Project overhaul

Well, I’ve gotten to the point where I’m satisfied enough with my engine to get some actual game coding done. There are still issues related to shadow rendering but those can be worked on alongside everything else. Right now I’m taking a look at everything from a top-down view and planning to trim down the engine to a leaner size. I will talk more about my game project in a later post… just don’t expect it to be groundbreaking or anything like that 😛

For the sake of completion, I don’t want to get carried away with a one-size-does-all engine that has more than what I truly need. This has been an ongoing learning project lasting over two months, and I feel like it’s come pretty far. The engine isn’t immensely huge- I am focusing on a lightweight design- but now that I’ve worked on it for this long, I have gotten a better idea of what works for my upcoming game, and what I can take out so I don’t wind up with something too big and general-purpose.

The rendering library

The biggest change I made in the past week or so is moving all the rendering code into its own library project. It can finally be considered something of an engine, or at the least, a rendering library. For so long I had just a MeteorEngineDemo project, which is the “game” that uses the renderer, and MeteorEngineDemo.Content which grouped all the effect files from the renderer, and meshes used by the game. Having looked at other open-source projects focused on rendering engines in the past, I knew that this wasn’t going to work in the long run. This is just modular programming 101 here. The effects and rendering logic are part of the engine and irrelevant to whatever content you’ll use for any program, and I gotta follow the DRY principle.

After moving the rendering code into its own project, I now have a library project called MeteorEngine, which is referenced by the MeteorEngineDemo, and the library in turn references MeteorEngine.Content. That last one contains all the content that the engine needs to use (effect files, special meshes, etc). That way, all the content can be compiled and added automatically into a separate content folder that’s used by the MeteorEngine.dll at runtime. These projects will probably be renamed from “MeteorEngine” to “MeteorRenderer” since I’m not concerned with building something that handles all sorts of game logic, and to make it clear that it’s for graphics only.

Now my workflow is greatly improved- I can add a reference to this library with any other project I’m working on, while still being able to update the library’s source, and all the updates are reflected in all the other projects referencing it. Of course, this leads to the downside of making sure that all the code in my projects will still work with the library, but I’m doing a fairly good job in separating the rendering logic from everything else.

Variance shadow mapping didn’t prove flexible enough for my needs so I rolled back to using a standard shadow mapping technique in orthogonal space. The shadow is manually filtered thanks to some code from XNA Info. Also, the renderer now uses two HdrBlendable render targets, one for light accumulation, and the second one is for compositing the completed image (before post-processing). These gave me a bit of trouble, since they require a Point filter and they threw off my texture sampling states, causing crashes on startup or textures to display incorrectly. To my surprise, they didn’t seem to impact the rendering performance a whole lot. As an added bonus, I also switched to using the Nuclex font importer for drawing better-looking SpriteFonts.

Performance

So you’re curious to know how well it does, huh? Well, here’s a quick overview of my specs. My home/testing computer, which has a Radeon HD 4670 series video card, an Intel Core 2 Duo E4500 with 3 GB of ram. So it’s nothing close to being mindblowing and probably somewhere in the mid-range as far as video specs go. I also have a Macbook but unfortunately I can only use the Reach profile on there :-/

Okay, so this pic isn’t HD resolution, but check out dat framerate:

Don’t mind the zero triangle count in the readout- I gotta fix that soon. Since it’s light pre-pass, geometry is rendered at least twice. Three times actually, to project the shadow mapping. Post-effects added are FXAA, depth of field, and light bloom in that order.

At 720p it’s still a respectable framerate at 124fps, but with the effects disabled and switched to deferred rendering mode. With effects enabled, it hovers just below 80fps.

Rendering an entire Sponza model is slower- between 65 and 70 fps with one 2048 x 2048 shadow render target. This is mostly to do with the fact that it requires a lot more draw calls-  the model is made up of almost 400 different meshes, and culling each brute force also takes time. It may be more efficient to render if I merged some of the smaller meshes together and re-export the model, but I’d rather move on and create my own models.

Cutting down the code to size

My design for this library just didn’t spring up from the moment I started. Over a year ago, when I was learning from tutorials on DirectX, I came up with a low-level design for a rendering system. I drew it on a sheet of paper, emphasizing the most important connections with the components (sheet coming later!).

The diagram includes some non-rendering components, the game state management (the AppState and Statemanager), which I added to better visualize how it integrates with the whole program. I also got too carried away with static classes, which are probably not necessary for the design. But this is the basis of the design for my current rendering engine, and now that I look back on it, I want to reduce it down to these bare components.

Some of these components will differ from the original design. Effects will be part of a SceneRenderer class, not the Scene class. The entry point of the renderer (Display) will only exist to load up the SceneRenderer and RenderProfiles, and plug in Scenes and Cameras to it. Also, I won’t even need anything like a ResourceMaker in XNA, because the ContentManager and content pipeline take care of everything in there.

To this end, there will also be a clearer separation of data and data processors. I already have this in place with Scenes and SceneRenderers, as the Scenes are just containers for lights and models. This allows me to make some further refinements to the code:

  • Separation of data and its processing systems
  • Changing data objects from reference types to value types wherever possible (on the other hand, it makes little sense to have value type objects that contain reference types)
  • Reducing allocation of memory as per one of the paths to minimize garbage collection. This would include, for example, less resizing of lists for meshes, visible instances, etc. A lot of this makes more sense on Xbox 360, which I don’t have, so unfortunately I can’t really test this to the fullest.
  • Condensing some related objects to a single, but still manageable system. For my game, I’m set on what specific rendering systems to use, so I could trade away some flexibility for more simplicity.

Experimenting with more advanced HLSL is also an option. With classes fully supported in Shader Model 3.0 and XNA as confirmed by this forum post, it can make things more interesting for creating shader frameworks based around deferred rendering. With them we have more ways to manage reusable code and abstraction in shader functions. Here’s a really good article thats shows how function pointer behavior can be done- fully compatible with Shader Model 3.0! To those not used to OOP in HLSL it’s a big eye opener in designing shader code.

So now that it seems like I’m on the final stretch of working on this as a standalone project, it’s time to battle-test it. I already made another project which will be the “new version” of my game, and threw in my rendering library along with it. The screenshots you saw above are taken from that project. For now it’s going to be a matter of adding my own content and whatever game code I could reuse from the old project. As I’m working on my game, the rendering library will also keep changing along the way.

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