How to add Ammo.js Physics to MD2Character?

[Maykel_Fernandez]

Hello! I found an example where Quake2 models were loaded in three.js. I wanted to do something like a battle royale but I had a little problem. I wanted to use Ammo.js for physics.
I added physics to the ground so that the character can walk on it.
But when I wanted to do the same with the player I got an error.

I use this code for the rigid bodies:

	let createMeshRigidBody = function(geometry,mesh,mass) {
		// new empty ammo shape
		const shape = new Ammo.btConvexHullShape();
		
		//new ammo triangles
		let triangle, triangle_mesh = new Ammo.btTriangleMesh;
		
		//new ammo vectors
		let vectA = new Ammo.btVector3(0,0,0);
		let vectB = new Ammo.btVector3(0,0,0);
		let vectC = new Ammo.btVector3(0,0,0);
		
		//retrieve vertices positions from object
		let verticesPos = geometry.getAttribute('position').array;
		let triangles = [];
		for ( let i = 0; i < verticesPos.length; i += 3 ) {
			triangles.push({ x:verticesPos[i], y:verticesPos[i+1], z:verticesPos[i+2] })
		}
		
		//use triangles data to draw ammo shape
		for ( let i = 0; i < triangles.length-3; i += 3 ) {
			vectA.setX(triangles[i].x);
			vectA.setY(triangles[i].y);
			vectA.setZ(triangles[i].z);
			shape.addPoint(vectA,true);
			
			vectB.setX(triangles[i+1].x);
			vectB.setY(triangles[i+1].y);
			vectB.setZ(triangles[i+1].z);
			shape.addPoint(vectB,true);
			
			vectC.setX(triangles[i+2].x);
			vectC.setY(triangles[i+2].y);
			vectC.setZ(triangles[i+2].z);
			shape.addPoint(vectC,true);
			
			triangle_mesh.addTriangle( vectA, vectB, vectC, true );
			
		}
		
		let quaternion = mesh.quaternion;
		
		let position = mesh.position;
		
		let transform = new Ammo.btTransform();
		transform.setIdentity();
		transform.setOrigin( new Ammo.btVector3( position.x, position.y, position.z ) );
		transform.setRotation( new Ammo.btQuaternion( quaternion.x, quaternion.y, quaternion.z, quaternion.w ) );
		
		let defaultMotionState = new Ammo.btDefaultMotionState( transform );
				
		let localInertia = new Ammo.btVector3( 0, 0, 0 );
		shape.calculateLocalInertia( mass, localInertia );
		let RBody_Info = new Ammo.btRigidBodyConstructionInfo( mass, defaultMotionState, shape, localInertia );
		let RBody = new Ammo.btRigidBody( RBody_Info );
		ammoWorld.addRigidBody( RBody );
		mesh.userData.physicsBody = RBody;
		rigidBody_List.push(mesh);
		
	};

I call: this.createMeshRigidBody( ground_geom, ground_mesh, 0 ); for the ground.

And this function creates a new player:

	createPlayer: function () {
		var that = this;
		// CHARACTER
		player = new THREE.MD2CharacterComplex();
		player.scale = 3;
		player.controls = controls;
		playerConf = Characters[selectedPlayer-1];
		var baseCharacter = new THREE.MD2CharacterComplex();
		baseCharacter.scale = 3;
		baseCharacter.onLoadComplete = function () {
			player.shareParts( baseCharacter );
			player.enableShadows( true );
			player.root.castShadow = true;
			if (playerConf.equipWeapon) player.setWeapon( 0 );
			player.setSkin( 0 );
			player.root.position.x = 0;
			player.root.position.z = 0;
			scene.add( player.root );
			camera.position.set(0,150,-400);
			camera2.position.copy(camera.position);
			camera.lookAt( player.root.position );
			player.root.add( camera );
			player.root.add( camera2 );
			player.root.add( orbit.target );
			gameReady = true;
			// physics
			var geom = new THREE.Geometry();
			// i do this with obj
geom.fromBufferGeometry(player.meshBody);
			that.createMeshRigidBody( geom, player.meshBody, 0 );   // i cant get the geometry
			that.createControls();
		};
		baseCharacter.loadParts( playerConf );
	}

I use MD2CharacterComplex.js to create the player. It’s ok if you just want to move it, but i want it to be able to jump, fall, collide with the walls.

please… can someone help me ?.

[Oxyn]

seem you are using THREE.Geometry it’s gone since release 125.

The rest is close to my take on the topic (using early templates from Doob+Blue’s articles) so you not that far from a working answer.
https://github.com/Oxynt/AmmoPhysics-extended

My guess would be to keep everything you have, only changing the way you get the geometry data.

[Maykel_Fernandez]

Hi. Im working with Revision79, so THREE.Geometry stills there.
I think the meshes may have a reference to their geometry as property.
What I want is to get the geometry with which the mesh was created.
Another thing is the mesh is a THREE.MorphBlendMesh.
Is unknown for me

[Oxyn]

that’s a pretty old version
The first step is to output a log of your mesh in your browser, something like: console.log(myMesh)
Ammo need a specific geometry attribute: Float32BufferAttribute, and I fear yours is not compatible.

This is a common issue when using mesh from loaders (like GLTF and other add-ons)

A possible fix is to use a hidden function from BufferGeometryUtils.js https://github.com/mrdoob/three.js/pull/23814/files
It was included to ease the workflow with physics/BVH engines on custom mesh.
Further informations about the process can be found here: three.js - How to get regular float32 geometry of a mesh compressed using gltfpack - Stack Overflow

But to be honest…your three version is so old you may be forced to rewrite your own attribute quantizing function for THREE.MorphBlendMesh

[Maykel_Fernandez]

The reason I use R79 is because it is easier to understand. I’m not new to JavaScript, but I am programming in 3D.

Those are screenshots of the scene running.

The solution was adding a box geometry for the player body

	this.createPlayerRigidBody = function(player,mass) {
		let scale = 25;
		let playerBox = new THREE.BoxBufferGeometry(scale,scale,scale);
		let weaponBox = new THREE.BoxBufferGeometry(0,0,0);
		let playerBody = this.createMeshRigidBody(player.meshBody,mass,playerBox,0,0,0);
		playerBody.setActivationState(4);
		playerBody.setAngularFactor(0,1,0);
		//let weaponBody = this.createMeshRigidBody(player.meshWeapon,mass,weaponBox,0,5,0);
	};

The problem now is that I can’t directly modify the player’s position. I have to use physics.
and it’s very easy when you use just one mesh. But the md2 character has three 3d objects.

• a THREE.Object3d that is the root for all models.
• a THREE.MorphBlendMesh for the character body.
• and another THREE.MorphBlendMesh for the player’s weapon.

And when i try to move the body it becomes crazy.

A code modification in the MD2CharacterComplex.js file.

		var scalingFactor = 20;
		
		if (this.usingAmmo) {
			let resultantImpulse = new Ammo.btVector3( Math.sin( this.bodyOrientation ) * forwardDelta, 0, Math.cos( this.bodyOrientation ) * forwardDelta )
			resultantImpulse.op_mul(this.walkSpeed/10);		
			let physicsBody = this.meshBody.userData.physicsBody;
			physicsBody.setLinearVelocity( resultantImpulse );
		}

It doesn’t work

What I want to do is use the original code to move the character.

// this is inside the player movement function in MD2CharacterComplex.js
this.root.position.x += Math.sin( this.bodyOrientation ) * forwardDelta;
this.root.position.z += Math.cos( this.bodyOrientation ) * forwardDelta;
this.root.rotation.y = this.bodyOrientation;

And update the position of the physical body every time the xz position changes.
Then ammo can do the collisions.