Hi guys,

I want to lay a 2D Rectangle at the same position where my 3D model is (x and y coordinates).

My problem is following:

I can't use the x and y coordinates of my model, because it's relativ to the camera.
The coordinates of the rectangle refer to the screen resolution.

I will use the rectangle to detect collisions with my 2D landscape.

Has anyone a hint for me?

Either drawing BoundingBoxes in 3D or use Viewport.Project to project your models 3D world space position into screen space. Heres an example using the 2nd method.

Hi, i tried this... but is there a way to use this with the standartcamera?

If I try this, i get a negative X and Y-Coordinate

protected override void Update(GameTime gameTime)
        {

            // Create a total bounding sphere for the mesh
            BoundingSphere totalbounds = new BoundingSphere();
            foreach (ModelMesh mesh in player.model.Meshes)
            {
                totalbounds = BoundingSphere.CreateMerged(totalbounds, mesh.BoundingSphere);
            }

            // Project the center of the 3D object to the screen, and center the
            // sprite there
            Vector3 center = GraphicsDevice.Viewport.Project(totalbounds.Center,
                cameraProjectionMatrix, cameraViewMatrix, Matrix.Identity);
            player.boundingRectangle.X = (int)center.X;
            player.boundingRectangle.Y = (int)center.Y;

            // Create a bounding box from the bounding sphere, and find the corner
            // that is farthest away from the center using Project
            BoundingBox extents = BoundingBox.CreateFromSphere(totalbounds);
            float maxdistance = 0;
            float distance;
            Vector3 screencorner;
            foreach (Vector3 corner in extents.GetCorners())
            {
                screencorner = GraphicsDevice.Viewport.Project(corner,
                cameraProjectionMatrix, cameraViewMatrix, Matrix.Identity);
                distance = Vector3.Distance(screencorner, center);
                if (distance > maxdistance)
                    maxdistance = distance;
            }


           



            UpdateMouse();
            UpdateMovement();
            
            base.Update(gameTime);
        }

Thanks for helping,
Robin

jadephoenix1988:

Hi, i tried this... but is there a way to use this with the standartcamera?

If I try this, i get a negative X and Y-Coordinate

What is 'the standartcamera'?

What is the X and Y Coordinate - is it player.boundingRectangle.X and Y?

By if standard camera you mean View and Projection matricies, yea, you can do it...

// This is a scale factor that depends on a lot of things, use guess and check to get it just right
const Single SOMEFACTOR = 1f;

// Transform the object's location to 2D space
Vector4 ScreenPosition = Vector4.Transform(ObjectLocation, View * Projection);

// Ok, now we need to get a representation of how "large" this object appears on our screen...
Single Radius =  Projection.M11 * ScreenDimensions.Y / ScreenPosition.W;

// Ok, now we know how far this object extends from ScreenPosition.X, ScreenPosition.Y but our would might be scaled differently
Radius = Radius * SOMEFACTOR;

Hi andorov!

If I use Vector4.Transform, I get a x-coordinate with the value 0 and y with 36.... but the "movement" of my boundingrect is like the movement of the mesh... I'll try to find the fault!

greetz,
Robin

Hey :-)! It worked with project() :)))