked components) to the previous position, and sending the "fixed" position back to Kraft. This actually works very well (as the demo shows), but it feels like a hack, as I'm reading + writing back the object position every frame, instead of "just reading" the position calculated by Kraft.

If Kraft would allow me to do something like

RigidBody.Flags := RigidBody.Flags + [krbfLockTranslationZ]

then the work would be done on the Kraft side, in a more cleaner way I think:)

some slowdown

Hi
in the brick wall demo , if i shot the first ball into the wall , the fps decreases to (1~2) for about 4 seconds , then it increases to 1200 . and thats the only issue i have .

my laptop is duel core 2.2 ghz , with nvidea Quadro gpu