Examples: include example code of importing a HCAD convex hull from a GLTF file

Hello, Thanks for maintaining cannon!

I have an error when I create ConvexPolyhedron, I must miss something

I have a few errors when creating a ConvexPolyhedron Body : cannon-es.js:2247 .faceNormals[0] = Vec3(0,0,-0.9999999999999999) looks like it points into the shape? The vertices follow. Make sure they are ordered CCW around the normal, using the right-hand rule.

My process :

• Loading a mesh with a buffer geometry from an HCAD convex decomposition
• I retrieve the faces & vertex to create the cannon body

Code :

CreateConvexPolyhedron(geometry, scaleVec) {
        if (!geometry.vertices) {
            geometry = new THREE.Geometry()
                .fromBufferGeometry(geometry)
                .scale(scaleVec.x, scaleVec.y, scaleVec.z)
            geometry.mergeVertices()
            geometry.computeBoundingSphere()
            geometry.computeFaceNormals()
        }
        const points = [],
            faces = []
        points = geometry.vertices.map(function (v) {
            return new CANNON.Vec3(v.x, v.y, v.z)
        })

        faces = geometry.faces.map(function (f) {
            return [f.a, f.b, f.c]
        })
        return new CANNON.ConvexPolyhedron({ vertices: points, faces })
    }

Help would be more than welcome 😃

Thanks

[felixmariotto]

I’ve got this bug with the generated body though, do you think it’s related to the way I’m making the convex polyhedron ? Bodies constructed from primitives behave normally ( they don’t jump wildly when colliding ). In this scene the sphere, the box and the convex polyhedron have a mass of 1 and use the same material.

https://user-images.githubusercontent.com/46470486/107856840-4b3efb80-6e2b-11eb-8bd9-6de604ac52db.mp4

[felixmariotto]

@marcofugaro

I came up with this :

const hullBody = new CANNON.Body({
	mass,
	material
});

glb.scene.traverse( (obj) => {

	if ( obj.geometry ) {

		const posAttrib = obj.geometry.attributes.position;
		const vertices = [];

		for ( let i=0 ; i<posAttrib.count ; i++ ) {

			vertices.push(
				new CANNON.Vec3(
					posAttrib.getX( i ),
					posAttrib.getY( i ),
					posAttrib.getZ( i )
				)
			);

		}

		//

		const normAttrib = obj.geometry.attributes.normal;
		const normals = [];

		for ( let i=0 ; i<normAttrib.count ; i++ ) {

			normals.push(
				new CANNON.Vec3(
					normAttrib.getX( i ),
					normAttrib.getY( i ),
					normAttrib.getZ( i )
				)
			);

		}

		//

		const index = obj.geometry.index;
		const faces = [];

		for ( let i=0 ; i<index.count ; i+=3 ) {

			faces.push([
				index.array[ i ],
				index.array[ i + 1 ],
				index.array[ i + 2 ]
			]);

		}

		// Construct polyhedron

		const hullPart = new CANNON.ConvexPolyhedron({ vertices, faces, normals })

		// Add to compound

		hullBody.addShape( hullPart );

	}

});

No idea if it’s optimal, I’m just starting with cannon.js. Thank you for maintaining this fork btw !