Introducing Phystrivo: pixel physics for game effects
Hand-animating a sprite burning, exploding or crumbling takes a lot of time. Every flame, chunk and drip is drawn frame by frame, and if it’s not quite right, you start again.
So I started building Phystrivo: an app where you bring in your pixel art, click on it, and watch real pixel physics do the work. When it looks right, you export it as an animation for your game.
How it works
You load a sprite, choose an effect and click. Every pixel is simulated, so no two runs look the same. When you get one you like, you can export it exactly as you saw it. Phystrivo records what you did, so the export plays back the same run at whatever frame count and scale you choose.
The effects
- Fire: spreads through the pixels and leaves smoke, embers and charcoal behind.
- Impact: aim a shot and it hits the first pixel in its way.
- Explode: pixels break off in chunks, fly, and land in a heap.
- Melt: the sprite glows, softens, and runs down into a puddle.
- Dissolve: the sprite drifts away pixel by pixel.
- Slice: drag a line and the pieces slide apart and fall.
- Shock: a jolt crackles through the sprite and can leave scorch marks.
- Freeze: frost spreads until it’s solid ice. Then click again to shatter it.
- Cloth: flags, capes and banners that hang from their pins and move in the wind.
What things are made of matters
Each layer has a material: wood, metal, stone, cloth, flesh or bone. Wood burns, metal doesn’t, and a shock runs furthest through metal and flesh. Layers stack front to back, so you can have clothes over a body over a skeleton, and each one reacts in its own way.
You can import a PNG, or a whole Rastrivo Studio project with each of its layers coming in separately.
Ragdolls (and optional gore)
Turn on Ragdoll and a skeleton sits inside your character. A shot or a blast knocks it over, and it tumbles to the floor. For games that want it, there’s optional gore and dismemberment, and a backdrop layer that catches the splatter.
Weather
Rain and snow can fill a whole game screen. Snow settles and builds up on whatever it lands on. Weather can loop seamlessly and tile, so one short export covers any screen size.
Exporting
You can export a GIF (with real transparency), a sprite sheet, PNG frames, or a Rastrivo animation to keep editing in Rastrivo Studio. You can also export just the effect on its own as an overlay, and play it forwards, backwards or ping-pong.
What’s next
Phystrivo is coming soon to Windows on the Microsoft Store. I’m working on the final polish now: undo, keyboard shortcuts, and remembering your settings between sessions.
After launch, I’d like to add things you can pour, such as petrol, oil and water, that react with fire and each other.
I’ll be posting clips along the way on Bluesky and YouTube, so follow along there. If you make games and there’s an effect you’d love to see, email me at support@denbisoft.co.uk.