Fast GPU color transforms with XNA

Filed under: XNA

Some time ago I came across a nice Siggraph paper on Using Lookup Tables to Accelerate Color Transformations and since then have been interested in seeing it at work.

The basic premise is that a 3d texture is used as a lookup table where the input 3d coords represent the input colour. A nice and simple fragment shader is then used to access this lookup texture and return the transformed color. Any number of any complexity operations can be stored in the lookup texture as long as you’re mapping the single input pixel (that is, no neighbours). Gamma correction, contrast, saturation, colorisation, levels, colour keying etc, are all possible in any combination at a fixed small cost.
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Tags: effects, shaders, XNA

Lumines type ’scanner’ with fireflies

Filed under: Game Maker

Something neat I ran into today; a little proof of concept for a Lumines kind of effect. Only, prettier.

Fireflies

Tags: effects, tutorials

Realtime Dynamic Light

Filed under: Game Maker

This is a little bit of history, the very first lighting system for game maker. Prior it was thought impossible to achieve. It works quite different from its modern cousins because surfaces didn’t exist back in the day. It’s obviously not for actual use, I thought thought it would be nice a post a page in GM history. Although several people have emailed me about it, one even intending to use it. I’m not sure why, but here you go.

While the thing itself is outdated, it still shows some good things to learn from like drawing smooth outlines around sprites and some uses for luminance scan, which you’ll find in every modern lighting engine.

Realtime Dynamic Light

Tags: effects, tutorials

Smooth loading bar

Filed under: Game Maker

You might have seen this as part of an older GUI demo I posted. It’s a really smooth circular progressbar type thing. I just ran into it and thought it’d be nice to share. I still have to figure out what to do with my smaller creations.
Incidentally, I went and found the demo in question and linked it here, even though I’ve lost the source to that particular build and can only offer an exe. I still think its a good little demo to look at as it demonstrates a number of things I takled about working in concert: interface, eyecandy, my object importer (here it is used to fetch content from the web and run it). You’ll find the demo at 64digits.

As for the sample itself… Progress ring.
And don’t fret, the editable for my GUI in it’s latest form is coming.

Tags: effects, interface, tutorials

Fake environment mapping

Filed under: Game Maker

A little trick I did to show that some limitations of d3d can be cheated around. Here we have a reflective surface. This is achieved by resolving a model’s vertices into screenspace (once again game maker limits and provides no transform functions so I had to pretty much duplicate d3d output with scripts). It is however, very limited and only shows the idea. To make it work in a game with a camera, you’ll need to do a bit more in the way of transforms.

Oh yeah. The i3d format it uses is produced by my mesh exporter also available here.

Reflections

Tags: 3d, effects, snippets

2D Metaballs

Filed under: Game Maker

The challange was to draw a 2d fluid. The solution was very interesting. Because actually solving marching cubes or similar was too slow in Game Maker, I designed an ‘analog’ approach. This works on a surface. First we draw whatever the fluid ‘world’ may be - that is, what the fluid area will actually show. Like a liquidy red version of the screen for blood, or a gradienty blue version for water, etc. Then we do a bit of magic and overwrite the alpha of that surface with the alpha of particles representing the fluid area. Last but not least, we achieve thresholding without alpha testing which is unsvailable in game maker by multiplying the alpha values by themselves several times much like the contrast ramp phase of a bloom filter.

The technique of overwriting a surface’s alpha chanel alone is useful in many other applications, but I’ll let you think about that.
Oh yeah one more thing. The demo itself looks different from both these screenshots. And probably less pretty. Fiddle with it yourself to achieve the style you want. You’ll be wanting to play with the step script, which is sufficiently commented to navigate.

Metaballs!

Tags: effects, eyecandy, tutorials

Advanced Seeking Missiles

Filed under: Game Maker

Another bit of deliciousness from my GM folder. I made it after watching Battlestar Galactica. I learned a lot about homing missiles, like the fact that the tracking system isn’t as important as target selection. Anyway, it’s all there. With not much help or comments as usual :P.

Clicking the mouse will launch a few missiles in concert. Their super cool advanced AI will have each pick a target which can be hit in the least amount of time, and avoid designating more than one missile per target unless there are more missiles launched than targets to pick from. After that a tracking algo kicks in which simulates a limited amount of fuel which is used up by turning. The tracking algo is deadly efficient and predicts where the target is going to be. If the missile runs out of fuel before hitting, it’ll just keep flying in a straight line. If its target is destroyed by another missile, it’ll intelligently try to pick another target which its most likley to be able to hit. Not only is this a good demo to learn from, it’s also good for actually putting ideas to a test. With a bit of work you can make a much larger room and spawn a lot more enemies and have it launch missiles automatically. What you’ll end up with is an equilibirum of targets being spawned and shot down. As you tweak the AI the number of targets onscreen at any time will go down if you made a good change or up if it was a bad one.

Oh and if you haven’t realized, the ribbon trails here are the same ones as you’ll find in my ribbon trail sample. Only, that one is nice and commented and stuff.

Fire Ze Missiles!
Compiled EXE by popular demand.

Tags: ai, development, effects

Shockwave

Filed under: Game Maker

This is a little distorting shockwave effect. You might remember it from my very impressive Kill Catalyst screenshots on 64digits. It’s not quite so impressive in the demo, but if tweaked a bit and used right, will be awesome.

Shockwaves

Tags: effects, eyecandy, tutorials

Distorting Energy Beams

Filed under: Game Maker

This is really neat. It’s a few things in one. First and foremost it handles linear screenspace distortions. We’ve done shockwave rings, but lines turned out to be a bit more tricky. This shows two methods of doing it. One very pretty but slow one by creating several point distortions, and one fast but less pretty one with a few quads. It also shows how to do lightning that follows a linear path, and how to go about making awesome energy beams in general.

As with must stuff coming out of my GM folder, there’s no help file or explanations. If you want to use this, you’re going to have to pull it out yourself.

Linear distortion

Tags: effects, eyecandy, tutorials

Textured ribbon trails

Filed under: Game Maker

Ribbon trails are very pretty if used right. In fact even if used wrong they’re still pretty most of the time. I don’t know why no one has done this before. I saw scripts that drew them with circles which gets slow or ugly if you go fast, and with lines, which is limited to 1px in width. The obvious thing to do of course is to use a primitive.
So we make a list containing coords of where we’ve been for the past N steps, and then draw it. I’m not going to explain the intricacies of the drawing script but everything is very straightforward and you shouldn’t have problems figuring out how to use it.

When doing mouse decorations or trails, never have them snap to the mouse position! The mouse is a precise input device which is good most of the time but in the land of eyecandy it means jerky, ugly movements. Instead have the decoration follow slowly as I do here. It makes a world of difference.

Ribbon trails

Tags: effects, eyecandy, tutorials