Interesting Ikea Algorithms https://idea-instructions.com/

https://github.com/carp-lang/Carp

I need to parse a sequence of strings, where one of the values may represent a number n that determines how many subsequent values to group together. For example

;input
["john" "doe" 2 "USD" 200 "CAD" 130]
=>
;output
{:fname "john"
 :lname "doe" 
 :money {"USD" 200 
         "CAD" 130}}

basically i sort of need binding in the middle of parsing a sequence of inputs

Anyone here familiar with debugging WebGL?

I have the classical problem of: I'm running my app, there are no runtime errors in the console, and my screen shows the color of glClearColor, but not the triangle I am trying to draw.

The custom shader also compiled fine. The binding vertec/element-array buffers also works. Somehow, the drawElement is not showing anything.

Debugging OpenGL at the shader level is a bit of a nightmare honestly

I believe I have the projection-matrix + model-view-matrix setup correctly too.

It's not the shader which is at the fault -- the shader literally just outputs a single color.

disable stuff until it works = my OpenGL debugging method

disable the shaders, disable the transforms

disable the projections, lol

The best solution I've found in these scenarios is to pare it back exactly

afaik, WebGL only does shaders, there's no 'fixed pipeline'

Start super simple with one vertex array and a basic shader

I'm literally trying to draw two triangles with a shader that just outputs the attrib values.

Is there no debugging tool that shows my camera + locatin of objects ?

Right so in that case, switch to a single triangle with no view transformation and the screen transform matching the screen co-ordinates

I suspect the camera is pointed at one place, and the objects are drawn elsewhere.

No, since those really don't exist

The thing is those sorts of abstractions have to be built with shaders etc and you'd then work in a higher level engine

The "camera" is purely a construct programmers use to talk about the projection vs object transforms

WebGL is a pretty low level API

Another option is to switch to using a scene graph

It might help to see some code?

I would try to draw a single triangle first with a vertex/fragment shader and some hard coded matrices

Or depending on what you want to achieve maybe use a higher level library like Three?

@qqq a helpful exercise is to write a simple rasterizer, you will understand why there is no spoon 😉

although for this particular thing, step 1 is to just use the vertices in your vbo as is (e.g. make a triangle with the coords (-1,-1), (1, 1), (1, -1)) and paint it a different color than your clear color in your shader

step 1 is the problem

I've even sprinkled (. js/cnosole log (.getError gl)) evberywhere, and they are all returning 0

n/m; woot, got triangle to appear!

white triangle on a black screen, the hello world of OpenGL.

Made 50x harder in WebGL.

"Back when I was a kid we didn't have VBOs and shaders, we called glVertex3f in a loop like god intended!"

funnyily enough, it wasn't a webgl issue, it was a clojure issue

I was using ::width ::height on a "window object", but was in the wrong namespace, so I got nil, which (/ nil 2) ==> gave me 0, which screwed up all the projection matrices ...

Huh, never knew that (/ nil 2) was 0 in ClojureScript. It raises an exception in Clojure/JVM

@andy.fingerhut: that threw me off too

Reminds me of this 4-minute talk by Gary Bernhardt, which entertainly pokes fun at weirdness in some dark corners of Ruby and JavaScript: https://www.destroyallsoftware.com/talks/wat