Last time I talked about using timers for scheduling events by simply keeping track of a time limit and how much time elapsed. Another good use for timers is performing some action over time, such as modifying alpha to fade an object in or out, or sliding an object from one location to another. Let’s use the fading example. Fading is often done by animating transparency. The object starts out completely transparent, and gradually becomes less transparent until it’s fully…
It’s going on seven months since my last post, which is kind of pathetic. When finishing a large project, like the WP7 port of Guardian, my brain tends to shut down for awhile for recharging. That, on top of starting a new job back in November, lead to a much longer blogging hiatus than intended. So, how about something simple to get back into the swing of things. And since we’re talking about time… Very often in video games there…
I’ve been working on a Windows Phone 7 port of Guardian and finally have something to show for it. All of the systems are in place now, just need to do a lot of tuning and game play tweaking. Of course, at this point I have no idea how it’s going to perform on an actual phone, but it should do fairly well. Hopefully there won’t be too much optimization required after I get my hands on some hardware. I…
By default (at least on my computer, running Windows 7), CLR Profiler 2 won’t work with new XNA apps since they utilize the new .NET framework. It looks like it’s working when you try it, but when it shows the final statistics window it’s empty. Fortunately, it’s possible to enable support using the new profiler compatibility settings functionality, which for this case involves simply setting the COMPLUS_ProfAPI_ProfilerCompatibilitySetting environment variable before running CLR Profiler.
I’ve had a couple of questions about what changes are needed to get the texture modification tutorial to work in XNA 3.1. So, here’s a 3.1 version of the project, and a quick overview of the major things that need to change. You need to create the depth/stencil buffer yourself, set it on the GraphicsDevice when setting the render target, and restore the previous buffer when you’re done. RenderTarget2D can’t be used directly as a texture, you must call RenderTarget2D.GetTexture…
In the tutorial recently posted, I created the render state objects using some old-school syntax.
[csharp]
StencilAlways = new DepthStencilState();
StencilAlways.StencilEnable = true;
StencilAlways.StencilFunction = CompareFunction.Always;
StencilAlways.StencilPass = StencilOperation.Replace;
StencilAlways.ReferenceStencil = 1;
StencilAlways.DepthBufferEnable = false;
[/csharp]
You can do this in a much better way nowadays.
[csharp]
StencilAlways = new DepthStencilState()
{
StencilEnable = true,
StencilFunction = CompareFunction.Always,
StencilPass = StencilOperation.Replace,
ReferenceStencil = 1,
DepthBufferEnable = false
};
I’ve seen this syntax before, but 20 years of habits die hard and I rarely remember to use it. Hopefully it will stick now, and make my crappy code that much less crappy.
[/csharp]
Sometimes you need to modify a texture while your game is running, and there are a number of ways to do this. One of the first things newer game programmers often try to do is use Texture2D.GetData to copy the texture data from the GPU to an array on the CPU, modify the bytes, and then send it back to the GPU with Texture2D.SetData.
This is a bad idea on many, levels. Beyond issues with pipeline stalls, GetData and SetData can be slow, especially when working with a large texture. Any time you’re tempted grab data from the GPU for use on the CPU you should very carefully consider all of your options. There are often other solutions that let you keep the data entirely on the GPU and accomplish the same thing.
This tutorial will use an example that could be solved with GetData and SetData, and show you another alternative using render targets and the stencil buffer that will let you perform the same function entirely on the GPU.
When developing the iPhone version of Guardian I manually created my sprite sheets. I used individual sprites up until the end so everything was pretty much set in stone by the time I created the the sprite sheet. Even then I ended up having to recreate the sprite sheet two or three times, and let me tell you, manually figuring out the texture coordinates isn’t a particularly pleasant experience. In this case I believe I made the right choice. There were few enough sprites that I would have spent more time creating the tool than I would have saved.
Someone over in the XNA forums asked a question about how to make sprite explosions like those in the old Defender arcade game, where the sprite is broken into pieces and exploded everywhere.
So we finally come to the last post in the horizon culling series. Previously we’ve discussed what horizon culling is and some reasons for using it. Then we went through the math involved in determining the angle between a line from the camera to the planet center and a line from the center to the point on the horizon.