These are valid values for Mesh.drawMode, and control how the list of vertices is interpeted once sent to the GPU.
THREE.TrianglesDrawMode
This is the default, and results in every three consecutive vertices (v0, v1, v2), (v2, v3, v5), ... being interpreted as a separate triangle.
If the number of vertices is not a multiple of 3, excess vertices are ignored.
THREE.TriangleStripDrawMode
This will result in a series of triangles connected in a strip, given by (v0, v1, v2), (v2, v1, v3), (v2, v3, v4), ... so that every subsequent triangle shares two vertices with the previous triangle.
THREE.TriangleFanDrawMode
This will result in a series of triangles each sharing the first vertex (like a fan), given by (v0, v1, v2), (v0, v2, v3), (v0, v3, v4), ...
var geometry = new THREE.Geometry();
geometry.vertices.push(
new THREE.Vector3( -10, 10, 0 ),
new THREE.Vector3( -10, -10, 0 ),
new THREE.Vector3( 10, -10, 0 ),
...
);
geometry.faces.push( new THREE.Face3( 0, 1, 2 ), ... );
var material = new THREE.MeshBasicMaterial( { color: 0xffff00 } );
var mesh = new THREE.Mesh( geometry, material );
mesh.drawMode = THREE.TrianglesDrawMode; //default
scene.add( mesh );