[upstream] Simplified island merging, revised motor joint (box2d #966)

- simplified island merging. Islands are now immediately merged when a
contact or joint are linked.
- motor joint now has spring target and velocity target functionality
- distance joint now has tension and compression force limits for the
spring
- samples now use the motor joint instead of the mouse joint

#964 #960 #961 #959 #958

Author: ikpil

src/Box2D.NET.Samples/Samples/Benchmarks/BenchmarkBarrel24.cs

@@ -0,0 +1,91 @@
+using static Box2D.NET.B2Geometries;
+using static Box2D.NET.B2Types;
+using static Box2D.NET.B2MathFunction;
+using static Box2D.NET.B2Bodies;
+using static Box2D.NET.B2Shapes;
+
+namespace Box2D.NET.Samples.Samples.Benchmarks;
+
+// This is used to compare performance with Box2D v2.4
+public class BenchmarkBarrel24 : Sample
+{
+    private static readonly int benchmarkBarrel24 = SampleFactory.Shared.RegisterSample("Benchmark", "Barrel 2.4", Create);
+
+    private static Sample Create(SampleContext context)
+    {
+        return new BenchmarkBarrel24(context);
+    }
+
+    public BenchmarkBarrel24(SampleContext context) : base(context)
+    {
+        if (m_context.settings.restart == false)
+        {
+            m_context.camera.m_center = new B2Vec2(8.0f, 53.0f);
+            m_context.camera.m_zoom = 25.0f * 2.35f;
+        }
+
+        float groundSize = 25.0f;
+
+        {
+            B2BodyDef bodyDef = b2DefaultBodyDef();
+            B2BodyId groundId = b2CreateBody(m_worldId, ref bodyDef);
+
+            B2Polygon box = b2MakeBox(groundSize, 1.2f);
+            B2ShapeDef shapeDef = b2DefaultShapeDef();
+            b2CreatePolygonShape(groundId, ref shapeDef, ref box);
+
+            bodyDef.rotation = b2MakeRot(0.5f * B2_PI);
+            bodyDef.position = new B2Vec2(groundSize, 2.0f * groundSize);
+            groundId = b2CreateBody(m_worldId, ref bodyDef);
+
+            box = b2MakeBox(2.0f * groundSize, 1.2f);
+            b2CreatePolygonShape(groundId, ref shapeDef, ref box);
+
+            bodyDef.position = new B2Vec2(-groundSize, 2.0f * groundSize);
+            groundId = b2CreateBody(m_worldId, ref bodyDef);
+            b2CreatePolygonShape(groundId, ref shapeDef, ref box);
+        }
+
+        int num = 26;
+        float rad = 0.5f;
+
+        float shift = rad * 2.0f;
+        float centerx = shift * num / 2.0f;
+        float centery = shift / 2.0f;
+
+        {
+            B2BodyDef bodyDef = b2DefaultBodyDef();
+            bodyDef.type = B2BodyType.b2_dynamicBody;
+
+            B2ShapeDef shapeDef = b2DefaultShapeDef();
+            shapeDef.density = 1.0f;
+            shapeDef.material.friction = 0.5f;
+
+            B2Polygon cuboid = b2MakeSquare(0.5f);
+
+            // b2Polygon top = b2MakeOffsetBox(0.8f, 0.2f, {0.0f, 0.8f}, 0.0f);
+            // b2Polygon leftLeg = b2MakeOffsetBox(0.2f, 0.5f, {-0.6f, 0.5f}, 0.0f);
+            // b2Polygon rightLeg = b2MakeOffsetBox(0.2f, 0.5f, {0.6f, 0.5f}, 0.0f);
+
+#if DEBUG
+            int numj = 5;
+#else
+		int numj = 5 * num;
+#endif
+            for (int i = 0; i < num; ++i)
+            {
+                float x = i * shift - centerx;
+
+                for (int j = 0; j < numj; ++j)
+                {
+                    float y = j * shift + centery + 2.0f;
+
+                    bodyDef.position = new B2Vec2(x, y);
+
+                    B2BodyId bodyId = b2CreateBody(m_worldId, ref bodyDef);
+                    b2CreatePolygonShape(bodyId, ref shapeDef, ref cuboid);
+                }
+            }
+        }
+    }
+}

src/Box2D.NET.Samples/Samples/Benchmarks/BenchmarkCapacity.cs

@@ -0,0 +1,95 @@
+using static Box2D.NET.B2Geometries;
+using static Box2D.NET.B2Types;
+using static Box2D.NET.B2Bodies;
+using static Box2D.NET.B2Shapes;
+using static Box2D.NET.B2Worlds;
+
+namespace Box2D.NET.Samples.Samples.Benchmarks;
+
+public class BenchmarkCapacity : Sample
+{
+    private static readonly int benchmarkCapacity = SampleFactory.Shared.RegisterSample("Benchmark", "Capacity", Create);
+
+    private B2Polygon m_square;
+    private int m_reachCount;
+    private bool m_done;
+
+    private static Sample Create(SampleContext context)
+    {
+        return new BenchmarkCapacity(context);
+    }
+
+    public BenchmarkCapacity(SampleContext context) : base(context)
+    {
+        if (m_context.settings.restart == false)
+        {
+            m_context.camera.m_center = new B2Vec2(0.0f, 150.0f);
+            m_context.camera.m_zoom = 200.0f;
+        }
+
+        {
+            B2BodyDef bodyDef = b2DefaultBodyDef();
+            bodyDef.position.Y = -5.0f;
+            B2BodyId groundId = b2CreateBody(m_worldId, ref bodyDef);
+
+            B2Polygon box = b2MakeBox(800.0f, 5.0f);
+            B2ShapeDef shapeDef = b2DefaultShapeDef();
+            b2CreatePolygonShape(groundId, ref shapeDef, ref box);
+        }
+
+        m_square = b2MakeSquare(0.5f);
+        m_done = false;
+        m_reachCount = 0;
+    }
+
+    public override void Step()
+    {
+        base.Step();
+
+        float millisecondLimit = 20.0f;
+
+        B2Profile profile = b2World_GetProfile(m_worldId);
+        if (profile.step > millisecondLimit)
+        {
+            m_reachCount += 1;
+            if (m_reachCount > 60)
+            {
+                // Hit the millisecond limit 60 times in a row
+                m_done = true;
+            }
+        }
+        else
+        {
+            m_reachCount = 0;
+        }
+
+        if (m_done == true)
+        {
+            return;
+        }
+
+        if ((m_stepCount & 0x1F) != 0x1F)
+        {
+            return;
+        }
+
+        B2BodyDef bodyDef = b2DefaultBodyDef();
+        bodyDef.type = B2BodyType.b2_dynamicBody;
+        bodyDef.position.Y = 200.0f;
+
+        B2ShapeDef shapeDef = b2DefaultShapeDef();
+
+        int count = 200;
+        float x = -1.0f * count;
+        for (int i = 0; i < count; ++i)
+        {
+            bodyDef.position.X = x;
+            bodyDef.position.Y += 0.5f;
+
+            B2BodyId bodyId = b2CreateBody(m_worldId, ref bodyDef);
+            b2CreatePolygonShape(bodyId, ref shapeDef, ref m_square);
+
+            x += 2.0f;
+        }
+    }
+}

src/Box2D.NET.Samples/Samples/Benchmarks/BenchmarkSensor.cs

@@ -83,13 +83,25 @@ public BenchmarkSensor(SampleContext context) : base(context)
             shapeDef.enableSensorEvents = true;
 
             float yStart = 10.0f;
-
+            m_filterRow = m_rowCount >> 1;
+            
             for (int j = 0; j < m_rowCount; ++j)
             {
                 m_passiveSensors[j] = new ShapeUserData();
                 m_passiveSensors[j].row = j;
                 m_passiveSensors[j].active = false;
                 shapeDef.userData = m_passiveSensors[j];
+                
+                if ( j == m_filterRow )
+                {
+                    shapeDef.enableCustomFiltering = true;
+                    shapeDef.material.customColor = (uint)B2HexColor.b2_colorFuchsia;
+                }
+                else
+                {
+                    shapeDef.enableCustomFiltering = false;
+                    shapeDef.material.customColor = 0;
+                }
 
                 float y = j * shift + yStart;
                 for (int i = 0; i < m_columnCount; ++i)
@@ -104,7 +116,6 @@ public BenchmarkSensor(SampleContext context) : base(context)
         m_maxBeginCount = 0;
         m_maxEndCount = 0;
         m_lastStepCount = 0;
-        m_filterRow = m_rowCount >> 1;
     }
 
     void CreateRow(float y)

src/Box2D.NET.Samples/Samples/Continuous/ChainDrop.cs

@@ -77,7 +77,7 @@ void Launch()
         B2Circle circle = new B2Circle(new B2Vec2(0.0f, 0.0f), 0.5f);
         m_shapeId = b2CreateCircleShape(m_bodyId, ref shapeDef, ref circle);
 
-        //b2Capsule capsule = { { -0.5f, 0.0f }, { 0.5f, 0.0 }, 0.25f };
+        //b2Capsule capsule = { { -0.5f, 0.0f }, { 0.5f, 0.0f }, 0.25f };
         //m_shapeId = b2CreateCapsuleShape( m_bodyId, &shapeDef, &capsule );
 
         //float h = 0.5f;

src/Box2D.NET.Samples/Samples/Events/JointEvent.cs

@@ -99,8 +99,8 @@ public JointEvent(SampleContext context) : base(context)
             jointDef.@base.bodyIdA = groundId;
             jointDef.@base.bodyIdB = bodyId;
             jointDef.@base.localFrameA.p = position;
-            jointDef.maxForce = 1000.0f;
-            jointDef.maxTorque = 20.0f;
+            jointDef.maxVelocityForce = 1000.0f;
+            jointDef.maxVelocityTorque = 20.0f;
             jointDef.@base.forceThreshold = forceThreshold;
             jointDef.@base.torqueThreshold = torqueThreshold;
             jointDef.@base.collideConnected = true;

src/Box2D.NET.Samples/Samples/Joints/BreakableJoint.cs

@@ -95,8 +95,8 @@ public BreakableJoint(SampleContext context) : base(context)
             jointDef.@base.bodyIdA = groundId;
             jointDef.@base.bodyIdB = bodyId;
             jointDef.@base.localFrameA.p = position;
-            jointDef.maxForce = 1000.0f;
-            jointDef.maxTorque = 20.0f;
+            jointDef.maxVelocityForce = 1000.0f;
+            jointDef.maxVelocityTorque = 20.0f;
             jointDef.@base.collideConnected = true;
             m_jointIds[index] = b2CreateMotorJoint(m_worldId, ref jointDef);
         }

src/Box2D.NET.Samples/Samples/Joints/DistanceJoint.cs

@@ -27,6 +27,8 @@ public class DistanceJoint : Sample
     private float m_hertz;
     private float m_dampingRatio;
     private float m_length;
+    private float m_tensionForce;
+    private float m_compressionForce;
     private float m_minLength;
     private float m_maxLength;
     private bool m_enableSpring;
@@ -51,11 +53,13 @@ public DistanceJoint(SampleContext context) : base(context)
         }
 
         m_count = 0;
-        m_hertz = 2.0f;
+        m_hertz = 5.0f;
         m_dampingRatio = 0.5f;
         m_length = 1.0f;
         m_minLength = m_length;
         m_maxLength = m_length;
+        m_tensionForce = 2000.0f;
+        m_compressionForce = 100.0f;        
         m_enableSpring = false;
         m_enableLimit = false;
 
@@ -97,6 +101,8 @@ void CreateScene(int newCount)
         jointDef.hertz = m_hertz;
         jointDef.dampingRatio = m_dampingRatio;
         jointDef.length = m_length;
+        jointDef.lowerSpringForce = -m_tensionForce;
+        jointDef.upperSpringForce = m_compressionForce;
         jointDef.minLength = m_minLength;
         jointDef.maxLength = m_maxLength;
         jointDef.enableSpring = m_enableSpring;
@@ -107,7 +113,7 @@ void CreateScene(int newCount)
         {
             B2BodyDef bodyDef = b2DefaultBodyDef();
             bodyDef.type = B2BodyType.b2_dynamicBody;
-            bodyDef.angularDamping = 0.1f;
+            bodyDef.angularDamping = 1.0f;
             bodyDef.position = new B2Vec2(m_length * (i + 1.0f), yOffset);
             m_bodyIds[i] = b2CreateBody(m_worldId, ref bodyDef);
             b2CreateCircleShape(m_bodyIds[i], ref shapeDef, ref circle);
@@ -129,12 +135,12 @@ public override void UpdateGui()
         base.UpdateGui();
 
         float fontSize = ImGui.GetFontSize();
-        float height = 240.0f;
+        float height = 20.0f * fontSize;
         ImGui.SetNextWindowPos(new Vector2(0.5f * fontSize, m_camera.m_height - height - 2.0f * fontSize), ImGuiCond.Once);
-        ImGui.SetNextWindowSize(new Vector2(180.0f, height));
+        ImGui.SetNextWindowSize(new Vector2(18.0f * fontSize, height));
 
         ImGui.Begin("Distance Joint", ImGuiWindowFlags.NoResize);
-        ImGui.PushItemWidth(100.0f);
+        ImGui.PushItemWidth(10.0f * fontSize);
 
         if (ImGui.SliderFloat("Length", ref m_length, 0.1f, 4.0f, "%3.1f"))
         {
@@ -156,6 +162,25 @@ public override void UpdateGui()
 
         if (m_enableSpring)
         {
+            
+            if ( ImGui.SliderFloat( "Tension", ref m_tensionForce, 0.0f, 4000.0f ) )
+            {
+                for ( int i = 0; i < m_count; ++i )
+                {
+                    b2DistanceJoint_SetSpringForceRange( m_jointIds[i], -m_tensionForce, m_compressionForce );
+                    b2Joint_WakeBodies( m_jointIds[i] );
+                }
+            }
+
+            if ( ImGui.SliderFloat( "Compression", ref m_compressionForce, 0.0f, 200.0f ) )
+            {
+                for ( int i = 0; i < m_count; ++i )
+                {
+                    b2DistanceJoint_SetSpringForceRange( m_jointIds[i], -m_tensionForce, m_compressionForce );
+                    b2Joint_WakeBodies( m_jointIds[i] );
+                }
+            }
+            
             if (ImGui.SliderFloat("Hertz", ref m_hertz, 0.0f, 15.0f, "%3.1f"))
             {
                 for (int i = 0; i < m_count; ++i)

src/Box2D.NET.Samples/Samples/Joints/MotionLocks.cs

@@ -93,8 +93,8 @@ public MotionLocks(SampleContext context) : base(context)
             jointDef.@base.bodyIdA = groundId;
             jointDef.@base.bodyIdB = m_bodyIds[index];
             jointDef.@base.localFrameA.p = position;
-            jointDef.maxForce = 200.0f;
-            jointDef.maxTorque = 200.0f;
+            jointDef.maxVelocityForce = 200.0f;
+            jointDef.maxVelocityTorque = 200.0f;
             b2CreateMotorJoint(m_worldId, ref jointDef);
         }