Fast Alpha-Blending In Your GUI

visnu writes: "I've been waiting for this for 2 years now -- a REAL glass-like windowing system. And yes, it's Microsoft to do it. Ever since W2k came out, and they included alpha-blending in the GDI, I was tempted to write a little tool to turn on any window's transparency, but of course I'm way too lazy to do that. These guys weren't though: glass2k runs in the systray and handles turning on any window's transparency. yes, here's a screenshot. I'm not too sure about the speed in W2k, but in XP w/ the newest Nvidia drivers and a somewhat recent video card, it's hardware accelerated, and yes, you should be drooling." Update: 11/26 19:00 GMT by T : Links updated, so hopefully you'll be able to actually get to the content again :)

Comments

Nothing new

[Mwongozi]

Stardock have an application called WindowsFX which allows you to turn on transparent windows selectively, for example, just for Notepad windows, which is much less of a CPU hit than turning it on for everything. It also lets you add shadows and various other graphical trickery to windows.

It's rather cool, but not free, in either sense of the word.

Ho Hum, Already Done

[under_score]

Over a decade ago in the NeXT computers. Transparency (alpha-channel) was part of their graphics system (including their windowing system built using Display Postscript), pretty much from day one. I wrote software which depended on it - some funky drag-n-drop stuff which used transparency in icons. It was fast back then on a 25MHz 68040 - eighty times slower clock speed than todays high end processors!!!

Transparency effect...

[frleong]

It's very easy, suppose that hwnd is your window handle:

SetWindowLong(hwnd, GWL_EXSTYLE, GetWindowLong(hwnd, GWL_EXSTYLE) | WS_EX_LAYERED); SetLayeredWindowAttributes (hwnd, 0, 180, LWA_ALPHA);

GUI programming in Windows is quite snappy.

Does anyone here get the point?

[Dynedain]

Sure, this stuff has been done before on other operating systems. Sure, Win2k has had it hidden in the API. THE POINT IS that this is being done by your GRAPHICS CARD....nothing on the processor end. Oh, and its a 54K yes 54K download, and is easy to use. Calm down people. Why start flaming someone without ever checking out what it is?

also HW acc on win2k + Radeon + 3276drv

[Otis_INF]

I just installed it on my Win2k box with ATi Radeon 32MB DDR and v3276 drivers and it runs very smooth, the windows are draggable with content at full speed on 1600x1200x32bpp. A year ago, some registry hacking tool did this too, but then all drivers were software rendering the alphablended windows and it was dogslow. However making Internet Explorer semi transparent isn't that fast. I guess (but do not know for sure) IE is redrawing the complete page every time something changes in the window (like typing in an edit box).

Alpha Blended Pie Menus and Censorship in The Sims

[SimHacker]

The classic papers on transparent user interfaces include Toolglass and Magic Lenses: The See-Through Interface (1993), and A Taxonomy of See-Through Tools (1994).

The pie menus in The Sims use a combination of desaturation, darkening, and alpha blending to feather the edges of the menu.

Why transparency and the other effects? I didn't want the pie menus to obscure too much of the scene behind them. You can see through the pie menu as the animation continues on in real time behind it. The head of the currently selected person is drawn in the center of the pie menu, and follows the cursor by looking at the currently selected item.

I found it necessary to somehow separate the head from the rest of the scene, otherwise it looked like a giant head was floating in a room of the house! Drawing a solid opaque menu background would obscure too much of the scene. But even a partially transparent menu background still did not visually separate the head from the background scene enough. It looked muddy and cluttered, instead of crisp and bright.

So instead of simply alpha blending, I actually made it desaturate the background (removes the color so it's gray scale), and darken it (like casting a colorless shadow).

I wanted the colorful head to look sharp and bright up against the dark gray background. So the effect looks at the Z buffer to clip out the head in the menu center, so it remains bright and colorful against the dark gray background. That gives it visual "pop" that separates the head from the background. The edges of the effect are feathered, so there's no sharp line dividing the inside and the outside of the menu (useless visual clutter).

The gray shadow just gradually tapers off with distance, suggesting that the pie menu active area extends to the edge of the screen, not confined to the borders of a circle. The labels are drawn with high contrast drop shadows around the pie menu, so they stand out and easy to read, partially overlapping the shadow so they're look like they're part of the menu.

There's special code to perform that particular combination of pixel filters in real time, to every frame just after the 3D rendering phase.

The pixelated censorship effect works the same way as the pie menu shadow, like a Photoshop filter run after the 3D rendering phase. There's a special suit type that's tagged as a "censorship" suit. It consists of bounding boxes attached to the varius bones of the skeleton that you can select to censor. So if you just want to censor the head, you attach the head censor suit to the head bone. The 3D character renderer transforms the 8 vertices but doesn't draw anything, and stashes the screen bounding box away for the pixelation filter to draw later. That's how it can censor just the crotch of naked men, but also the chests of naked girls gone wild.

-Don