I'm making my first 3D-game with XNA (MonoGame) and have come to a point where I wish to add a crosshair for the player. To do this I need the on-screen coordinates of the location where my fighter would actually fire. However, I've run into some problems with this, mainly in finding my world matrix...

When drawing, I use the following snippet:

foreach (ModelMesh mesh in model.Meshes)
        {
            foreach (BasicEffect effect in mesh.Effects)
            {
                effect.EnableDefaultLighting();

                effect.World = transforms[mesh.ParentBone.Index]
                     * Matrix.CreateRotationX(angle.X)
                     * Matrix.CreateRotationY(angle.Y)
                     * Matrix.CreateRotationZ(angle.Z)
                     * Matrix.CreateTranslation(Position);

                effect.View = camera.ViewMatrix;

                effect.Projection = camera.Projection;
            }
            mesh.Draw();
        }

My understanding is that to be able to get my 2D screen coordinates, I need to use something like this:

//Yes, this currently returns a Vector3 and probably looks horrible on line 2 but I have not yet had any ouput to test this with
Vector3 temp = Game1.game.GraphicsDevice.Viewport.Unproject(Fighter.player.Position + Fighter.player.Forward * 50, Camera3D.camera.Projection, Camera3D.camera.ViewMatrix, Matrix.Identity);
Position = new Vector2(temp.X, temp.Y);

Which requires the world transform as the final argument. Since my effect.world changes with each BasicEffect (7 of them) I can't really get a hold on what my World Matrix is.

Any help?

I'm making my first 3D-game with XNA (MonoGame) and have come to a point where I wish to add a crosshair for the player. To do this I need the on-screen coordinates of the location where my fighter would actually fire. However, I've run into some problems with this, mainly in finding my world matrix...

When drawing, I use the following snippet:

foreach (ModelMesh mesh in model.Meshes)
        {
            foreach (BasicEffect effect in mesh.Effects)
            {
                effect.EnableDefaultLighting();

                effect.World = transforms[mesh.ParentBone.Index]
                     * Matrix.CreateRotationX(angle.X)
                     * Matrix.CreateRotationY(angle.Y)
                     * Matrix.CreateRotationZ(angle.Z)
                     * Matrix.CreateTranslation(Position);

                effect.View = camera.ViewMatrix;

                effect.Projection = camera.Projection;
            }
            mesh.Draw();
        }

My understanding is that to be able to get my 2D screen coordinates, I need to use something like this:

//Yes, this currently returns a Vector3 and probably looks horrible on line 2 but I have not yet had any ouput to test this with
Vector3 temp = Game1.game.GraphicsDevice.Viewport.Unproject(Fighter.player.Position + Fighter.player.Forward * 50, Camera3D.camera.Projection, Camera3D.camera.ViewMatrix, Matrix.Identity);
Position = new Vector2(temp.X, temp.Y);

Which requires the world transform as the final argument. Since my effect.world changes with each BasicEffect (7 of them) I can't really get a hold on what my World Matrix is.

Any help?

EDIT

In my case I was able to use the code I used above with the only change that instead of Viewport.Unproject I used Viewport.Project.

I'm still not sure how to get the world matrix when it's set with variables that can vary (such as transforms[mesh.ParentBone.Index]) and am still intrested in this. My specific problem however was solvable by simply using Matrix.Identity as world matrix.