/// <summary>Updates the reflected image on the water surface</summary>
/// <param name="gameTime">Snapshot of the game's timing values</param>
/// <param name="camera">Camera through which the scene is being viewed</param>
/// <param name="reflectedSceneDrawer">
/// Delegate that will be called to draw the scene in its reflected state
/// </param>
/// <remarks>
/// <para>
/// When the delegate is called, the scene should be drawn normally using
/// the provided game time and camera. The view matrix of the provided camera
/// will have been adjusted to draw the scene upside-down and the graphics device
/// will be configured to clip off anything that's below the water surface.
/// </para>
/// <para>
/// Some adjustments can be made, like rendering the reflection with reduced
/// detail, cheaper effects or even leaving our parts of the scene to improve
/// performance since the reflection will not be clearly displayed anyway.
/// </para>
/// </remarks>
public void UpdateReflection(
GameTime gameTime, Camera camera, SceneDrawDelegate reflectedSceneDrawer
)
{
// Create a matrix that undoes the view and projection transforms. We don't
// involve any world matrix here because the water plane exists in
// the world coordinate frame, its world matrix is always the identity matrix.
Matrix viewProjection = camera.View * camera.Projection;
Matrix inverseViewProjection = Matrix.Invert(viewProjection);
// The water plane in world coordinates. We want to clip away everything that's
// below the water surface (as only things above it should be reflected)
Vector4 worldWaterPlane = new Vector4(Vector3.Down, 0.0f);
// The water plane as sent through the inverse view and projection transforms.
// This is neccessary because the plane will be transformed by those two
// matrices when it is applied to the scene. Don't ask me why.
Vector4 projectedWaterPlane = Vector4.Transform(
worldWaterPlane, Matrix.Transpose(inverseViewProjection)
);
#if XNA_4
this.graphicsDevice.SetRenderTarget(this.reflectionRenderTarget);
#else
this.graphicsDevice.SetRenderTarget(0, this.reflectionRenderTarget);
#endif
try {
// Set up a clipping plane that only draws those parts of the scene that
// are above the water because that's the only thing we want to appear in
// the reflection on the water surface.
#if !XNA_4 // TODO: Move this to the shader for both XNA 3.1 and XNA 4.0
this.graphicsDevice.ClipPlanes[0].Plane = new Plane(projectedWaterPlane);
this.graphicsDevice.ClipPlanes[0].IsEnabled = true;
try {
#endif
Matrix reflectionMatrix = Matrix.CreateReflection(new Plane(worldWaterPlane));
this.reflectionCamera.View = reflectionMatrix * camera.View;
this.reflectionCamera.Projection = camera.Projection;
reflectedSceneDrawer(gameTime, this.reflectionCamera);
#if !XNA_4
}
finally {
this.graphicsDevice.ClipPlanes[0].IsEnabled = false;
}
#endif
}
finally {
#if XNA_4
this.graphicsDevice.SetRenderTarget(null);
#else
this.graphicsDevice.SetRenderTarget(0, null);
this.reflectionTexture = reflectionRenderTarget.GetTexture();
#endif
}
}
/// <summary>Updates the reflected image on the water surface</summary>
/// <param name="gameTime">Snapshot of the game's timing values</param>
/// <param name="camera">Camera through which the scene is being viewed</param>
/// <param name="reflectedSceneDrawer">
/// Delegate that will be called to draw the scene in its reflected state
/// </param>
/// <remarks>
/// <para>
/// When the delegate is called, the scene should be drawn normally using
/// the provided game time and camera. The view matrix of the provided camera
/// will have been adjusted to draw the scene upside-down and the graphics device
/// will be configured to clip off anything that's below the water surface.
/// </para>
/// <para>
/// Some adjustments can be made, like rendering the reflection with reduced
/// detail, cheaper effects or even leaving our parts of the scene to improve
/// performance since the reflection will not be clearly displayed anyway.
/// </para>
/// </remarks>
public void UpdateReflection(
GameTime gameTime, Camera camera, SceneDrawDelegate reflectedSceneDrawer
) {
// Create a matrix that undoes the view and projection transforms. We don't
// involve any world matrix here because the water plane exists in
// the world coordinate frame, its world matrix is always the identity matrix.
Matrix viewProjection = camera.View * camera.Projection;
Matrix inverseViewProjection = Matrix.Invert(viewProjection);
// The water plane in world coordinates. We want to clip away everything that's
// below the water surface (as only things above it should be reflected)
Vector4 worldWaterPlane = new Vector4(Vector3.Down, 0.0f);
// The water plane as sent through the inverse view and projection transforms.
// This is neccessary because the plane will be transformed by those two
// matrices when it is applied to the scene. Don't ask me why.
Vector4 projectedWaterPlane = Vector4.Transform(
worldWaterPlane, Matrix.Transpose(inverseViewProjection)
);
#if XNA_4
this.graphicsDevice.SetRenderTarget(this.reflectionRenderTarget);
#else
this.graphicsDevice.SetRenderTarget(0, this.reflectionRenderTarget);
#endif
try {
// Set up a clipping plane that only draws those parts of the scene that
// are above the water because that's the only thing we want to appear in
// the reflection on the water surface.
#if !XNA_4 // TODO: Move this to the shader for both XNA 3.1 and XNA 4.0
this.graphicsDevice.ClipPlanes[0].Plane = new Plane(projectedWaterPlane);
this.graphicsDevice.ClipPlanes[0].IsEnabled = true;
try {
#endif
Matrix reflectionMatrix = Matrix.CreateReflection(new Plane(worldWaterPlane));
this.reflectionCamera.View = reflectionMatrix * camera.View;
this.reflectionCamera.Projection = camera.Projection;
reflectedSceneDrawer(gameTime, this.reflectionCamera);
#if !XNA_4
}
finally {
this.graphicsDevice.ClipPlanes[0].IsEnabled = false;
}
#endif
}
finally {
#if XNA_4
this.graphicsDevice.SetRenderTarget(null);
#else
this.graphicsDevice.SetRenderTarget(0, null);
this.reflectionTexture = reflectionRenderTarget.GetTexture();
#endif
}
}
