Using Jolt's math in the multi threaded conveyor belt contact listener (#212)

Fixed conveyor belt example to be thread safe

Author: jrouwe

CMakeLists.txt

@@ -59,10 +59,12 @@ if (ENABLE_MULTI_THREADING)
 		-s PTHREAD_POOL_SIZE=16)
 	set(CMAKE_CXX_FLAGS "-pthread -s SHARED_MEMORY")
 	set(OUTPUT_BASE_NAME "${OUTPUT_FOLDER}jolt-physics.multithread")
+	set(WEBIDL_PARAMS "--thread_safe")
 else()
 	set(MULTI_THREADED_FLAG "")
 	set(ENVIRONMENT_FLAG "-s ENVIRONMENT='web,node'")
 	set(OUTPUT_BASE_NAME "${OUTPUT_FOLDER}jolt-physics")
+	set(WEBIDL_PARAMS "")
 endif()
 
 # Enable SIMD flags
@@ -199,7 +201,7 @@ add_custom_command(
 	OUTPUT glue.cpp glue.js jolt.idl
 	BYPRODUCTS parser.out WebIDLGrammar.pkl
 	COMMAND cat ${JOLT_IDL_FILE} > jolt.idl
-	COMMAND ${PYTHON} ${WEBIDL_BINDER_SCRIPT} jolt.idl glue
+	COMMAND ${PYTHON} ${WEBIDL_BINDER_SCRIPT} jolt.idl glue ${WEBIDL_PARAMS}
 	DEPENDS ${JOLT_IDL_FILE}
 	COMMENT "Generating JoltPhysics.js bindings"
 	VERBATIM)

Examples/conveyor_belt_threaded.html

@@ -20,12 +20,15 @@
 		<script src="js/example.js"></script>
 
 		<script id="workerScript" type="module">
-			import * as THREE from 'https://cdn.jsdelivr.net/npm/[email protected]/build/three.module.min.js';
-
-			const wrapQuat = (q) => new THREE.Quaternion(q.GetX(), q.GetY(), q.GetZ(), q.GetW());
-			const wrapVec3 = (v) => new THREE.Vector3(v.GetX(), v.GetY(), v.GetZ());
-			const DegreesToRadians = (deg) => deg * (Math.PI / 180.0);
 			const onWorker = globalThis.onWorker = async (Jolt, args) => {
+				Jolt.Vec3.prototype.Clone = function () { return new Jolt.Vec3(this.GetX(), this.GetY(), this.GetZ()); };
+				Jolt.RVec3.prototype.Clone = function () { return new Jolt.RVec3(this.GetX(), this.GetY(), this.GetZ()); };
+				Jolt.Quat.prototype.Clone = function () { return new Jolt.Quat(this.GetX(), this.GetY(), this.GetZ(), this.GetW()); };
+				const DegreesToRadians = (deg) => deg * (Math.PI / 180.0);
+
+				const cLocalSpaceVelocity = new Jolt.Vec3(0, 0, -10.0);
+				const cLocalSpaceAngularVelocity = new Jolt.Vec3(0, DegreesToRadians(10.0), 0);
+
 				const { contactListenerPtr, linearBelts, angularBelt } = args;
 				const contactListener = Jolt.wrapPointer(contactListenerPtr, Jolt.ContactListenerJS);
 
@@ -37,44 +40,39 @@
 
 					const body1ID = body1.GetID().GetIndexAndSequenceNumber();
 					const body2ID = body2.GetID().GetIndexAndSequenceNumber();
-					const rotation1 = wrapQuat(body1.GetRotation());
-					const rotation2 = wrapQuat(body2.GetRotation());
+					const rotation1 = body1.GetRotation().Clone(); // Next call to GetRotation() will overwrite rotation1
+					const rotation2 = body2.GetRotation();
 
 					const body1LinearBelt = linearBelts.find(belt => belt == body1ID)
 					const body2LinearBelt = linearBelts.find(belt => belt == body2ID)
 					if (body1LinearBelt || body2LinearBelt) {
 						// Determine the world space surface velocity of both bodies
-						const cLocalSpaceVelocity = new THREE.Vector3(0, 0, -10.0);
-						const body1LinearSurfaceVelocity = body1LinearBelt ? cLocalSpaceVelocity.applyQuaternion(rotation1) : new THREE.Vector3(0, 0, 0);
-						const body2LinearSurfaceVelocity = body2LinearBelt ? cLocalSpaceVelocity.applyQuaternion(rotation2) : new THREE.Vector3(0, 0, 0);
+						const body1LinearSurfaceVelocity = body1LinearBelt ? rotation1.MulVec3(cLocalSpaceVelocity).Clone() : new Jolt.Vec3(0, 0, 0);
+						const body2LinearSurfaceVelocity = body2LinearBelt ? rotation2.MulVec3(cLocalSpaceVelocity).Clone() : new Jolt.Vec3(0, 0, 0);
 
 						// Calculate the relative surface velocity
-						const v = body2LinearSurfaceVelocity.sub(body1LinearSurfaceVelocity);
-						settings.mRelativeLinearSurfaceVelocity.Set(v.x, v.y, v.z);
+						body2LinearSurfaceVelocity.Sub(body1LinearSurfaceVelocity);
+						settings.mRelativeLinearSurfaceVelocity = body2LinearSurfaceVelocity;
 					}
 
 					const angularBodyId = angularBelt[0];
 					const body1Angular = body1ID == angularBodyId;
 					const body2Angular = body2ID == angularBodyId;
 					if (body1Angular || body2Angular) {
 						// Determine the world space angular surface velocity of both bodies
-						const cLocalSpaceAngularVelocity = new THREE.Vector3(0, DegreesToRadians(10.0), 0);
-						const body1AngularSurfaceVelocity = body1Angular ? cLocalSpaceAngularVelocity.applyQuaternion(rotation1) : new THREE.Vector3(0, 0, 0);
-						const body2AngularSurfaceVelocity = body2Angular ? cLocalSpaceAngularVelocity.applyQuaternion(rotation2) : new THREE.Vector3(0, 0, 0);
+						const body1AngularSurfaceVelocity = body1Angular ? rotation1.MulVec3(cLocalSpaceAngularVelocity).Clone() : new Jolt.Vec3(0, 0, 0);
+						const body2AngularSurfaceVelocity = body2Angular ? rotation2.MulVec3(cLocalSpaceAngularVelocity).Clone() : new Jolt.Vec3(0, 0, 0);
 
 						// Note that the angular velocity is the angular velocity around body 1's center of mass, so we need to add the linear velocity of body 2's center of mass
-						const COM1 = wrapVec3(body1.GetCenterOfMassPosition());
-						const COM2 = wrapVec3(body2.GetCenterOfMassPosition());
-						const body2LinearSurfaceVelocity = body2Angular ?
-							body2AngularSurfaceVelocity.cross(COM1.clone().sub(COM2)) : new THREE.Vector3(0, 0, 0);
+						const COM1 = body1.GetCenterOfMassPosition().Clone();
+						const COM2 = body2.GetCenterOfMassPosition();
+						const body2LinearSurfaceVelocity = body2Angular ? body2AngularSurfaceVelocity.Cross(COM1.Sub(COM2)).Clone() : new Jolt.Vec3(0, 0, 0);
 
 						// Calculate the relative angular surface velocity
-						const rls = body2LinearSurfaceVelocity;
-						settings.mRelativeLinearSurfaceVelocity.Set(rls.x, rls.y, rls.z);
-						const ras = body2AngularSurfaceVelocity.sub(body1AngularSurfaceVelocity);
-						settings.mRelativeAngularSurfaceVelocity.Set(ras.x, ras.y, ras.z);
+						settings.mRelativeLinearSurfaceVelocity = body2LinearSurfaceVelocity;
+						body2AngularSurfaceVelocity.Sub(body1AngularSurfaceVelocity);
+						settings.mRelativeAngularSurfaceVelocity = body2AngularSurfaceVelocity;
 					}
-
 				};
 				contactListener.OnContactPersisted = (body1, body2, manifold, settings) => {
 					// Same behavior as contact added

Examples/stress_test_threaded.html

@@ -4,7 +4,7 @@
 		<title>JoltPhysics.js demo</title>
 		<meta charset="utf-8">
 		<meta name="viewport" content="width=device-width, user-scalable=no, minimum-scale=1.0, maximum-scale=1.0">
-		<script src="js/coi-serviceworker.min.js"></script>
+		<script src="coi-serviceworker.min.js"></script>
 		<link rel="stylesheet" type="text/css" href="style.css">
 	</head>
 	<body>

README.md

@@ -13,10 +13,12 @@ Go to the [demos page](https://jrouwe.github.io/JoltPhysics.js/) to see the proj
 
 ## Using
 
-This library comes in 3 flavours:
+This library comes in 5 flavours:
 - `wasm-compat` - A WASM version with the WASM file (encoded in base64) embedded in the bundle
 - `wasm` - A WASM version with a separate WASM file
 - `asm` - A JavaScript version that uses [asm.js](https://developer.mozilla.org/en-US/docs/Games/Tools/asm.js)
+- `wasm-compat-multithread` - Same as `wasm-compat` but with multi threading and SIMD enabled.
+- `wasm-multithread` - Same as `wasm` but with multi threading and SIMD enabled.
 
 See [falling_shapes.html](Examples/falling_shapes.html) for a example on how to use the library.
 
@@ -46,6 +48,12 @@ import Jolt from 'jolt-physics/wasm';
 
 // asm.js
 import Jolt from 'jolt-physics/asm';
+
+// WASM embedded in the bundle, multithread and SIMD enabled
+import Jolt from 'jolt-physics/wasm-compat-multithread';
+
+// WASM, multithread and SIMD enabled
+import Jolt from 'jolt-physics/wasm-multithread';
 ```
 
 You can also import esm bundles with unpkg:
@@ -95,7 +103,7 @@ Additional options that can be provided to ```build.sh```:
 
 ## Running
 
-By default the examples use the WASM version of Jolt. This requires serving the html file using a web server rather than opening the html file directly.
+By default the examples use the WASM compat version of Jolt. This requires serving the html file using a web server rather than opening the html file directly.
 
 Go open a terminal in this folder and run the following commands:
 

tools/README.md

@@ -1,3 +1,5 @@
 The files in this folder are modified versions of https://github.com/emscripten-core/emscripten/tree/main/tools and https://github.com/emscripten-core/emscripten/tree/main/third_party at version 10cb9d46cdd17e7a96de68137c9649d9a630fbc7
 
-They are here until this PR is merged: https://github.com/emscripten-core/emscripten/pull/22770
+They are here until these PRs are merged:
+- https://github.com/emscripten-core/emscripten/pull/22770
+- https://github.com/emscripten-core/emscripten/pull/22772

tools/webidl_binder.py

@@ -59,6 +59,8 @@ def getExtendedAttribute(self, _name):
 parser = argparse.ArgumentParser()
 parser.add_argument('--wasm64', action='store_true', default=False,
                     help='Build for wasm64')
+parser.add_argument('--thread_safe', action='store_true', default=False,
+                    help='Emit temporaries as "static thread_local" to avoid race conditions')
 parser.add_argument('infile')
 parser.add_argument('outfile')
 options = parser.parse_args()
@@ -388,7 +390,7 @@ def type_to_cdec(raw):
 
 def render_function(class_name, func_name, sigs, return_type, non_pointer,
                     copy, operator, constructor, is_static, func_scope,
-                    call_content=None, const=False, array_attribute=False):
+                    call_content=None, const=False, array_attribute=False, thread_safe=False):
   legacy_mode = CHECKS not in ['ALL', 'FAST']
   all_checks = CHECKS == 'ALL'
 
@@ -624,10 +626,13 @@ def make_call_args(i):
     basic_return = 'return ' if constructor or return_type != 'Void' else ''
     return_prefix = basic_return
     return_postfix = ''
+    storage_attribute = ''
     if non_pointer:
       return_prefix += '&'
+    if thread_safe:
+      storage_attribute = 'thread_local '
     if copy:
-      pre += '  static %s temp;\n' % type_to_c(return_type, non_pointing=True)
+      pre += '  static %s%s temp;\n' % (storage_attribute, type_to_c(return_type, non_pointing=True))
       return_prefix += '(temp = '
       return_postfix += ', &temp)'
 
@@ -765,7 +770,8 @@ def add_bounds_check_impl():
                     constructor,
                     is_static=m.isStatic(),
                     func_scope=m.parentScope.identifier.name,
-                    const=m.getExtendedAttribute('Const'))
+                    const=m.getExtendedAttribute('Const'),
+                    thread_safe=options.thread_safe)
     mid_js += ['\n']
     if constructor:
       mid_js += build_constructor(name)
@@ -807,7 +813,8 @@ def add_bounds_check_impl():
                     func_scope=interface,
                     call_content=get_call_content,
                     const=m.getExtendedAttribute('Const'),
-                    array_attribute=m.type.isArray())
+                    array_attribute=m.type.isArray(),
+                    thread_safe=options.thread_safe)
 
     if m.readonly:
       mid_js += [r'''
@@ -829,7 +836,8 @@ def add_bounds_check_impl():
                       func_scope=interface,
                       call_content=set_call_content,
                       const=m.getExtendedAttribute('Const'),
-                      array_attribute=m.type.isArray())
+                      array_attribute=m.type.isArray(),
+                      thread_safe=options.thread_safe)
       mid_js += [r'''
 /** @suppress {checkTypes} */
 Object.defineProperty(%s.prototype, '%s', { get: %s.prototype.%s, set: %s.prototype.%s });
@@ -847,7 +855,8 @@ def add_bounds_check_impl():
                     False,
                     False,
                     func_scope=interface,
-                    call_content='delete self')
+                    call_content='delete self',
+                    thread_safe=options.thread_safe)
 
   # Emit C++ class implementation that calls into JS implementation