Nothing To Report

Well, there’s not much to report really. I’ve been spreading myself very thin recently, investigating a few different things, so I thought might be nice to post a status update.

Variance Shadow Maps

Yes, I’m jumping on the variance shadow maps boat. They look nice, they’re easy to implement, and have relatively small overhead over traditional shadow maps. I read the article in GPU Gems 3, which is also available here, and it was pretty easy to implement from there. It probably took me about 2 hours to go from no shadows at all to variance shadow maps. After a bit of tomfoolery to get rid of the light-leaking I ended up with the image below. I haven’t implemented any bias yet, so there are some errors there, but the VSMs appear to be working very nicely.

Better Tone Mapping

My current tone mapping algorithm doesn’t look that good, so I’ve been investigating any alternatives. I was initially put off Reinhard tone mapping when I first looked at the DirectX HDRLighting sample a long time ago because it treated each channel completely independently. This is a really nasty idea since it can change the hue of the image during tone mapping as each channel gets compressed by a different amount. I recently re-read a gamedev article and then implemented Reinhard’s tone mapping using based on the pixel luminance, which gave much nicer results, and didn’t change the hue. One note on that article though: It says that to convert to RGB from the final luminance you need to multiply by the luminance, which doesn’t seem right. What I did was to divide by the old luminance and then multiply by the tone mapped luminance. It’s hard to tell right now if it looks better or worse, it’s just different.

The image above is using this new tone mapping, but I’m not doing the dynamic image key calculation at the moment. That basically gives me three variables (image key, midzone luminance, and white luminance) which aren’t very intuitive to tweak. I’ve generally been leaving the midzone gray at 0.18 as suggested, and then tweaking the image key and white luminance to get something that looks OK.

Windows Presentation Foundation

I’ve spent a lot of time at work recently improving one of our C# tools, which is Windows Forms based. There are many things I dislike about Windows Forms, like the lack of built-in support for something useful like the command-pattern, the horrible input handling, menu shortcuts, you name it! For my own education, last weekend I started reading about the latest and greatest from Microsoft: The Windows Presentation Foundation. From my brief foray into WPF, it seems that a lot of the the things in Windows Forms that I’ve spent time trying to fix or circumvent appear to have been addressed.

For example, in Windows Forms, if you don’t handle a key-press event in a control, then no-one else gets to handle it either, unless they have specifically attached an event handler to that controls key-press event. In WPF they have the notion of tunneling and bubbling commands. This basically means that if you don’t handle that event then your parent gets a chance to handle it (it bubbles up), and vice-versa for tunneling events.

There seems to be a much greater emphasis of splitting the View from the Model (in the Model-View-Controller sense that is), with only very loose references (or none at all) required to bind everything together. I’m very interested in finding a good method for splitting the View code from the Controller and Model code, so I’ve been reading a few articles, some of which you can read here: Model-View-Controller, Model-View-ViewModel, Presentation Model. I really liked Martin Fowler’s description of Presentation Model in particular. The Model-View-ViewModel paper was also a good read, but I really dislike the resuse of the words Model and View in the terminology (it’s doubly confusing since I already have C++ classes called Model and View representing a 3D model and a view point respectively). In Windows Forms you seem to be almost forced to keep your View and Controller code tightly bound, but there appears to be much more freedom in WPF.

I also bought a book about WPF by some bloke from Microsoft called Adam Nathan, which so far has been some good reading (despite the liberal sprinkling of exclamation marks on every page). I’d love to see a book that combines WPF and something like Model-View-ViewModel to create a real-world, complicated application rather than the fairly simple examples that appear in books and online articles. If anyone knows of a book like this, then please let me know!

Oh, but it’s not all roses in WPF though. One of the first videos I watched was this one. If you’ve seen it, then you probably have the same same thought running around your head that that I did when I first watched it: WTF? You’re basically allowed to reuse some storage from a dependency property that isn’t used to affect your control. For example, assuming you’re not parented to a DockPanel, you can use something like DockPanel.Width to store an arbitrary number. It’s like the Tag in Windows Forms, but much much worse. Microsoft seem to be touting it like a really cool feature, when it feels more like a dirty hack to me. Using unused properties to store arbitrary data is a really quick way to make your code unmaintainable as far as I’m concerned. I don’t want to have to search the code for where someone put the data into the property in order to work out what it is actually storing… Urgh!

Articles

Yeah, I’m about 80% through writing one about storing function call arguments in MockItNow at the moment. It’ll be up as soon as I finish the last 80%. That’s all!