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Merged
merged 1 commit into from
Jun 18, 2025
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[upstream] Tunable joint stiffness (box2d #934) #34

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8 changes: 4 additions & 4 deletions src/Box2D.NET.Samples/SampleApp.cs
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Expand Up @@ -417,7 +417,7 @@ public byte[] AllocFcn(uint size, int alignment)
long sizeAligned = ((size - 1) | (uint)(alignment - 1)) + 1;
B2_ASSERT((sizeAligned & (alignment - 1)) == 0);

// #if defined( _WIN64 ) || defined( _WIN32 )
// #if defined( _MSC_VER ) || defined( __MINGW32__ ) || defined( __MINGW64__ )
// void* ptr = _aligned_malloc( sizeAligned, alignment );
// #else
// void* ptr = aligned_alloc(alignment, sizeAligned);
Expand All @@ -429,7 +429,7 @@ public byte[] AllocFcn(uint size, int alignment)

private void FreeFcn(byte[] mem)
{
// #if defined( _WIN64 ) || defined( _WIN32 )
// #if defined( _MSC_VER ) || defined( __MINGW32__ ) || defined( __MINGW64__ )
// _aligned_free( mem );
// #else
// free(mem);
Expand Down Expand Up @@ -737,8 +737,8 @@ private void UpdateUI()
if (ImGui.BeginTabItem("Controls"))
{
ImGui.PushItemWidth(100.0f);
ImGui.SliderInt("Sub-steps", ref _context.settings.subStepCount, 1, 50);
ImGui.SliderFloat("Hertz", ref _context.settings.hertz, 5.0f, 120.0f, "%.0f hz");
ImGui.SliderInt("Sub-steps", ref _context.settings.subStepCount, 1, 32);
ImGui.SliderFloat("Hertz", ref _context.settings.hertz, 5.0f, 240.0f, "%.0f hz");

if (ImGui.SliderInt("Workers", ref _context.settings.workerCount, 1, maxWorkers))
{
Expand Down
19 changes: 6 additions & 13 deletions src/Box2D.NET.Samples/Samples/Characters/Mover.cs
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Expand Up @@ -84,7 +84,7 @@
public bool m_jumpReleased;
public bool m_lockCamera;

private int m_deltaX;

Check warning on line 87 in src/Box2D.NET.Samples/Samples/Characters/Mover.cs

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GitHub Actions / test-macos-latest-9 

The field 'Mover.m_deltaX' is never used
private int m_deltaY;

private static Sample Create(SampleContext context)
Expand Down Expand Up @@ -306,7 +306,7 @@
desiredSpeed = m_maxSpeed;
}

float noWalkSteer = 0.0f;

Check warning on line 309 in src/Box2D.NET.Samples/Samples/Characters/Mover.cs

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GitHub Actions / test-ubuntu-latest-8 

The variable 'noWalkSteer' is assigned but its value is never used

Check warning on line 309 in src/Box2D.NET.Samples/Samples/Characters/Mover.cs

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GitHub Actions / test-macos-latest-9 

The variable 'noWalkSteer' is assigned but its value is never used
if (m_onGround)
{
m_velocity.Y = 0.0f;
Expand Down Expand Up @@ -397,13 +397,8 @@
{
float pogoCurrentLength = castResult.fraction * rayLength;

float zeta = m_pogoDampingRatio;
float hertz = m_pogoHertz;
float omega = 2.0f * B2_PI * hertz;
float omegaH = omega * timeStep;

m_pogoVelocity = (m_pogoVelocity - omega * omegaH * (pogoCurrentLength - pogoRestLength)) /
(1.0f + 2.0f * zeta * omegaH + omegaH * omegaH);
float offset = pogoCurrentLength - pogoRestLength;
m_pogoVelocity = b2SpringDamper(m_pogoHertz, m_pogoDampingRatio, offset, m_pogoVelocity, timeStep);

B2Vec2 delta = castResult.fraction * translation;
m_draw.DrawSegment(origin, origin + delta, B2HexColor.b2_colorGray);
Expand Down Expand Up @@ -445,15 +440,13 @@
mover.radius = m_capsule.radius;

b2World_CollideMover(m_worldId, ref mover, collideFilter, PlaneResultFcn, this);
B2PlaneSolverResult solverResult = b2SolvePlanes(target, m_planes, m_planeCount);

m_totalIterations += solverResult.iterationCount;
B2PlaneSolverResult result = b2SolvePlanes(target - m_transform.p, m_planes, m_planeCount);

B2Vec2 moverTranslation = solverResult.position - m_transform.p;
m_totalIterations += result.iterationCount;

float fraction = b2World_CastMover(m_worldId, ref mover, moverTranslation, castFilter);
float fraction = b2World_CastMover(m_worldId, ref mover, result.translation, castFilter);

B2Vec2 delta = fraction * moverTranslation;
B2Vec2 delta = fraction * result.translation;
m_transform.p += delta;

if (b2LengthSquared(delta) < tolerance * tolerance)
Expand Down
8 changes: 4 additions & 4 deletions src/Box2D.NET.Samples/Samples/Determinisms/FallingHinges.cs
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Expand Up @@ -38,7 +38,8 @@ public FallingHinges(SampleContext context) : base(context)
m_camera.m_center = new B2Vec2(0.0f, 7.5f);
m_camera.m_zoom = 10.0f;
}
m_data = CreateFallingHinges( m_worldId );

m_data = CreateFallingHinges(m_worldId);
m_done = false;
}

Expand All @@ -47,9 +48,9 @@ public override void Step()
{
base.Step();

if (m_done == false)
if (m_context.settings.pause == false && m_done == false)
{
m_done = UpdateFallingHinges( m_worldId, ref m_data );
m_done = UpdateFallingHinges(m_worldId, ref m_data);
}
}

Expand All @@ -60,7 +61,6 @@ public override void Draw(Settings settings)
if (m_done)
{
DrawTextLine($"sleep step = {m_data.sleepStep}, hash = 0x{m_data.hash:X8}");

}
}
}
19 changes: 10 additions & 9 deletions src/Box2D.NET.Samples/Samples/Doohickey.cs
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Expand Up @@ -13,17 +13,16 @@ namespace Box2D.NET.Samples.Samples;

public class Doohickey
{
B2BodyId m_wheelId1;
B2BodyId m_wheelId2;
B2BodyId m_barId1;
B2BodyId m_barId2;
private B2BodyId m_wheelId1;
private B2BodyId m_wheelId2;
private B2BodyId m_barId1;
private B2BodyId m_barId2;

B2JointId m_axleId1;
B2JointId m_axleId2;
B2JointId m_sliderId;

bool m_isSpawned;
private B2JointId m_axleId1;
private B2JointId m_axleId2;
private B2JointId m_sliderId;

private bool m_isSpawned;

public Doohickey()
{
Expand All @@ -37,6 +36,8 @@ public void Spawn(B2WorldId worldId, B2Vec2 position, float scale)
bodyDef.type = B2BodyType.b2_dynamicBody;

B2ShapeDef shapeDef = b2DefaultShapeDef();
shapeDef.material.rollingResistance = 0.1f;

B2Circle circle = new B2Circle(new B2Vec2(0.0f, 0.0f), 1.0f * scale);
B2Capsule capsule = new B2Capsule(new B2Vec2(-3.5f * scale, 0.0f), new B2Vec2(3.5f * scale, 0.0f), 0.15f * scale);

Expand Down
13 changes: 10 additions & 3 deletions src/Box2D.NET.Samples/Samples/Joints/BallAndChain.cs
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Expand Up @@ -51,7 +51,8 @@ public BallAndChain(SampleContext context) : base(context)

B2ShapeDef shapeDef = b2DefaultShapeDef();
shapeDef.density = 20.0f;

shapeDef.filter.categoryBits = 0x1;
shapeDef.filter.maskBits = 0x2;
B2RevoluteJointDef jointDef = b2DefaultRevoluteJointDef();

int jointIndex = 0;
Expand All @@ -70,8 +71,10 @@ public BallAndChain(SampleContext context) : base(context)
jointDef.bodyIdB = bodyId;
jointDef.localAnchorA = b2Body_GetLocalPoint(jointDef.bodyIdA, pivot);
jointDef.localAnchorB = b2Body_GetLocalPoint(jointDef.bodyIdB, pivot);
// jointDef.enableMotor = true;
jointDef.enableMotor = true;
jointDef.maxMotorTorque = m_frictionTorque;
jointDef.enableSpring = i > 0;
jointDef.hertz = 4.0f;
m_jointIds[jointIndex++] = b2CreateRevoluteJoint(m_worldId, ref jointDef);

prevBodyId = bodyId;
Expand All @@ -83,8 +86,10 @@ public BallAndChain(SampleContext context) : base(context)
B2BodyDef bodyDef = b2DefaultBodyDef();
bodyDef.type = B2BodyType.b2_dynamicBody;
bodyDef.position = new B2Vec2((1.0f + 2.0f * m_count) * hx + circle.radius - hx, m_count * hx);

B2BodyId bodyId = b2CreateBody(m_worldId, ref bodyDef);

shapeDef.filter.categoryBits = 0x2;
shapeDef.filter.maskBits = 0x1;
b2CreateCircleShape(bodyId, ref shapeDef, ref circle);

B2Vec2 pivot = new B2Vec2((2.0f * m_count) * hx, m_count * hx);
Expand All @@ -94,6 +99,8 @@ public BallAndChain(SampleContext context) : base(context)
jointDef.localAnchorB = b2Body_GetLocalPoint(jointDef.bodyIdB, pivot);
jointDef.enableMotor = true;
jointDef.maxMotorTorque = m_frictionTorque;
jointDef.enableSpring = true;
jointDef.hertz = 4.0f;
m_jointIds[jointIndex++] = b2CreateRevoluteJoint(m_worldId, ref jointDef);
B2_ASSERT(jointIndex == m_count + 1);
}
Expand Down
66 changes: 50 additions & 16 deletions src/Box2D.NET.Samples/Samples/Joints/Bridge.cs
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Expand Up @@ -26,7 +26,10 @@ public class Bridge : Sample
private B2BodyId[] m_bodyIds = new B2BodyId[m_count];
private B2JointId[] m_jointIds = new B2JointId[m_count + 1];
private float m_frictionTorque;
private float m_gravityScale;
private float m_constraintHertz;
private float m_constraintDampingRatio;
private float m_springHertz;
private float m_springDampingRatio;

private static Sample Create(SampleContext context)
{
Expand All @@ -48,15 +51,25 @@ public Bridge(SampleContext context) : base(context)
}

{
B2Polygon box = b2MakeBox(0.5f, 0.125f);
m_constraintHertz = 60.0f;
m_constraintDampingRatio = 0.0f;
m_springHertz = 2.0f;
m_springDampingRatio = 0.7f;
m_frictionTorque = 200.0f;

B2Polygon box = b2MakeBox( 0.5f, 0.125f );

B2ShapeDef shapeDef = b2DefaultShapeDef();
shapeDef.density = 20.0f;

B2RevoluteJointDef jointDef = b2DefaultRevoluteJointDef();
jointDef.enableMotor = true;
jointDef.maxMotorTorque = m_frictionTorque;
jointDef.enableSpring = true;
jointDef.hertz = m_springHertz;
jointDef.dampingRatio = m_springDampingRatio;

int jointIndex = 0;
m_frictionTorque = 200.0f;
m_gravityScale = 1.0f;

float xbase = -80.0f;

Expand All @@ -76,8 +89,6 @@ public Bridge(SampleContext context) : base(context)
jointDef.bodyIdB = m_bodyIds[i];
jointDef.localAnchorA = b2Body_GetLocalPoint(jointDef.bodyIdA, pivot);
jointDef.localAnchorB = b2Body_GetLocalPoint(jointDef.bodyIdB, pivot);
jointDef.enableMotor = true;
jointDef.maxMotorTorque = m_frictionTorque;
m_jointIds[jointIndex++] = b2CreateRevoluteJoint(m_worldId, ref jointDef);

prevBodyId = m_bodyIds[i];
Expand All @@ -89,8 +100,6 @@ public Bridge(SampleContext context) : base(context)
jointDef.bodyIdB = groundId;
jointDef.localAnchorA = b2Body_GetLocalPoint(jointDef.bodyIdA, pivot);
jointDef.localAnchorB = b2Body_GetLocalPoint(jointDef.bodyIdB, pivot);
jointDef.enableMotor = true;
jointDef.maxMotorTorque = m_frictionTorque;
m_jointIds[jointIndex++] = b2CreateRevoluteJoint(m_worldId, ref jointDef);

B2_ASSERT(jointIndex == m_count + 1);
Expand Down Expand Up @@ -133,15 +142,14 @@ public override void UpdateGui()
{
base.UpdateGui();

float height = 80.0f;
float height = 180.0f;
ImGui.SetNextWindowPos(new Vector2(10.0f, m_camera.m_height - height - 50.0f), ImGuiCond.Once);
ImGui.SetNextWindowSize(new Vector2(240.0f, height));
ImGui.SetNextWindowSize(new Vector2(320.0f, height));

ImGui.Begin("Bridge", ImGuiWindowFlags.NoResize);

// Slider takes half the window
ImGui.PushItemWidth(ImGui.GetWindowWidth() * 0.5f);
bool updateFriction = ImGui.SliderFloat("Joint Friction", ref m_frictionTorque, 0.0f, 1000.0f, "%2.f");
ImGui.PushItemWidth(ImGui.GetWindowWidth() * 0.6f);
bool updateFriction = ImGui.SliderFloat("Joint Friction", ref m_frictionTorque, 0.0f, 10000.0f, "%2.f");
if (updateFriction)
{
for (int i = 0; i <= m_count; ++i)
Expand All @@ -150,14 +158,40 @@ public override void UpdateGui()
}
}

if (ImGui.SliderFloat("Gravity scale", ref m_gravityScale, -1.0f, 1.0f, "%.1f"))
if ( ImGui.SliderFloat( "Spring hertz", ref m_springHertz, 0.0f, 30.0f, "%.0f" ) )
{
for (int i = 0; i < m_count; ++i)
for ( int i = 0; i <= m_count; ++i )
{
b2Body_SetGravityScale(m_bodyIds[i], m_gravityScale);
b2RevoluteJoint_SetSpringHertz( m_jointIds[i], m_springHertz );
}
}

if ( ImGui.SliderFloat( "Spring damping", ref m_springDampingRatio, 0.0f, 2.0f, "%.1f" ) )
{
for ( int i = 0; i <= m_count; ++i )
{
b2RevoluteJoint_SetSpringDampingRatio( m_jointIds[i], m_springDampingRatio );
}
}

if ( ImGui.SliderFloat( "Constraint hertz", ref m_constraintHertz, 15.0f, 240.0f, "%.0f" ) )
{
for ( int i = 0; i <= m_count; ++i )
{
b2Joint_SetConstraintTuning( m_jointIds[i], m_constraintHertz, m_constraintDampingRatio );
}
}

if ( ImGui.SliderFloat( "Constraint damping", ref m_constraintDampingRatio, 0.0f, 10.0f, "%.1f" ) )
{
for ( int i = 0; i <= m_count; ++i )
{
b2Joint_SetConstraintTuning( m_jointIds[i], m_constraintHertz, m_constraintDampingRatio );
}
}

ImGui.PopItemWidth();

ImGui.End();
}
}
25 changes: 19 additions & 6 deletions src/Box2D.NET.Samples/Samples/Joints/Door.cs
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Expand Up @@ -24,6 +24,8 @@ public class Door : Sample
private B2JointId m_jointId;
private float m_impulse;
private float m_translationError;
private float m_jointHertz;
private float m_jointDampingRatio;
private bool m_enableLimit;

private static Sample Create(SampleContext context)
Expand All @@ -47,6 +49,10 @@ public Door(SampleContext context) : base(context)
}

m_enableLimit = true;
m_impulse = 50000.0f;
m_translationError = 0.0f;
m_jointHertz = 240.0f;
m_jointDampingRatio = 1.0f;

{
B2BodyDef bodyDef = b2DefaultBodyDef();
Expand All @@ -62,12 +68,11 @@ public Door(SampleContext context) : base(context)
B2Polygon box = b2MakeBox(0.1f, 1.5f);
b2CreatePolygonShape(m_doorId, ref shapeDef, ref box);

B2Vec2 pivot = new B2Vec2(0.0f, 0.0f);
B2RevoluteJointDef jointDef = b2DefaultRevoluteJointDef();
jointDef.bodyIdA = groundId;
jointDef.bodyIdB = m_doorId;
jointDef.localAnchorA = b2Body_GetLocalPoint(jointDef.bodyIdA, pivot);
jointDef.localAnchorB = b2Body_GetLocalPoint(jointDef.bodyIdB, pivot);
jointDef.localAnchorA = new B2Vec2(0.0f, 0.0f);
jointDef.localAnchorB = new B2Vec2(0.0f, -1.5f);
jointDef.targetAngle = 0.0f;
jointDef.enableSpring = true;
jointDef.hertz = 1.0f;
Expand All @@ -81,10 +86,8 @@ public Door(SampleContext context) : base(context)
jointDef.enableLimit = m_enableLimit;

m_jointId = b2CreateRevoluteJoint(m_worldId, ref jointDef);
b2Joint_SetConstraintTuning(m_jointId, m_jointHertz, m_jointDampingRatio);
}

m_impulse = 50000.0f;
m_translationError = 0.0f;
}

public override void UpdateGui()
Expand All @@ -109,6 +112,16 @@ public override void UpdateGui()
b2RevoluteJoint_EnableLimit(m_jointId, m_enableLimit);
}

if ( ImGui.SliderFloat( "hertz", ref m_jointHertz, 15.0f, 480.0f, "%.0f" ) )
{
b2Joint_SetConstraintTuning( m_jointId, m_jointHertz, m_jointDampingRatio );
}

if ( ImGui.SliderFloat( "damping", ref m_jointDampingRatio, 0.0f, 10.0f, "%.1f" ) )
{
b2Joint_SetConstraintTuning( m_jointId, m_jointHertz, m_jointDampingRatio );
}

ImGui.End();
}

Expand Down
2 changes: 1 addition & 1 deletion src/Box2D.NET.Samples/Samples/Joints/GearLift.cs
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Expand Up @@ -79,7 +79,7 @@ public GearLift(SampleContext context) : base(context)
float linkCount = 40;
float doorHalfHeight = 1.5f;

B2Vec2 gearPosition1 = new B2Vec2(-4.25f, 10.25f);
B2Vec2 gearPosition1 = new B2Vec2(-4.25f, 9.75f);
B2Vec2 gearPosition2 = gearPosition1 + new B2Vec2(2.0f, 1.0f);
B2Vec2 linkAttachPosition = gearPosition2 + new B2Vec2(gearRadius + 2.0f * toothHalfWidth + toothRadius, 0.0f);
B2Vec2 doorPosition = linkAttachPosition - new B2Vec2(0.0f, 2.0f * linkCount * linkHalfLength + doorHalfHeight);
Expand Down
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