Dynamic Environmental Reflections in Direct3D 11 and C#

Last time, we looked at using cube maps to render a skybox around our 3D scenes, and also how to use that sky cubemap to render some environmental reflections onto our scene objects.  While this method of rendering reflections is relatively cheap, performance-wise and can give an additional touch of realism to background geometry, it has some serious limitations if you look at it too closely.  For one, none of our local scene geometry is captured in the sky cubemap, so, for instance, you can look at our reflective skull in the center and see the reflections of the distant mountains, which should be occluded by the surrounding columns.  This deficiency can be overlooked for minor details, or for surfaces with low reflectivity, but it really sticks out if you have a large, highly reflective surface.  Additionally, because we are using the same cubemap for all objects, the reflections at any object in our scene are not totally accurate, as our cubemap sampling technique does not differentiate on the position of the environment mapped object in the scene.

The solution to these issues is to render a cube map, at runtime, for each reflective object using Direct3D.  By rendering the cubemap for each object on the fly, we can incorporate all of the visible scene details, (characters, geometry, particle effects, etc) in the reflection, which looks much more realistic.  This is, of course, at the cost of the additional overhead involved in rendering these additional cubemaps each frame, as we have to effectively render the whole scene six times for each object that requires dynamic reflections.

This example is based on the second portion of Chapter 17 of Frank Luna’s Introduction to 3D Game Programming with Direct3D 11.0, with the code ported to C# and SlimDX from the native C++ used in the original example.  You can download the full source for this example from my GitHub repository, at https://github.com/ericrrichards/dx11.git, under the DynamicCubeMap project.

A Look-At Camera in SlimDX and Direct3D 11

Today, we are going to reprise our Camera class from the Camera Demo.  In addition to the FPS-style camera that we have already implemented, we will create a Look-At camera, a camera that remains focused on a point and pans around its target.  This camera will be similar to the very basic camera we implemented for our initial examples (see the Colored Cube Demo).  While our FPS camera is ideal for first-person type views, the Look-At camera can be used for third-person views, or the “birds-eye” view common in city-builder and strategy games.  As part of this process, we will abstract out the common functionality that all cameras will share from our FPS camera into an abstract base camera class.

The inspiration for this example come both from Mr. Luna’s Camera Demo (Chapter 14 of Frank Luna’s Introduction to 3D Game Programming with Direct3D 11.0), and the camera implemented in Chapter 5 of Carl Granberg’s Programming an RTS Game with Direct3D.  You can download the full source for this example from my GitHub repository at https://github.com/ericrrichards/dx11.git under the CameraDemo project.  To switch between the FPS and Look-At camera, use the F(ps) and L(ook-at) keys on your keyboard.

An FPS Camera in SlimDX

Up until now, we have been using a fixed, orbiting camera to view our demo applications.  This style of camera works adequately for our purposes, but for a real game project, you would probably want a more flexible type of camera implementation.  Additionally, thus far we have been including our camera-specific code directly in our main application classes, which, again, works, but does not scale well to a real game application.  Therefore, we will be splitting out our camera-related code out into a new class (Camera.cs) that we will add to our Core library.  This example maps to the CameraDemo example from Chapter 14 of Frank Luna’s Introduction to 3D Game Programming with Direct3D 11.0.  The full code for this example can be downloaded from my GitHub repository, https://github.com/ericrrichards/dx11.git, under the CameraDemo project.

We will be implementing a traditional First-Person style camera, as one sees in many FPS’s and RPG games.  Conceptually, we can think of this style of camera as consisting of a position in our 3D world, typically located as the position of the eyes of the player character, along with a vector frame-of-reference, which defines the direction the character is looking.  In most cases, this camera is constrained to only rotate about its X and Y axes, thus we can pitch up and down, or yaw left and right.  For some applications, such as a space or aircraft simulation, you would also want to support rotation on the Z (roll) axis.  Our camera will support two degrees of motion; back and forward in the direction of our camera’s local Z (Look) axis, and left and right strafing along our local X (Right) axis.  Depending on your game type, you might also want to implement methods to move the camera up and down on its local Y axis, for instance for jumping, or climbing ladders.  For now, we are not going to implement any collision detection with our 3D objects; our camera will operate very similarly to the Half-Life or Quake camera when using the noclip cheat.

Our camera class will additionally manage its view and projection matrices, as well as storing information that we can use to extract the view frustum.  Below is a screenshot of our scene rendered using the viewpoint of our Camera class (This scene is the same as our scene from the LitSkull Demo, with textures applied to the shapes).