b2SurfaceMaterial for chain shapes

include/box2d/types.h

@@ -396,6 +396,35 @@ typedef struct b2ShapeDef
 /// @ingroup shape
 B2_API b2ShapeDef b2DefaultShapeDef( void );
 
+/// Surface materials allow chain shapes to have per segment surface properties.
+/// @ingroup shape
+typedef struct b2SurfaceMaterial
+{
+	/// The Coulomb (dry) friction coefficient, usually in the range [0,1].
+	float friction;
+
+	/// The coefficient of restitution (bounce) usually in the range [0,1].
+	/// https://en.wikipedia.org/wiki/Coefficient_of_restitution
+	float restitution;
+
+	/// The rolling resistance usually in the range [0,1].
+	float rollingResistance;
+
+	/// The tangent speed for conveyor belts
+	float tangentSpeed;
+
+	/// User material identifier. This is passed with query results and to friction and restitution
+	/// combining functions. It is not used internally.
+	int material;
+
+	/// Custom debug draw color.
+	uint32_t customColor;
+} b2SurfaceMaterial;
+
+/// Use this to initialize your surface material
+/// @ingroup shape
+B2_API b2SurfaceMaterial b2DefaultSurfaceMaterial( void );
+
 /// Used to create a chain of line segments. This is designed to eliminate ghost collisions with some limitations.
 /// - chains are one-sided
 /// - chains have no mass and should be used on static bodies
@@ -422,28 +451,19 @@ typedef struct b2ChainDef
 	/// The point count, must be 4 or more.
 	int count;
 
-	/// The friction coefficient, usually in the range [0,1].
-	float friction;
+	/// Surface materials for each segment. These are cloned.
+	const b2SurfaceMaterial* materials;
 
-	/// The restitution (elasticity) usually in the range [0,1].
-	float restitution;
-
-	/// User material identifier. This is passed with query results and to friction and restitution
-	/// combining functions. It is not used internally.
-	int material;
+	/// The material count. Must be 1 or count. This allows you to provide one
+	/// material for all segments or a unique material per segment.
+	int materialCount;
 
 	/// Contact filtering data.
 	b2Filter filter;
 
-	/// Custom debug draw color.
-	uint32_t customColor;
-
 	/// Indicates a closed chain formed by connecting the first and last points
 	bool isLoop;
 
-	/// Generate events when a sensor overlaps this chain
-	bool enableSensorEvents;
-
 	/// Used internally to detect a valid definition. DO NOT SET.
 	int internalValue;
 } b2ChainDef;

samples/sample.cpp

@@ -1,6 +1,8 @@
 // SPDX-FileCopyrightText: 2023 Erin Catto
 // SPDX-License-Identifier: MIT
 
+#define _CRT_SECURE_NO_WARNINGS
+
 #include "sample.h"
 
 #include "TaskScheduler.h"
@@ -118,7 +120,7 @@ Sample::Sample( Settings& settings )
 
 	m_settings = &settings;
 
-	CreateWorld( );
+	CreateWorld();
 	TestMathCpp();
 }
 
@@ -131,7 +133,7 @@ Sample::~Sample()
 	delete[] m_tasks;
 }
 
-void Sample::CreateWorld(  )
+void Sample::CreateWorld()
 {
 	if ( B2_IS_NON_NULL( m_worldId ) )
 	{
@@ -503,6 +505,145 @@ void Sample::ShiftOrigin( b2Vec2 newOrigin )
 	// m_world->ShiftOrigin(newOrigin);
 }
 
+// const char* path =
+// "M 47.625004,185.20833 H 161.39585 l 29.10417,-2.64583 26.45834,-7.9375 26.45833,-13.22917 23.81251,-21.16666 h "
+// "13.22916 v 44.97916 H 592.66669 V 0 h 21.16671 v 206.375 l -566.208398,-1e-5";
+
+int Sample::ParsePath( const char* svgPath, b2Vec2 offset, b2Vec2* points, int capacity, float scale, bool reverseOrder )
+{
+	int pointCount = 0;
+	b2Vec2 currentPoint = {};
+	const char* ptr = svgPath;
+	char command = *ptr;
+
+	while ( *ptr != '\0' )
+	{
+		if ( isdigit( *ptr ) == 0 && *ptr != '-' )
+		{
+			// note: command can be implicitly repeated
+			command = *ptr;
+
+			if ( command == 'M' || command == 'L' || command == 'H' || command == 'V' || command == 'm' || command == 'l' ||
+				 command == 'h' || command == 'v' )
+			{
+				ptr += 2; // Skip the command character and space
+			}
+
+			if ( command == 'z' )
+			{
+				break;
+			}
+		}
+
+		assert( isdigit( *ptr ) != 0 || *ptr == '-' );
+
+		float x = 0.0f, y = 0.0f;
+		switch ( command )
+		{
+			case 'M':
+			case 'L':
+				if ( sscanf( ptr, "%f,%f", &x, &y ) == 2 )
+				{
+					currentPoint.x = x;
+					currentPoint.y = y;
+				}
+				else
+				{
+					assert( false );
+				}
+				break;
+			case 'H':
+				if ( sscanf( ptr, "%f", &x ) == 1 )
+				{
+					currentPoint.x = x;
+				}
+				else
+				{
+					assert( false );
+				}
+				break;
+			case 'V':
+				if ( sscanf( ptr, "%f", &y ) == 1 )
+				{
+					currentPoint.y = y;
+				}
+				else
+				{
+					assert( false );
+				}
+				break;
+			case 'm':
+			case 'l':
+				if ( sscanf( ptr, "%f,%f", &x, &y ) == 2 )
+				{
+					currentPoint.x += x;
+					currentPoint.y += y;
+				}
+				else
+				{
+					assert( false );
+				}
+				break;
+			case 'h':
+				if ( sscanf( ptr, "%f", &x ) == 1 )
+				{
+					currentPoint.x += x;
+				}
+				else
+				{
+					assert( false );
+				}
+				break;
+			case 'v':
+				if ( sscanf( ptr, "%f", &y ) == 1 )
+				{
+					currentPoint.y += y;
+				}
+				else
+				{
+					assert( false );
+				}
+				break;
+
+			default:
+				assert( false );
+				break;
+		}
+
+		points[pointCount] = { scale * ( currentPoint.x + offset.x ), -scale * ( currentPoint.y + offset.y ) };
+		pointCount += 1;
+		if ( pointCount == capacity )
+		{
+			break;
+		}
+
+		// Move to the next space or end of string
+		while ( *ptr != '\0' && isspace( *ptr ) == 0 )
+		{
+			ptr++;
+		}
+
+		// Skip contiguous spaces
+		while ( isspace( *ptr ) )
+		{
+			ptr++;
+		}
+
+		ptr += 0;
+	}
+
+	if ( pointCount == 0 )
+	{
+		return 0;
+	}
+
+	if ( reverseOrder )
+	{
+
+	}
+	return pointCount;
+}
+
 SampleEntry g_sampleEntries[MAX_SAMPLES] = {};
 int g_sampleCount = 0;
 

samples/sample.h

@@ -60,6 +60,8 @@ class Sample
 	void ResetProfile();
 	void ShiftOrigin( b2Vec2 newOrigin );
 
+	static int ParsePath( const char* svgPath, b2Vec2 offset, b2Vec2* points, int capacity, float scale, bool reverseOrder );
+
 	friend class DestructionListener;
 	friend class BoundaryListener;
 	friend class ContactListener;

samples/sample_continuous.cpp

@@ -667,11 +667,15 @@ class GhostBumps : public Sample
 			points[18] = b2Add( points[17], { -2.0f * hx, 0.0f } );
 			points[19] = b2Add( points[18], { -2.0f * hx, 0.0f } );
 
+			b2SurfaceMaterial material = {};
+			material.friction = m_friction;
+
 			b2ChainDef chainDef = b2DefaultChainDef();
 			chainDef.points = points;
 			chainDef.count = 20;
 			chainDef.isLoop = true;
-			chainDef.friction = m_friction;
+			chainDef.materials = &material;
+			chainDef.materialCount = 1;
 
 			b2CreateChain( m_groundId, &chainDef );
 		}

samples/sample_events.cpp

@@ -92,11 +92,15 @@ class SensorFunnel : public Sample
 			// }
 			// printf("};\n");
 
+			b2SurfaceMaterial material = {};
+			material.friction = 0.2f;
+
 			b2ChainDef chainDef = b2DefaultChainDef();
 			chainDef.points = points;
 			chainDef.count = count;
 			chainDef.isLoop = true;
-			chainDef.friction = 0.2f;
+			chainDef.materials = &material;
+			chainDef.materialCount = 1;
 			b2CreateChain( groundId, &chainDef );
 
 			float sign = 1.0f;