let rotX =0, rotY =0,
perspective =500,
depth,
currX, currY;// learned something like this at Andries Odendaal's www.wireframe.co.za function point3d(x, y, z){
let cosX = Math.cos(rotX),
cosY = Math.cos(rotY),
sinX = Math.sin(rotX),
sinY = Math.sin(rotY),
posX, posY, posZ;
posZ = z * cosX - x * sinX,
posX = z * sinX + x * cosX,
posY = y * cosY - posZ * sinY,
posZ = y * sinY + posZ * cosY;
depth =1/ (posZ / perspective +1);
currX = posX * depth;
currY = posY * depth;return[ currX, currY, depth ];}
Here’s is an example of it in action:
I’ve used this code many many times, it’s just easy to throw into any language and instantly get 3d points rendered in 2d. Here is a short video of a Java applet from 2003 called “Catch Env” that made use of it:
You’ll notice in that source, that I nested the equation to allow for local and global transformations. It was around that time that I learned the ins and outs of real 2D and 3D matrix transformation math… Ken Perlin’s classfiles from NYU were a real help when I was learning that stuff. I don’t think this was the exact file I was working with, but it was definitely on his site somewhere.
Before all that, during my junior year in college I created a 3d engine based off Odendaal’s code in Director (Lingo). Here is a video of some of the demos for it:
…and here is a strange screenshot from my personal website at the time:
Just an example of a powerful snippet and a gateway to learning matrix transformation math. When I first really dug in to html5 canvas - before WebGL was supported so widely - having this trick up my sleeve was great. As you can see in the below link, I used it more than a few times back then:
Around 2015 I had the idea for a PRNG that would clamp itself and have moments of “smoothness”. When I got around to trying to create such a thing, the result was something I jokingly called the “Hermit Crab Curve”. I also called it the “Shard Curve”.
The equation for the curve defines a radius in polar coordinates:
Where a and d are paramters that control the detail of the curve. o is a rotation and offset value for the angle and s is a scalar. Note the use of rem. The resulting curve is much less interesting if a standard modulo is used in place of a remainder:
The above variable values were found using this interactive version of the equation:
To illustrate how you might use this as a PRNG I created this fork of the above pen:
This snippet shows a simple method to do frame differencing with a web cam. This is useful for detecting which areas of the screen have change from frame to frame. This post assumes you pretty much know what frame differencing is.
This is one of those things I do a good deal but never wrapped up into a library... it's easy (for me at least) to forget exactly how to set it up from scratch.
I added an extra buffer because it's pretty common that you'll want to other things aside from just frame differencing alone, so it's nice to have it all wrapped up in a buffer BitmapData that you can use elsewhere. If speed is a real concern, you can do away with the buffer and just use the canvas instead - depending on what kind of analysis your doing on the frame differenced image it may be trickier without the buffer.
