Porting Box2d Lite to AGS Script

[eri0o]

Following the new pointers in managed structs PR, from CW, I decided to give a shot at something that uses lots of pointers just to see what would happen.

So, from the original box2d lite code, from the original erin catto presentation, I attempted a port to AGS Script, just to see what would happen.



b2dlite.ash

Spoiler

Code: ags

// new module header
#define FLT_MAX 340282346638528859811704183484516925440.0
#define MAX_POINTS 32
#define MAX_ARBITERS 16
#define MAX_BODIES 256
#define MAX_JOINTS 256
#define MAX_CONTACTS 2

managed struct Vec2
{
	float x, y;

  import static Vec2* New(float x, float y); // $AUTOCOMPLETESTATICONLY$
 	import void Set(float x, float y);
  import void SetV(Vec2* v);
  import Vec2* Abs();
  import Vec2* Negate();
	import Vec2* Minus(Vec2* vb);
  import Vec2* Plus(Vec2* vb);
  import Vec2* Scale(float a);
  import float Length();
  import float Dot(Vec2* b);
  import float Cross(Vec2* b);
};

managed struct Mat22
{
  float col1_x, col1_y, col2_x, col2_y;
  
  import static Mat22* New(float col1_x, float col1_y, float col2_x, float col2_y); // $AUTOCOMPLETESTATICONLY$
  import static Mat22* NewFromAngle(float angle); // $AUTOCOMPLETESTATICONLY$
  import static Mat22* NewFromVec2(Vec2* col1, Vec2* col2); // $AUTOCOMPLETESTATICONLY$
  import Mat22* Transpose();
  import Mat22* Invert();
  import Mat22* Plus(Mat22* B);
  import Mat22* Multiply(Mat22* B);
  import Mat22* Abs();
};

managed struct Body
{
  import static Body* Create();
	float position_x, position_y;
	float rotation;

	float velocity_x, velocity_y;
	float angularVelocity;

	float force_x, force_y;
	float torque;

	float width_x, width_y;

	float friction;
	float mass, invMass;
	float I, invI;
    
	import void Set(Vec2* w, float m);
	import void AddForce(const Vec2* f);
};

managed struct Joint
{
  import static Joint* Create();
	Mat22* M;
	Vec2* localAnchor1, localAnchor2;
	Vec2* r1, r2;
	Vec2* bias;
	Vec2* P;		// accumulated impulse
	Body* body1;
	Body* body2;
	float biasFactor;
	float softness;
  
	import void Set(Body* body1, Body* body2, Vec2* anchor);

	import void PreStep(float inv_dt);
	import void ApplyImpulse();
};

managed struct FeaturePair
{
  static import FeaturePair* Create();
  
  char inEdge1;
  char outEdge1;
  char inEdge2;
  char outEdge2;
  import attribute int value;
  import int get_value();
  import void set_value(int value);
};

managed struct Contact
{
  static import Contact* Create();
  
	Vec2* position;
	Vec2* normal;
	Vec2* r1, r2;
	float separation;
	float Pn;	// accumulated normal impulse
	float Pt;	// accumulated tangent impulse
	float Pnb;	// accumulated normal impulse for position bias
	float massNormal, massTangent;
	float bias;
	FeaturePair* feature;
  import Contact* CopyTo(Contact* c);
};

managed struct Arbiter
{
  static import Arbiter* Create(Body* b1, Body* b2);
  
  import void Update(Contact* contacts[],  int numContacts);
  
	import void PreStep(float inv_dt);
	import void ApplyImpulse();

	Contact* contacts[];
	int numContacts;

	Body* body1;
	Body* body2;

	// Combined friction
	float friction;
};

managed struct Arbiters
{
  import void Add(Arbiter* arb);
  import void Remove(Body* b1, Body* b2);
  import Arbiter* Get(Body* b1, Body* b2);
  import void Clear();
  
  Arbiter* a[MAX_ARBITERS];
  int a_count;
  import static Arbiters* Create();
};

struct World
{
  import void Init(float gravity_x, float gravity_y, int iterations = 10);
	import void AddBody(Body* body);
	import void AddJoint(Joint* joint);
	import void Clear();

	import void Step(float dt);

	import void BroadPhase();

	Body* bodies[MAX_BODIES];
	int body_count;
  Joint* joints[MAX_JOINTS];
  int joint_count;
	Arbiters* arbiters;
  
	Vec2* gravity;
	int iterations;
	static import attribute bool accumulateImpulses;
  static import bool get_accumulateImpulses();
  static import void set_accumulateImpulses(bool value);
	static import attribute bool warmStarting;
  static import bool get_warmStarting();
  static import void set_warmStarting(bool value);
	static import attribute bool positionCorrection;
  static import bool get_positionCorrection();
  static import void set_positionCorrection(bool value);
};

[close]

b2dlite.asc

Spoiler

Code: ags

// new module script

// assertion check utility
void assert(bool expr)
{
  if (expr == false) AbortGame("Failed assertion!");
}

float _abs(float a)
{
  if (a >= 0.0)
    return a;
  return -a;
}

#region MATH_UTILITIES
static Vec2* Vec2::New(float x, float y) {
  Vec2* v = new Vec2;
  v.x = x;
  v.y = y;
  return v;
}
void  Vec2::Set(float x, float y) { this.x = x;  this.y = y; }
void  Vec2::SetV(Vec2* v) { this.x = v.x;  this.y = v.y; }
Vec2* Vec2::Negate() { return this.New(-this.x, -this.y); }
Vec2* Vec2::Abs() { return this.New(_abs(this.x), _abs(this.y)); }
Vec2* Vec2::Minus(Vec2* v) { return this.New(this.x - v.x, this.y - v.y); }
Vec2* Vec2::Plus(Vec2* v) { return this.New(this.x + v.x, this.y + v.y); }
Vec2* Vec2::Scale(float a) { return this.New(this.x * a, this.y * a); }
float Vec2::Length(){ return Maths.Sqrt(this.x*this.x + this.y*this.y); }
float Vec2::Dot(Vec2* b) { return this.x * b.x + this.y * b.y; }
float Vec2::Cross(Vec2* b){  return this.x * b.y - this.y * b.x; }

static Mat22* Mat22::New(float col1_x, float col1_y, float col2_x, float col2_y)
{
  Mat22* m = new Mat22;
  m.col1_x = col1_x; m.col2_x = col2_x;
  m.col1_y = col1_y; m.col2_y = col2_y;
  return m;
}

static Mat22* Mat22::NewFromAngle(float angle)
{
  float c = Maths.Cos(angle), s = Maths.Sin(angle);
  return Mat22.New(c, s, -s, c);
}
  
static Mat22* Mat22::NewFromVec2(Vec2* col1, Vec2* col2)
{
  return Mat22.New(col1.x, col1.y, col2.x, col2.y);
}

Mat22* Mat22::Transpose() 
{
  return this.New(this.col1_x, this.col2_x, this.col1_y, this.col2_y);
}

Mat22* Mat22::Invert()
{
  float a = this.col1_x, b = this.col2_x, c = this.col1_y, d = this.col2_y;
  float det = a * d - b * c;
  assert(det != 0.0);
  det = 1.0 / det;
  return this.New(det * d, -det * c, -det * b, det * a);
}

Mat22* Mat22::Plus(Mat22* B)
{
  return this.New(this.col1_x + B.col1_x, this.col1_y + B.col1_y, this.col2_x + B.col2_x, this.col2_y + B.col2_y);
}

Mat22* Mat22::Abs()
{
  return this.New(_abs(this.col1_x), _abs(this.col1_y), _abs(this.col2_x), _abs(this.col2_y));
}

Vec2* CrossV2S(Vec2* a, float s)
{
  return Vec2.New(s * a.y, -s * a.x);
}

Vec2* CrossS2V(float s, Vec2* a)
{
  return Vec2.New(-s * a.y, s * a.x);
}

Vec2* MultiplyVec2(Mat22* A, Vec2* v)
{
  return Vec2.New(A.col1_x * v.x + A.col2_x * v.y, A.col1_y * v.x + A.col2_y * v.y);
}

Mat22* Mat22::Multiply(Mat22* matb)
{
   //A * B.col1, A * B.col2);
  float m11 = this.col1_x * matb.col1_x + this.col2_x * matb.col1_y;
  float m12 = this.col1_y * matb.col1_x + this.col2_y * matb.col1_y;
  
  float m21 = this.col1_x * matb.col2_x + this.col2_x * matb.col2_y;
  float m22 = this.col1_y * matb.col2_x + this.col2_y * matb.col2_y;
  return this.New(m11, m12, m21, m22);
}

float _sign(float a)
{
  if(a < 0.0) return -1.0;
  return 1.0;
}

int _maxi(int a, int b)
{
  if (a > b)
    return a;
  return b;
}

int _mini(int a, int b)
{
  if (a < b)
    return a;
  return b;
}

int _clampi(int v, int min, int max)
{
  return _mini(max, _maxi(v, min));
}

float _max(float a, float b)
{
  if (a > b)
    return a;
  return b;
}

float _min(float a, float b)
{
  if (a < b)
    return a;
  return b;
}

float _clamp(float v, float min, float max)
{
  return _min(max, _max(v, min));
}

// Random number in range [-1,1]
float _Random()
{
  float r = IntToFloat(Random(100000));
  r /= 100000.0;
  return 2.0 * r - 1.0;
}

float _RandomRange(float lo, float hi)
{
  float r = IntToFloat(Random(100000));
  r /= 100000.0;
  return (hi - lo) * r + lo;
}
#endregion //MATH_UTILITIES

bool _accumulateImpulses;
bool _warmStarting;
bool _positionCorrection;

static bool World::get_accumulateImpulses()
{
  return _accumulateImpulses;
}

static void World::set_accumulateImpulses(bool value)
{
  _accumulateImpulses = value;
}

static bool World::get_warmStarting()
{
  return _warmStarting;
}

static void World::set_warmStarting(bool value)
{
  _warmStarting = value;
}

static bool World::get_positionCorrection()
{
  return _positionCorrection;
}

static void World::set_positionCorrection(bool value)
{
  _positionCorrection = value;
}

void FeaturePair::set_value(int v)
{
  this.inEdge1 = (v >> 24) & 0xff;
  this.inEdge2 = (v >> 16) & 0xff;
  this.outEdge1 = (v >> 8) & 0xff;
  this.outEdge2 = v & 0xff;
}

int FeaturePair::get_value()
{
  return (this.inEdge1 << 24) & 0xff000000 | (this.inEdge2 << 16) & 0x00ff0000 | (this.outEdge1 << 8) & 0x0000ff00 | this.outEdge2;
}

static FeaturePair* FeaturePair::Create()
{
  FeaturePair* fp = new FeaturePair;
  fp.inEdge1 = 0;
  fp.inEdge2 = 0;
  fp.outEdge1 = 0;
  fp.outEdge2 = 0;
  return fp;
}

void World::AddBody(Body* body)
{
  this.bodies[this.body_count] = body;
  this.body_count++;
}

void World::AddJoint(Joint* joint)
{
  this.joints[this.joint_count] = joint;
  this.joint_count++;
}


void Arbiters::Add(Arbiter* arb)
{
  if(this.a_count < MAX_ARBITERS) {
    this.a[this.a_count] = arb;
    this.a_count++;
  }
}

Contact* Contact::CopyTo(Contact* c)
{
  c.bias = this.bias;
  if(c.feature == null) {
    c.feature = FeaturePair.Create();
  }
  
  c.feature.inEdge1 = this.feature.inEdge1;
  c.feature.inEdge2 = this.feature.inEdge2;
  c.feature.outEdge1 = this.feature.outEdge1;
  c.feature.outEdge2 = this.feature.outEdge2;
  
  c.massNormal = this.massNormal;
  c.massTangent = this.massTangent;
  if(c.normal == null) {
    c.normal = Vec2.New(this.normal.x, this.normal.y);
  } else {
    c.normal.Set(this.normal.x, this.normal.y);  
  }
  
  c.Pn = this.Pn;
  c.Pnb = this.Pnb;
  if(c.position == null) {
    c.position = Vec2.New(c.position.x, c.position.y);
  } else {
    c.position.Set(c.position.x, c.position.y);
  }
  c.Pt = this.Pt;
  if(c.r1 == null) {
    c.r1 = Vec2.New(this.r1.x, this.r1.y);
  } else {
    c.r1.Set(this.r1.x, this.r1.y);
  }
  if(c.r2 == null) {
    c.r2 = Vec2.New(this.r2.x, this.r2.y);
  } else {
    c.r2.Set(this.r2.x, this.r2.y);
  }
  c.separation = this.separation;
  return c;
}

void Arbiters::Remove(Body* b1, Body* b2)
{
  int j=0;
  int removed = 0;
  for(int i=0; i<this.a_count; i++)
  {
    if(this.a[i].body1 == b1 && this.a[i].body2 == b2 ||
       this.a[i].body1 == b2 && this.a[i].body2 == b1 ) {
      removed++;
      continue;
    }
    this.a[j]= this.a[i];
    j++;
  }
  this.a_count-=removed;
}

Arbiter* Arbiters::Get(Body* b1, Body* b2)
{
  for(int i=0; i<this.a_count; i++)
  {
    if(this.a[i].body1 == b1 && this.a[i].body2 == b2 || 
       this.a[i].body1 == b2 && this.a[i].body2 == b1 ) {
      return this.a[i];
    }
  }
  return null;  
}

void Arbiters::Clear()
{
  for(int i=0; i<this.a_count; i++)
  {
    this.a[i] = null;
  }
  this.a_count = 0;
}

static Arbiters* Arbiters::Create()
{
  Arbiters* a = new Arbiters;
  return a;  
}

void World::Clear()
{
  for(int i=0; i<this.body_count; i++)
  {
    this.bodies[i] = null;
  }
  this.body_count = 0;
  
  for(int i=0; i<this.joint_count; i++)
  {
    this.joints[i] = null;
  }
  this.joint_count = 0;
  if(this.arbiters != null) {
    this.arbiters.Clear();
  } else {
    this.arbiters = Arbiters.Create();
  }
}

static Body* Body::Create()
{
  Body* b = new Body;
  b.position_x = 0.0;
  b.position_y = 0.0;
  b.rotation = 0.0;
  b.velocity_x = 0.0;
  b.velocity_y = 0.0;
  b.angularVelocity = 0.0;
  b.force_x = 0.0;
  b.force_y = 0.0;
  b.torque = 0.0;
  b.friction = 0.2;
  
  b.width_x = 1.0;
  b.width_y = 1.0;
  b.mass = FLT_MAX;
  b.invMass = 0.0;
  b.I = FLT_MAX;
  b.invI = 0.0;
  
  return b;
}

void Body::Set(Vec2* w, float m)
{
  this.position_x = 0.0;
  this.position_y = 0.0;
  this.rotation = 0.0;
  this.velocity_x = 0.0;
  this.velocity_y = 0.0;
  this.angularVelocity = 0.0;
  this.force_x = 0.0;
  this.force_y = 0.0;
  this.torque = 0.0;
  this.friction = 0.2;
  
  this.width_x = w.x;
  this.width_y = w.y;
  this.mass = m;

  if (this.mass < FLT_MAX)
  {
    this.invMass = 1.0 / this.mass;
    this.I = this.mass * (this.width_x * this.width_x + this.width_y * this.width_y) / 12.0;
    this.invI = 1.0 / this.I;
  }
  else
  {
    this.invMass = 0.0;
    this.I = FLT_MAX;
    this.invI = 0.0;
  }
}

static Joint* Joint::Create()
{
  Joint* jo = new Joint;
  jo.body1 = null;
  jo.body2 = null;
  
  jo.P = Vec2.New(0.0, 0.0);
  jo.biasFactor = 0.2;
  jo.softness = 0.0;
  
  jo.M = Mat22.New(0.0, 0.0, 0.0, 0.0);
  jo.r1 = Vec2.New(0.0, 0.0);
  jo.r2 = Vec2.New(0.0, 0.0);
  jo.localAnchor1 = Vec2.New(0.0, 0.0);
  jo.localAnchor2 = Vec2.New(0.0, 0.0);
  jo.bias = Vec2.New(0.0, 0.0);
  
  return jo;
}

void Joint::Set(Body* b1, Body* b2, Vec2* anchor)
{
  this.body1 = b1;
  this.body2 = b2;

  Mat22* Rot1 = Mat22.NewFromAngle(this.body1.rotation);
  Mat22* Rot2 = Mat22.NewFromAngle(this.body2.rotation);
  Mat22* Rot1T = Rot1.Transpose();
  Mat22* Rot2T = Rot2.Transpose();

  this.localAnchor1 = MultiplyVec2(Rot1T, anchor.Minus(Vec2.New(this.body1.position_x, this.body1.position_y)));
  this.localAnchor2 = MultiplyVec2(Rot2T, anchor.Minus(Vec2.New(this.body2.position_x, this.body2.position_y)));

  if(this.P == null) {
    this.P = Vec2.New(0.0, 0.0);
  } else {
    this.P.Set(0.0, 0.0);
  }

  this.softness = 0.0;
  this.biasFactor = 0.2;
}

void Joint::PreStep(float inv_dt)
{
  // Pre-compute anchors, mass matrix, and bias.
  Mat22* Rot1 = Mat22.NewFromAngle(this.body1.rotation);
  Mat22* Rot2 = Mat22.NewFromAngle(this.body2.rotation);

  this.r1 = MultiplyVec2(Rot1, this.localAnchor1);
  this.r2 = MultiplyVec2(Rot2, this.localAnchor2);

  // deltaV = deltaV0 + K * impulse
  // invM = [(1/m1 + 1/m2) * eye(2) - skew(r1) * invI1 * skew(r1) - skew(r2) * invI2 * skew(r2)]
  //      = [1/m1+1/m2     0    ] + invI1 * [r1.y*r1.y -r1.x*r1.y] + invI2 * [r1.y*r1.y -r1.x*r1.y]
  //        [    0     1/m1+1/m2]           [-r1.x*r1.y r1.x*r1.x]           [-r1.x*r1.y r1.x*r1.x]
  Mat22* K1 = Mat22.New(
    this.body1.invMass + this.body2.invMass, 0.0,
    0.0, this.body1.invMass + this.body2.invMass);

  Mat22* K2 = Mat22.New( this.body1.invI * this.r1.y * this.r1.y, -this.body1.invI * this.r1.x * this.r1.y, 
                        -this.body1.invI * this.r1.x * this.r1.y,  this.body1.invI * this.r1.x * this.r1.x);
  
  
  Mat22* K3 = Mat22.New(this.body2.invI * this.r2.y * this.r2.y, -this.body2.invI * this.r2.x * this.r2.y,
                       -this.body2.invI * this.r2.x * this.r2.y,   this.body2.invI * this.r2.x * this.r2.x);

  Mat22* K = K1.Plus(K2);
  K = K.Plus(K3);

  K.col1_x += this.softness;
  K.col1_y += this.softness;

  this.M = K.Invert();

  Vec2* p1 = this.r1.Plus(Vec2.New(this.body1.position_x, this.body1.position_y));
  Vec2* p2 = this.r2.Plus(Vec2.New(this.body2.position_x, this.body2.position_y));
  Vec2* dp = p2.Minus(p1);
   
  if (_positionCorrection)
  {
    this.bias = dp.Scale(- this.biasFactor * inv_dt);
  }
  else
  {
    if(this.bias == null) {
      this.bias = Vec2.New(0.0, 0.0);
    } else {
      this.bias.Set(0.0, 0.0);
    }
  }

  if (_warmStarting)
  {
    // Apply accumulated impulse.
    this.body1.velocity_x -= this.body1.invMass * this.P.x;
    this.body1.velocity_y -= this.body1.invMass * this.P.y;
    this.body1.angularVelocity -= this.body1.invI * this.r1.Cross(this.P);
    
    this.body2.velocity_x += this.body2.invMass * this.P.x;
    this.body2.velocity_y += this.body2.invMass * this.P.y;
    this.body2.angularVelocity += this.body2.invI * this.r2.Cross(this.P);
  }
  else
  {
    if(this.P == null) {
      this.P = Vec2.New(0.0, 0.0);
    } else {
      this.P.Set(0.0, 0.0);
    }
  }
}

void Joint::ApplyImpulse()
{
  Vec2* tmpa = CrossS2V(this.body2.angularVelocity, this.r2);
  tmpa.x += this.body2.velocity_x;
  tmpa.y += this.body2.velocity_y;
  tmpa.x -= this.body1.velocity_x;
  tmpa.y -= this.body1.velocity_y;
  
  Vec2* tmpb = CrossS2V(this.body1.angularVelocity, this.r1);
  
  Vec2* dv = tmpa.Minus(tmpb);

  Vec2* tmp = this.bias.Minus(dv);
  tmp = tmp.Minus(this.P.Scale(this.softness));
  Vec2* impulse = MultiplyVec2(this.M, tmp);

  this.body1.velocity_x -= this.body1.invMass*impulse.x;
  this.body1.velocity_y -= this.body1.invMass*impulse.y;
  this.body1.angularVelocity -= this.body1.invI * this.r1.Cross(impulse);
  
  
  this.body2.velocity_x += this.body2.invMass*impulse.x;
  this.body2.velocity_y += this.body2.invMass*impulse.y;
  this.body2.angularVelocity += this.body2.invI * this.r2.Cross(impulse);

  this.P = this.P.Plus(impulse);
}

// Box vertex and edge numbering:
//
//        ^ y
//        |
//        e1
//   v2 ------ v1
//    |        |
// e2 |        | e4  --> x
//    |        |
//   v3 ------ v4
//        e3


enum Axis
{
  FACE_A_X,
  FACE_A_Y,
  FACE_B_X,
  FACE_B_Y
};

enum EdgeNumbers
{
  NO_EDGE = 0,
  EDGE1,
  EDGE2,
  EDGE3,
  EDGE4
};

managed struct ClipVertex
{
  static import ClipVertex* Create();

  Vec2* v;
  FeaturePair* fp;
};


static ClipVertex* ClipVertex::Create()
{
  ClipVertex* cv = new ClipVertex;
  cv.v = Vec2.New(0.0, 0.0);
  cv.fp = FeaturePair.Create();
  return cv;
}

static Contact* Contact::Create()
{
  Contact* c = new Contact;
  c.bias = 0.0;
  c.feature = FeaturePair.Create();
  c.massNormal = 0.0;
  c.massTangent = 0.0;
  c.normal = Vec2.New(0.0, 0.0);
  c.Pn = 0.0;
  c.Pnb = 0.0;
  c.position = Vec2.New(0.0, 0.0);
  c.Pt = 0.0;
  c.r1 = Vec2.New(0.0, 0.0);
  c.r2 = Vec2.New(0.0, 0.0);
  c.separation = 0.0;
  return c;
}

void Flip(FeaturePair* fp)
{
  char tmp = fp.inEdge1;
  fp.inEdge1 = fp.inEdge2;
  fp.inEdge2 = tmp;
  
  tmp = fp.outEdge1; 
  fp.outEdge1 = fp.outEdge2;
  fp.outEdge2 = tmp;
}

int ClipSegmentToLine(ClipVertex* vOut[], ClipVertex* vIn[], Vec2* normal, float offset, char clipEdge)
{
  // Start with no output points
  int numOut = 0;

  // Calculate the distance of end points to the line
  float distance0 = normal.Dot(vIn[0].v) - offset;
  float distance1 = normal.Dot(vIn[1].v) - offset;

  // If the points are behind the plane
  if (distance0 <= 0.0) {
    vOut[numOut] = vIn[0];
    numOut++;
  }
  if (distance1 <= 0.0) {
    vOut[numOut] = vIn[1];
    numOut++;
  }

  // If the points are on different sides of the plane
  if (distance0 * distance1 < 0.0)
  {
    // Find intersection point of edge and plane
    float interp = distance0 / (distance0 - distance1);
    Vec2* tmp_v = vIn[1].v.Minus(vIn[0].v);
    tmp_v = tmp_v.Scale(interp);
    vOut[numOut].v = vIn[0].v.Plus(tmp_v);
    
    if (distance0 > 0.0)
    {
      vOut[numOut].fp = vIn[0].fp;
      vOut[numOut].fp.inEdge1 = clipEdge;
      vOut[numOut].fp.inEdge2 = NO_EDGE;
    }
    else
    {
      vOut[numOut].fp = vIn[1].fp;
      vOut[numOut].fp.outEdge1 = clipEdge;
      vOut[numOut].fp.outEdge2 = NO_EDGE;
    }
    numOut++;
  }

  return numOut;
}

void ComputeIncidentEdge(ClipVertex* c[], Vec2* h, Vec2* pos, Mat22* Rot, Vec2* normal)
{
  // The normal is from the reference box. Convert it
  // to the incident boxe's frame and flip sign.
  Mat22* RotT = Rot.Transpose();
  Vec2* n = MultiplyVec2(RotT, normal);
  n = n.Negate();
  Vec2* nAbs = n.Abs();

  if (nAbs.x > nAbs.y)
  {
    if (_sign(n.x) > 0.0)
    {
      c[0].v.Set(h.x, -h.y);
      c[0].fp.inEdge2 = EDGE3;
      c[0].fp.outEdge2 = EDGE4;

      c[1].v.Set(h.x, h.y);
      c[1].fp.inEdge2 = EDGE4;
      c[1].fp.outEdge2 = EDGE1;
    }
    else
    {
      c[0].v.Set(-h.x, h.y);
      c[0].fp.inEdge2 = EDGE1;
      c[0].fp.outEdge2 = EDGE2;

      c[1].v.Set(-h.x, -h.y);
      c[1].fp.inEdge2 = EDGE2;
      c[1].fp.outEdge2 = EDGE3;
    }
  }
  else
  {
    if (_sign(n.y) > 0.0)
    {
      c[0].v.Set(h.x, h.y);
      c[0].fp.inEdge2 = EDGE4;
      c[0].fp.outEdge2 = EDGE1;

      c[1].v.Set(-h.x, h.y);
      c[1].fp.inEdge2 = EDGE1;
      c[1].fp.outEdge2 = EDGE2;
    }
    else
    {
      c[0].v.Set(-h.x, -h.y);
      c[0].fp.inEdge2 = EDGE2;
      c[0].fp.outEdge2 = EDGE3;

      c[1].v.Set(h.x, -h.y);
      c[1].fp.inEdge2 = EDGE3;
      c[1].fp.outEdge2 = EDGE4;
    }
  }

  c[0].v = pos.Plus(MultiplyVec2(Rot, c[0].v));
  c[1].v = pos.Plus(MultiplyVec2(Rot, c[1].v));
}

// The normal points from A to B
int Collide(Contact* contacts[], Body* bodyA, Body* bodyB)
{
  // Setup
  Vec2* hA = Vec2.New(bodyA.width_x, bodyA.width_y);
  hA = hA.Scale(0.5);
  Vec2* hB = Vec2.New(bodyB.width_x, bodyB.width_y);
  hB = hB.Scale(0.5);

  Vec2* posA = Vec2.New(bodyA.position_x, bodyA.position_y);
  Vec2* posB = Vec2.New(bodyB.position_x, bodyB.position_y);

  Mat22* RotA = Mat22.NewFromAngle(bodyA.rotation);
  Mat22* RotB = Mat22.NewFromAngle(bodyB.rotation);
  
  Mat22* RotAT = RotA.Transpose();
  Mat22* RotBT = RotB.Transpose();

  Vec2* dp = posB.Minus(posA);
  Vec2* dA = MultiplyVec2(RotAT, dp);
  Vec2* dB = MultiplyVec2(RotBT, dp);

  Mat22* C = RotAT.Multiply(RotB);
  Mat22* absC = C.Abs();
  Mat22* absCT = absC.Transpose();

  // Box A faces - Vec2 faceA = Abs(dA) - hA - absC * hB;
  Vec2* faceA = dA.Abs();
  faceA = faceA.Minus(hA);
  faceA = faceA.Minus(MultiplyVec2(absC, hB));
  
  if (faceA.x > 0.0 || faceA.y > 0.0)
    return 0;

  // Box B faces - Vec2 faceB = Abs(dB) - hB - absCT * hA;
  Vec2* faceB = dB.Abs();
  faceB = faceB.Minus(hB);
  faceB = faceB.Minus(MultiplyVec2(absCT, hA));
  
  if (faceB.x > 0.0 || faceB.y > 0.0)
    return 0;

  // Find best axis
  Axis axis;
  float separation;
  Vec2* normal;

  // Box A faces
  axis = FACE_A_X;
  separation = faceA.x;
  if(dA.x > 0.0) {
    normal = Vec2.New(RotA.col1_x, RotA.col1_y);
  } else {
    normal = Vec2.New(-RotA.col1_x, -RotA.col1_y);
  }
  
  float relativeTol = 0.95;
  float absoluteTol = 0.01;

  if (faceA.y > relativeTol * separation + absoluteTol * hA.y)
  {
    axis = FACE_A_Y;
    separation = faceA.y;
    if(dA.y > 0.0) {
      normal.Set(RotA.col2_x, RotA.col2_y);
    } else {
      normal.Set(-RotA.col2_x, -RotA.col2_y);
    }
  }

  // Box B faces
  if (faceB.x > relativeTol * separation + absoluteTol * hB.x)
  {
    axis = FACE_B_X;
    separation = faceB.x;
    if(dB.x > 0.0) {
      normal.Set(RotB.col1_x, RotB.col1_y);
    } else {
      normal.Set(-RotB.col1_x, -RotB.col1_y);
    }
  }

  if (faceB.y > relativeTol * separation + absoluteTol * hB.y)
  {
    axis = FACE_B_Y;
    separation = faceB.y;
    if(dB.y > 0.0) {
      normal.Set(RotB.col2_x, RotB.col2_y);
    } else {
      normal.Set(-RotB.col2_x, -RotB.col2_y);
    }
  }

  // Setup clipping plane data based on the separating axis
  Vec2* frontNormal;
  Vec2* sideNormal;
  ClipVertex* incidentEdge[] = new ClipVertex[2];
  incidentEdge[0] = ClipVertex.Create();
  incidentEdge[1] = ClipVertex.Create();
  float front, negSide, posSide;
  char negEdge, posEdge;

  // Compute the clipping lines and the line segment to be clipped.
  switch (axis)
  {
  case FACE_A_X:
    {
      frontNormal = normal;
      front = posA.Dot(frontNormal) + hA.x;
      sideNormal = Vec2.New(RotA.col2_x, RotA.col2_y);
      float side = posA.Dot(sideNormal);
      negSide = -side + hA.y;
      posSide =  side + hA.y;
      negEdge = EDGE3;
      posEdge = EDGE1;
      ComputeIncidentEdge(incidentEdge, hB, posB, RotB, frontNormal);
    }
    break;

  case FACE_A_Y:
    {
      frontNormal = normal;
      front = posA.Dot(frontNormal) + hA.y;
      sideNormal = Vec2.New(RotA.col1_x, RotA.col1_y);
      float side = posA.Dot(sideNormal);
      negSide = -side + hA.x;
      posSide =  side + hA.x;
      negEdge = EDGE2;
      posEdge = EDGE4;
      ComputeIncidentEdge(incidentEdge, hB, posB, RotB, frontNormal);
    }
    break;

  case FACE_B_X:
    {
      frontNormal = normal.Negate();
      front = posB.Dot(frontNormal) + hB.x;
      sideNormal = Vec2.New(RotB.col2_x, RotB.col2_y);
      float side = posB.Dot(sideNormal);
      negSide = -side + hB.y;
      posSide =  side + hB.y;
      negEdge = EDGE3;
      posEdge = EDGE1;
      ComputeIncidentEdge(incidentEdge, hA, posA, RotA, frontNormal);
    }
    break;

  case FACE_B_Y:
    {
      frontNormal = normal.Negate();
      front = posB.Dot(frontNormal) + hB.y;
      sideNormal = Vec2.New(RotB.col1_x, RotB.col1_y);
      float side = posB.Dot(sideNormal);
      negSide = -side + hB.x;
      posSide =  side + hB.x;
      negEdge = EDGE2;
      posEdge = EDGE4;
      ComputeIncidentEdge(incidentEdge, hA, posA, RotA, frontNormal);
    }
    break;
  }

  // clip other face with 5 box planes (1 face plane, 4 edge planes)

  ClipVertex* clipPoints1[] = new ClipVertex[2];
  clipPoints1[0] = ClipVertex.Create();
  clipPoints1[1] = ClipVertex.Create();
  ClipVertex* clipPoints2[] = new ClipVertex[2];
  clipPoints2[0] = ClipVertex.Create();
  clipPoints2[1] = ClipVertex.Create();
  int np;

  // Clip to box side 1
  np = ClipSegmentToLine(clipPoints1, incidentEdge, sideNormal.Negate(), negSide, negEdge);

  if (np < 2)
    return 0;

  // Clip to negative box side 1
  np = ClipSegmentToLine(clipPoints2, clipPoints1,  sideNormal, posSide, posEdge);

  if (np < 2)
    return 0;

  // Now clipPoints2 contains the clipping points.
  // Due to roundoff, it is possible that clipping removes all points.

  int numContacts = 0;
  for (int i = 0; i < 2; i++)
  {
    float sep = frontNormal.Dot(clipPoints2[i].v) - front;

    if (sep <= 0.0)
    {
      contacts[numContacts].separation = sep;
      contacts[numContacts].normal = normal;
      // slide contact point onto reference face (easy to cull)
      contacts[numContacts].position.SetV(clipPoints2[i].v.Minus(frontNormal.Scale(sep)));
      contacts[numContacts].feature = clipPoints2[i].fp;
      if (axis == FACE_B_X || axis == FACE_B_Y)
        Flip(contacts[numContacts].feature);

      numContacts++;
    }
  }

  return numContacts;
}


static Arbiter* Arbiter::Create(Body* b1, Body* b2)
{
  Arbiter* a = new Arbiter;
 
  if(b1.mass < FLT_MAX) {
  a.body1 = b1;
  a.body2 = b2;
  } else {
  a.body1 = b2;
  a.body2 = b1;
  }
  
  a.contacts = new Contact[MAX_CONTACTS];
  for(int i=0; i<MAX_CONTACTS; i++) {
    a.contacts[i] = Contact.Create();
  }

  a.numContacts = Collide(a.contacts, a.body1, a.body2);

  a.friction = Maths.Sqrt(a.body1.friction * a.body2.friction);
  return a;
}

void Arbiter::Update(Contact* newContacts[], int numNewContacts)
{
  Contact* mergedContacts[2];
  mergedContacts[0] = Contact.Create();
  mergedContacts[1] = Contact.Create();

  for (int i=0; i < numNewContacts; i++)
  {
    Contact* cNew = newContacts[i];
    int k = -1;
    for (int j=0; j < this.numContacts; j++)
    {
      Contact* cOld = this.contacts[j];
      if (cNew.feature.inEdge1 == cOld.feature.inEdge1 &&
          cNew.feature.inEdge2 == cOld.feature.inEdge2 &&
          cNew.feature.outEdge1 == cOld.feature.outEdge1 &&
          cNew.feature.outEdge2 == cOld.feature.outEdge2 )
      {
        k = j;
        break;
      }
    }

    if (k > -1)
    {
      Contact* cOld = this.contacts[k];
      mergedContacts[i] = cNew;
      if (_warmStarting)
      {
        cNew.Pn = cOld.Pn;
        cNew.Pt = cOld.Pt;
        cNew.Pnb = cOld.Pnb;
      }
      else
      {
        cNew.Pn = 0.0;
        cNew.Pt = 0.0;
        cNew.Pnb = 0.0;
      }
    }
    else
    {
      mergedContacts[i] = newContacts[i];
    }
  }

  for (int i = 0; i < numNewContacts; i++)
    this.contacts[i] = mergedContacts[i];

  this.numContacts = numNewContacts;
}


void Arbiter::ApplyImpulse()
{
  Body* b1 = this.body1;
  Body* b2 = this.body2;

  for (int i=0; i < this.numContacts; i++)
  {
    Contact* c = this.contacts[i];
    c.r1.x = c.position.x - b1.position_x;
    c.r1.y = c.position.y - b1.position_y;
    c.r2.x = c.position.x - b2.position_x;
    c.r2.y = c.position.y - b2.position_y;

    // Relative velocity at contact
    Vec2* tmpa = CrossS2V(b2.angularVelocity, c.r2);
    tmpa.x += b2.velocity_x;
    tmpa.y += b2.velocity_y;
    tmpa.x -= b1.velocity_x;
    tmpa.y -= b1.velocity_y;
    
    Vec2* tmpb = CrossS2V(b1.angularVelocity, c.r1);
    
    Vec2* dv = tmpa.Minus(tmpb);

    // Compute normal impulse
    float vn = dv.Dot(c.normal);

    float dPn = c.massNormal * (-vn + c.bias);

    if (_accumulateImpulses)
    {
      // Clamp the accumulated impulse
      float Pn0 = c.Pn;
      c.Pn = _max(Pn0 + dPn, 0.0);
      dPn = c.Pn - Pn0;
    }
    else
    {
      dPn = _max(dPn, 0.0);
    }

    // Apply contact impulse
    Vec2* Pn = c.normal.Scale(dPn);

    b1.velocity_x -= b1.invMass * Pn.x;
    b1.velocity_y -= b1.invMass * Pn.y;
    b1.angularVelocity -= b1.invI * c.r1.Cross(Pn);

    b2.velocity_x += b2.invMass * Pn.x;
    b2.velocity_y += b2.invMass * Pn.y;
    b2.angularVelocity += b2.invI * c.r2.Cross(Pn);
    
    // Relative velocity at contact
    
    tmpa = CrossS2V(b2.angularVelocity, c.r2);
    tmpa.x += b2.velocity_x;
    tmpa.y += b2.velocity_y;
    tmpa.x -= b1.velocity_x;
    tmpa.y -= b1.velocity_y;
    
    tmpb = CrossS2V(b1.angularVelocity, c.r1);
    
    dv = tmpa.Minus(tmpb);

    Vec2* tangent = CrossV2S(c.normal, 1.0);
    float vt = dv.Dot(tangent);
    float dPt = c.massTangent * (-vt);

    if (_accumulateImpulses)
    {
      // Compute friction impulse
      float maxPt = this.friction * c.Pn;

      // Clamp friction
      float oldTangentImpulse = c.Pt;
      c.Pt = _clamp(oldTangentImpulse + dPt, -maxPt, maxPt);
      dPt = c.Pt - oldTangentImpulse;// _clamp(c.Pt - oldTangentImpulse, -maxPt, maxPt);
    }
    else
    {
      float maxPt = this.friction * dPn;
      dPt = _clamp(dPt, -maxPt, maxPt);
    }

    // Apply contact impulse
    Vec2* Pt = tangent.Scale(dPt);

    b1.velocity_x -= b1.invMass * Pt.x;
    b1.velocity_y -= b1.invMass * Pt.y;
    b1.angularVelocity -= b1.invI * c.r1.Cross(Pt);

    b2.velocity_x += b2.invMass * Pt.x;
    b2.velocity_y += b2.invMass * Pt.y;
    b2.angularVelocity += b2.invI * c.r2.Cross(Pt);
  }
}

void Arbiter::PreStep(float inv_dt)
{
  float k_allowedPenetration = 0.01;
  float k_biasFactor = 0.0;
  if(_positionCorrection) k_biasFactor = 0.2;

  for (int i = 0; i < this.numContacts; i++)
  {
    Contact* c = this.contacts[i];

    Vec2* r1 = new Vec2;
    Vec2* r2 = new Vec2;
    
    r1.x = c.position.x - this.body1.position_x;
    r1.y = c.position.y - this.body1.position_y;
    r2.x = c.position.x - this.body2.position_x;
    r2.y = c.position.y - this.body2.position_y;

    // Precompute normal mass, tangent mass, and bias.
    float rn1 = r1.Dot(c.normal);
    float rn2 = r2.Dot(c.normal);
    float kNormal = this.body1.invMass + this.body2.invMass;
    kNormal += this.body1.invI * (r1.Dot(r1) - rn1 * rn1) + this.body2.invI * (r2.Dot(r2) - rn2 * rn2);
    c.massNormal = 1.0 / kNormal;

    Vec2* tangent = CrossV2S(c.normal, 1.0);
    float rt1 = r1.Dot(tangent);
    float rt2 = r2.Dot(tangent);
    float kTangent = this.body1.invMass + this.body2.invMass;
    kTangent += this.body1.invI * (r1.Dot(r1) - rt1 * rt1) + this.body2.invI * (r2.Dot(r2) - rt2 * rt2);
    c.massTangent = 1.0 /  kTangent;

    c.bias = -k_biasFactor * inv_dt * _min(0.0, c.separation + k_allowedPenetration);

    if (_accumulateImpulses)
    {
      // Apply normal + friction impulse
      Vec2* ppp = tangent.Scale(c.Pt);
      Vec2* pp = c.normal.Scale(c.Pn);
      Vec2* P = pp.Plus(ppp);
      pp = null; ppp = null;

      this.body1.velocity_x -= this.body1.invMass * P.x;
      this.body1.velocity_y -= this.body1.invMass * P.y;      
      this.body1.angularVelocity -= this.body1.invI * r1.Cross(P);

      this.body2.velocity_x += this.body2.invMass * P.x;
      this.body2.velocity_y += this.body2.invMass * P.y;
      this.body2.angularVelocity += this.body2.invI * r2.Cross(P);
    }
  }
}

void World::BroadPhase()
{
  // O(n^2) broad-phase
  for (int i = 0; i < this.body_count; i++)
  {
    Body* bi = this.bodies[i];

    for (int j = i + 1; j < this.body_count; j++)
    {
      Body* bj = this.bodies[j];

      if (bi.invMass == 0.0 && bj.invMass == 0.0)
        continue;

      Arbiter* newArb = Arbiter.Create(bi, bj);

      if (newArb.numContacts > 0)
      {
        Arbiter* arb = this.arbiters.Get(bi, bj);
        if (arb == null)
        {
          this.arbiters.Add(newArb);
        }
        else
        {
          arb.Update(newArb.contacts, newArb.numContacts);
        }
      }
      else
      {
        this.arbiters.Remove(bi, bj);
      }
    }
  }
}

void World::Step(float dt)
{
  float inv_dt = 0.0;
  if(dt > 0.0) {
    inv_dt = 1.0 / dt;
  }

  // Determine overlapping bodies and update contact points.
  this.BroadPhase();

  // Integrate forces.
  for (int i = 0; i < this.body_count; i++)
  {
    Body* b = this.bodies[i];

    if (b.invMass == 0.0)
      continue;

    b.velocity_x += dt * (this.gravity.x + b.invMass * b.force_x);
    b.velocity_y += dt * (this.gravity.y + b.invMass * b.force_y);
    b.angularVelocity += dt * b.invI * b.torque;
  }

  // Perform pre-steps. 
  for (int i=0; i< this.arbiters.a_count; i++)
  {
    Arbiter* arb = this.arbiters.a[i];
    arb.PreStep(inv_dt);
  }

  for (int i = 0; i < this.joint_count; i++)
  {
    this.joints[i].PreStep(inv_dt);
  }

  // Perform iterations
  for (int i=0; i < this.iterations; i++)
  {
    for (int j=0; j< this.arbiters.a_count; j++)
    {
      Arbiter* arb = this.arbiters.a[j];
      arb.ApplyImpulse();
    }

    for (int j=0; j < this.joint_count; j++)
    {
      this.joints[j].ApplyImpulse();
    }
  }

  // Integrate Velocities
  for (int i = 0; i < this.body_count; i++)
  {
    Body* b = this.bodies[i];

    b.position_x += dt * b.velocity_x;
    b.position_y += dt * b.velocity_y;
    b.rotation += dt * b.angularVelocity;

    b.force_x = 0.0;
    b.force_y = 0.0;
    b.torque = 0.0;
  }
}

void World::Init(float gravity_x, float gravity_y, int iterations)
{
  this.Clear();
  this.gravity = Vec2.New(gravity_x, gravity_y);
  this.iterations = iterations;
}
 
void game_start()
{
  _accumulateImpulses = true;
  _warmStarting = true;
  _positionCorrection = true;
}

[close]

Usage, room script example

Code: ags

// room script file
#define MAX_STUFF 32

#define SCALE 16.0

World world;
float step;
struct Thing {
  Body* b;
  Overlay* ovr;
  DynamicSprite* dnspr;
  
  import void InitFromBody(Body* b);
  import void Render();
};
Thing things[MAX_STUFF];
int thing_count;
Overlay* scr_ovr;
DynamicSprite* scr_spr;

void DrawContacts()
{
  if(scr_ovr == null) {
    scr_spr = DynamicSprite.Create(Screen.Width, Screen.Height);
    scr_ovr = Overlay.CreateGraphical(0, 0, scr_spr.Graphic);
    scr_ovr.ZOrder = 1000;
  }
  
  DrawingSurface* surf = scr_spr.GetDrawingSurface();
  surf.Clear(COLOR_TRANSPARENT);
  surf.DrawingColor = 61871;
  
  for(int arsi=0; arsi<world.arbiters.a_count; arsi++) {
    Arbiter* arb = world.arbiters.a[arsi];
    for(int i=0; i<arb.numContacts; i++) {
      int cnx = FloatToInt(arb.contacts[i].position.x*SCALE)+Screen.Width/2;
      int cny = FloatToInt(arb.contacts[i].position.y*SCALE)+Screen.Height/2;
      surf.DrawCircle(cnx, cny, 3);
    }  
  }
}

void Thing::InitFromBody(Body* b) {
  this.b = b;
  
  DrawingSurface* surf;
  int w = FloatToInt(b.width_x*SCALE);
  int h = FloatToInt(b.width_y*SCALE);
  this.dnspr = DynamicSprite.Create(w, h);
  surf = this.dnspr.GetDrawingSurface();
  surf.Clear(256 + Random(65504));
  if(w > 2 && h > 2) {
    surf.DrawingColor = 256 + Random(65504);
    surf.DrawRectangle(1, 1, w-2, h-2);
  }
  surf.Release();
  
  this.ovr = Overlay.CreateGraphical(0, 0, this.dnspr.Graphic);
  this.ovr.X = FloatToInt((this.b.position_x - this.b.width_x/2.0)*SCALE)+Screen.Width/2;
  this.ovr.Y = FloatToInt((this.b.position_y - this.b.width_y/2.0)*SCALE)+Screen.Height/2;
}

void Thing::Render() {
  int w = FloatToInt((this.b.width_x)*SCALE);
  int h = FloatToInt((this.b.width_y)*SCALE);
  this.ovr.Graphic = this.dnspr.Graphic;
  this.ovr.X = FloatToInt((this.b.position_x - this.b.width_x/2.0)*SCALE)+Screen.Width/2;
  this.ovr.Y = FloatToInt((this.b.position_y - this.b.width_y/2.0)*SCALE)+Screen.Height/2;
  this.ovr.Width = w;
  this.ovr.Height = h;
  this.ovr.Rotation = Maths.RadiansToDegrees(this.b.rotation);
}

void NewBody(float x, float y, float width, float height, float mass) {
  Body* b = Body.Create();
  b.Set(Vec2.New(width, height), mass);
  b.position_x = x;
  b.position_y = y;
  
  things[thing_count].InitFromBody(b);
  thing_count++;
	world.AddBody(b);
}

void RenderAll() {
  for(int i=0; i<thing_count; i++) {
    things[i].Render();
  }
  DrawContacts();
}

function room_Load()
{
  world.Init(0.0, 10.0);
  step = 1.0/IntToFloat(GetGameSpeed());
  
  NewBody(0.0, 0.5*20.0, 100.0, 20.0,   FLT_MAX);
  NewBody(0.0,       -4.0,   1.0,  1.0,   200.0);
  NewBody(1.0,       -6.0,   1.0,  1.0,   200.0);
  NewBody(2.0,       -5.0,   1.0,  1.0,   200.0);
  NewBody(1.5,       -2.0,   1.0,  1.0,   800.0);
  NewBody(2.4,       -9.0,   1.0,  1.0,   200.0);
  NewBody(1.4,       -10.0,   1.0,  1.0,   200.0);
  NewBody(2.8,       -12.0,   1.0,  1.0,   200.0);
  NewBody(1.8,       -14.0,   1.0,  1.0,   200.0);
  NewBody(0.8,       -12.0,   1.0,  1.0,   200.0);
}

bool start;
function room_RepExec()
{
  if(!start) {
    Display("START");
    start = !start;
  }
  
  world.Step(step);

  RenderAll();
}

Spoiler

at first it wasn't working...

[close]

It's working!!!

[eri0o]

minor updates above...



Still not working but thought the failure was still fun. I think I am positioning and calculating the contacts wrong in some way, not sure how yet.

[eri0o]

Minor update! Got the interaction between static and dynamic objects working! Now need to figure out what is causing dynamic-dynamic interactions to be occasionally explosive!

Edit: found the error! it's working now, updating the first topic with t he current library. It's going to be a little while until I post the actual more final thing in modules since this is ags4 only.

[Alan v.Drake]

Lookin' good!

- Alan

[eri0o]

I kinda want to figure out a very simple actual game I can use this to add a bit motivation.

Code wise I looked into a few things

• adding circles
• adding rounded rectangles (capsules)
• optimize broadphase
• optimize AGS Script
• simplify API

[Crimson Wizard]

I kinda want to figure out a very simple actual game I can use this to add a bit motivation.

What about a color-match game, but with physics? Colored squares fall from above and player must move them sideways or drop fast. If same-colored squares are close enough and join by sides, they will despawn.

But everything works with physics, so slightest mistake may create a mess.

Option 2:
a cannon shooting a castle made of blocks. Castles may be of different shape, and you only have limited shots.

[eri0o]

Thanks for the ideas CW, I am still thinking about them.


I want to have an actual release as module later but there's a lot to do until then. In the meantime, I just made the repository public, just to have a reference to the code somewhere else beyond the forums.

https://github.com/ericoporto/simple_physics

Maybe even in this bad stage it can be useful for someone. Noted a rough draft of intentions in the README.

[newwaveburritos]

Well, that's amazing!

[eri0o]

I guess now that ags4 has real alpha releases people may actually try this, so if you have trouble or questions please ask and I will try to at some point do an actual release of this as a module too!