The BitBull Blog

I’d been thinking for a while that I needed a slightly more visceral feel to the collisions in Jetboard Joust, particularly when the main character crashes into the terrain but also when he’s taking damage from enemies.

So I’ve spent the last couple of days working on this by applying three different effects, the amount of each effect applied depends on the strength of impact (ie the speed the player is travelling or amount of damage taken) and is tweened back to zero over a short period of time, roughly 0.25 seconds. The three effects are as follows…

1. Scanner Distortion
It didn’t make sense to me that the scanner display should remain pristine when you’re taking a pummeling. Though the scanner is part of the HUD I imagine it as being embedded in the player’s helmet or something so it should appear to suffer as the player does whilst still maintaining enough legibility to make the game playable. I’ve achieved this by applying a ‘pixelator’ type shader that is based on my ‘teleport’ shader with a few changes. As well as changing the amount of pixelation based on the strength of impact I also add a small amount of brightness and noise which gives the impression of old-school CRT interference.

2. Camera Shake
This effect has become so much a staple of indie games that it’s almost a cliché by now but, what the hell – it looks good! Applying the effect was a bit more complex than I thought as it needs the appearance of randomness without being genuinely random (because a genuinely random shake can appear to stick at times). My final approach was to take a {1,0} vector, rotate pseudo-randomly, and then multiply the camera offset by the strength of impact on the x and y axis. For the pseudo-random rotation I always rotate by at least 90deg from the last ‘shake’ and then add another random amount between 0 and 180deg, this gives the appearance of randomness but always ensures there’s a ‘whole lot of shaking going on’. I also keep track of the ‘static’ camera position so that the ‘shaken’ position is always offset from the ‘static’ position and you don’t get a ‘brownian motion’ type effect with the camera movement which would upset the standard camera taking of the player.

3. Impact Shader
This was the effect that took the longest to get right. In my head I wanted an effect applied to the terrain that was kind of a cross between ‘double vision’ and the ‘vibration lines’ you might see on static illustrations to give the impression of movement. I also wanted the effect to look a bit glitchy.

First step was, whilst the effect was in progress, render the entire terrain to an offscreen image rather than rendering directly to screen. The shader could then be applied to the entire terrain rather than each individual component of it which would be both inefficient and cause visual issues.

I then started by applying a shader that simply rendered the whole terrain in a flat colour with some scaling distortion applied, the scaling varying according to strength of impact. I found I had to apply this shader three times in order to get the ‘double vision’ effect on the top, left and right of each building.

I then tried applying some raster lines to the effect and found this looked best if I applied horizontal raster lines when the shader was distorting vertically and vice versa. This gave a ‘vibration line’ effect around the buildings.

Next I tried randomizing the amount of scaling every x pixels – so there would be more distortion at certain, regular, points. This gave a ‘spiky’ effect to the shader that I thought looked pretty cool.

Lastly I varied the amount of scaling distortion on each axis based on the direction of the player’s travel and also added a certain amount of pixelation, again dependent on the direction of travel. I’m pretty pleased with the effect now though it has taken a hell of a lot of tweaking to get this far. No doubt I won’t be able to resist tweaking it some more either!

Dev Time: 1.5 days
Total Dev Time: approx 44 days

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