//A scenegraph is composed of SceneNodes
public override void LoadContent(ContentManager content, GraphicsDevice g)
{
base.LoadContent(content, g);
//Set up our camera and primitive renderer
cam = new FirstPersonCamera(0.5f, 5f); //0.5f is the turn speed for the camera, and 5f is the translational speed
cam.Pos = new Vector3(3, 3, 13); //Move our camera to the point (3, 3, 13)
primBatch = new PrimitiveBatch(g); //Initialize our PrimitiveBatch
//Define the objects in our scene
Mesh sphere, cylinder, box; //Define the meshes we will use for the robot arm
//A mesh holds a list of vertices, and a list of indices which represent triangles
MeshNode arm, elbow, forearm, wrist, hand; //Define all the parts of the robot arm we will use
MeshBuilder mb = new MeshBuilder(g); //MeshBuilder is a helper class for generating 3D geometry
//It has some built in functions to create primitives, as well as
//functions to create your own arbitrary meshes
//Genererate our geometry
//All geometry created is centered around the origin in its local coordinate system
sphere = mb.CreateSphere(0.5f, 15, 15); //Create a sphere mesh, with radius 0.5 and with 15 subdivisions
cylinder = mb.CreateCylinder(0.3f, 2.0f, 15); //Create a cylinder with radius 0.3, a height of 2, and 15 subdivisions
box = mb.CreateBox(0.8f, 1.4f, 0.1f); //Create a box with width 0.8, height of 1.4, and depth of 0.1
shoulder = new MeshNode(sphere); //Assign the sphere mesh to our shoulder node
arm = new MeshNode(cylinder); //Assign the cylinder mesh to our arm node
arm.SetPos(new Vector3(0, -1, 0)); //Translate the arm down 1 on the y axis
elbow = new MeshNode(sphere); //Assign a sphere to our elbow node
elbow.SetPos(new Vector3(0, -2, 0)); //Translate the elbow down 2 on the y axis
forearm = new MeshNode(cylinder); //Assign a cylinder to our forearm node
forearm.SetPos(new Vector3(0, -1, 0)); //Translate the forearm down 1 on the y axis
wrist = new MeshNode(sphere); //Assign a sphere for the wrist node
wrist.SetPos(new Vector3(0, -2, 0)); //Translate the wrist down 2 on the y axis
hand = new MeshNode(box); //Assign the box to the hand node
hand.SetPos(new Vector3(0, -0.7f, 0)); //Translate the hand down 0.7 (half the height of the box) on the y axis
shoulder.AddChild(arm); //The shoulder is the root of this scene, in our case. It is the parent
shoulder.AddChild(elbow); //of both the arm and the elbow
elbow.AddChild(forearm); //The elbow is the parent of the forearm and wrist
elbow.AddChild(wrist);
wrist.AddChild(hand); //The wrist is the parent of the hand
shoulder.SetPos(new Vector3(0, 5, 0)); //This call effectively translates the entire arm up 5 on the y axis
}