3D

This guide will show you how to draw 3D geometry that lines up with the 2D layers.

This guide builds on top of Depth.

View and projection

GetView3D() and GetProjection3D() give you a perspective view of the same world. A point at (x, y) on the layer at depth z is at (x, y, z) in 3D, so you can mix 2D layers with 3D geometry:

_effect = new BasicEffect(GraphicsDevice) {
    VertexColorEnabled = true,
};

_camera.SetViewport();

_effect.World = Matrix.Identity;
_effect.View = _camera.GetView3D();
_effect.Projection = _camera.GetProjection3D();

foreach (EffectPass pass in _effect.CurrentTechnique.Passes) {
    pass.Apply();
    GraphicsDevice.DrawUserPrimitives(PrimitiveType.TriangleList, _vertices, 0, _vertices.Length / 3);
}

_camera.ResetViewport();

The position, Rotation, Scale and FocalLength all apply to the 3D view. Here, the colored squares on top are drawn on the ground with View and the dark ones under them on a layer at -0.5 with GetView(-0.5f). The walls in between are 3D triangles that go from a depth of 0 to -0.5:

The y axis points down like in 2D and z points toward the camera. A model made for a world where y points up comes out mirrored, which also flips which side of its triangles gets culled. You can use RasterizerState.CullNone if that’s an issue.

Near and far planes

GetProjection3D takes the distance of the near and far planes from the camera. They’re at 0.01 and 100 by default. Geometry that’s outside of that range doesn’t get drawn:

_effect.Projection = _camera.GetProjection3D(0.1f, 1000f);

GetBoundingFrustum3D takes the same distances and gives you the 3D frustum, for culling:

BoundingFrustum frustum = _camera.GetBoundingFrustum3D();
if (frustum.Intersects(model.Bounds)) {
    // Draw the model.
}

Orthographic projection

GetProjection() is the projection that goes with GetView(z). It’s useful for effects that take the view and the projection separately, like a BasicEffect that draws on one of the layers:

_effect.View = _camera.GetView(-1f);
_effect.Projection = _camera.GetProjection();