Overview
Introduction
This tool animates a handful of randomly colored, randomly moving shapes on a canvas, then records that live animation into a real, downloadable video file.
It's a hands-on demonstration of turning canvas drawing into video: the same technique used by in-browser screen recorders and canvas-based video export features.
What Is Random Video Generator?
A generator that picks a random scene, a set of circles, rectangles, and triangles with independent positions, velocities, sizes, and colors, then animates and records it.
The animation itself is simple: each shape moves in a straight line at its assigned velocity and bounces off the canvas edges, for as long as the chosen duration.
How Random Video Generator Works
A pure function first picks the random scene: for each shape, a type, starting position, velocity, size, and color, entirely independent of the canvas rendering itself.
The client component then runs a requestAnimationFrame loop that redraws every shape's new position each frame based on elapsed time, bouncing velocity off the canvas edges.
While that loop runs, canvas.captureStream() exposes the canvas as a live MediaStream, and a MediaRecorder captures that stream into WebM video chunks, which are combined into a downloadable Blob once recording stops.
When To Use Random Video Generator
Use it to see a working example of canvas-to-video capture, or to quickly generate a short, random animated clip for a demo or placeholder asset.
It's a good fit for prototyping or testing any feature built around recording canvas animations, rather than for producing polished final video content.
Often used alongside Random Audio Generator and Random Image Generator.
Features
Advantages
- Demonstrates a complete canvas-to-video pipeline entirely client-side, no server-side video encoding involved.
- Shape count, duration, and canvas size are all adjustable.
- Every regeneration produces a genuinely different set of shapes and motion.
Limitations
- Browser support for canvas.captureStream() and MediaRecorder's WebM output varies significantly; this feature is primarily reliable in Chromium-based browsers (Chrome, Edge) and may not work at all in some other browsers.
- Motion is simple straight-line movement with edge bouncing, there's no physics, collision between shapes, or easing.
- Duration is capped at 8 seconds to keep recording and file size manageable in the browser.
Examples
Best Practices & Notes
Best Practices
- Test in a Chromium-based browser first if the recording doesn't seem to start, since MediaRecorder support is the main compatibility risk here.
- Keep shape count and duration modest for faster recording and smaller file sizes.
Developer Notes
The shape parameters (position, velocity, size, color, type) are generated by a pure, DOM-free function so that part is directly unit-testable; the canvas animation loop and MediaRecorder capture necessarily live in the client component since neither requestAnimationFrame-driven canvas painting nor MediaRecorder exist outside a real browser.
Random Video Generator Use Cases
- Demonstrating canvas.captureStream() + MediaRecorder video capture
- Generating a quick random animated placeholder video clip
- Testing a video upload or playback feature with freshly generated WebM content
Common Mistakes
- Assuming this will work identically in every browser — MediaRecorder codec/container support genuinely differs, check content.limitations before relying on it.
- Expecting smooth physics or collisions between shapes; motion here is simple constant-velocity movement with edge bouncing only.
Tips
- If recording fails silently, check your browser's MediaRecorder support for WebM before assuming the tool is broken.
- Lower the shape count if the animation looks too cluttered at your chosen canvas size.