Develop Reference

Rendering huge, interactive SVGs in a browser

We have to display huge SVG documents (about 20mb) inside a web application. Users should be able to zoom in and move the image.
Rendering the SVG directly as a DOM object is too slow and the performance is inconsistent. The same applies for painting it on a canvas.
Generally, handling SVG on the client side seems weak. So I thought of implementing a server-side solution for providing the data in small chunks, in a non-vector format. If the user is not interacting with the document, the buffer starts lazy loading higher detailed pieces. My concern with this solution is, that the network traffic could be critical.
We will be rendering 2D DWG / DXF files, which will be converted to SVG.
The AutoCAD API seems really slow. The DWG sample does not work on any of our devices. Also, the application has to run without an internet connection, so we can't use the AutoCAD REST API.
How would you solve this? Are browsers even built for handling huge vector graphics?

When it comes to SVG it depends on the number of nodes, gradients, opacity and blur effects; however, why not use the end-user's graphics accelerator to handle this?
Most modern web browsers are made to support graphics acceleration through WebGL -with which you can build very complex (and "huge") rich graphics in 2D (or 3D) that is handled as fast as your graphics accelerator can handle it; exactly like modern games.
Using a WebGL library is recommended where a lot of work has been done for you already:
PlayCanvas : https://playcanvas.com/ -- you can import other formats, build & script your scenes with a friendly interface. PlayCanvas is well documented.
Three.js : http://threejs.org/ -- an advanced WebGL library, aimed at coders. ThreeJS can also handle many different types of 3D formats and this library is also well documented.
With Three.js you can also render your graphics as SVG, however, using WebGL is recommended for the obvious advantages in speed and quality.
Both of these libraries are very powerful, have an active community and is well supported in modern web browsers; however there are many others you can try.
For more information on the libraries mentioned above, it's best to visit the sites where extensive information and examples are available.

Instead implementing yourself, I would suggest you use the Autodesk Viewer, also available for developers with full REST + JavaScript APIs.
Basically this library will convert your DWG file (2D or 3D) into a JSON stream and adjust the amount of data according to the browser/device capabilities. It uses Three.js, but you don't need to handle the geometry directly (but you can).
Check the Forge Github for samples. I like the Galley better.
You may also run it locally using NodeJS to server it to the browser. The Extract sample does the whole process.

WebGL graphics rendering engine

So, I have thought about designing a WebGL Graphics Engine, which will facilitate designing 3D Interactive Graphics for web. Now, my question is :
WebGL is Javascript API, so in order to design an engine for WebGL graphics, do I need to have a JavaScript compiler or anything ? What I want is a system which will let users see what they are creating (for example, like blender workspace, if you draw up a scene you can see and make changes simultaneously)

You would have to create some kind of engine, or framework that you'll build your system onto.
Creating only framework/engine would take at least 2-3 months, and if you plan creating something really big and advanced, that supports various effects rather than simple rendering primitives, than that might come down to 5-6 months. After that you could start creating your web application. So 6-7 months time for that? That shouldn't be a problem.
I don't know how advanced you are, how many people are you working with, but that seems very plausible and doable. But is worth of it? In a year, many different things will change, maybe new openGL ES version for webGL, changing api, supported browsers (IE recently joined the game),... it's really questionable.
You wouldn't need any kind of JS compiler or anything like it, just knowledge of advanced JS and many different techniques used in 3d, and since you plan building system that is far beyond just-graphic-stuff, then it adds even more to overall complexity and time consumption.
So, to answer your question: yes, it's very doable in a year, but will it pay off?
Similar things already exist in some form:
http://errolschwartz.com/projects/threescene/
http://badassjs.com/post/12885773103/threenodes-js-a-visual-webgl-scene-editor
CopperLicht engine has its own real-time editor
there are more lab-playground-like editors

Recommended API and IDE to work with WebGL

I'm about to use WebGl in a academic project to preview some 2d and 3d models in a given format.
While I'm reading some documentation, I would like to know, from your experience, what would be the best API to speedup development and abstract some low-level calls and also the best IDE to work with it.
Cross browser compatibility is not a major problem.
I've decided about WebGl because I would like to create a web interface for my project to help sharing my progress.
Do you even recommend using WebGl for that?

At the end of the day, an IDE is only meant to help a little, you do the hard hauling, having said that, the best editor(s) I use for javascript are Sublime Text and Netbeans IDE
Then as it was already stated, Chrome DevTools is your best bet for debugging.

API
Three.js is really awesome to work with regarding developing WebGL apps. It makes creating what you want very easy (create a scene object, create some things you want to show, then add them to the scene and render. No need to mess around with GLSL and low level stuff right off the bat, although you could if you really wanted to).
IDE
Chrome's console and various tools are great for debugging in general. You can use whatever text editor / IDE for javascript that you want.

API (Framework)
If three.js is hard for you, or you are professional developer who just don't want to spend his time on simple things like setting up environment(scene, camera, renderer) you may try whitestorm.js.
WhitestormJS framework is a wrapper around three.js (you can use both at once, like jQuery wraps DOM). It has some extra features:
Built-in physics of Bullet Physics 3, even softbody physics (You can use light version without physics.
It has component structure (like ReactJS). You can share your plugins, components and use the ones from others.
*WhitestormJS is non-commercial open-source project by three.js fans.

HTML5 Canvas / Flash substitutes?

I'm looking for a good plugin for:
a) rapid rendering of
b) lines, shapes, and imagery on top of a
c) rectangular canvas area who's size can be declared at load time.
It needs to run at 20-30fps without putting a heavy load in the browser. It also needs to be able to interface with JavaScript and the DOM.
Creating my own Flash plugin is the first choice, but I'd like to aim for a free, open-source and/or non-proprietary solution first. HTML5 canvas is out of the question - it renders way too slowly.
Anyone happen to know of anything that does these features? (I'd even be okay with a pre-made Flash plugin that meets the requirements mentioned above)

Your request is still vague. What do the lines and shapes need to do? Sit there looking pretty?
If your lines, shapes, and imagery are going to be fewer than say 5,000 objects total, I'd recommend using SVG and perhaps the Raphael library to go with it. Every SVG object is a DOM object from the get-go, which will save you some associated headaches with trying to use Flash or Canvas.
If you really need a lot more performance or plan on having 50,000 objects on screen, Canvas may be for you.

"Creating my own Flash plugin is the
first choice"
I'm unclear what you mean by "plugin" here - I assume you just mean "flash file" (an SWF?).
I think #WTP is making a good point. You say "rapid rendering" but of what? how complex is it? Flash has very good speeds when it comes to vector graphics, and much faster rendering of optimized bitmap data (the technique of choice is blitting here). It all comes down to optimizations / complexity of graphics. No matter the plugin / tech solution, you will always be able to cripple a machine with inefficient design.
To answer your question, Flash will definitely meet your needs.
I would also venture that Canvas/JS would as well, but apparently you've tried that already? I've seen quite complex scenes running quite rapidly, so that surprises me.
I'll note, also, the upcoming Molehill APIs for Flash. This provides low-level access to the GPU - and will create the potential for breathtaking 2d/3d performance in the browser. But its still in alpha, so... don't hold your breath ;)

I know of only four major players in the "Vector graphics capable" department -- HTML Canvas, Flash, Silverlight, and Java applets. Aside from canvas, all them are proprietary in some way or another. The good news is that all of them have the ability to compile for free in some way or another and they are generally faster than canvas by my understanding. Now, I happen to know Flash so that might color my opinion, but I am fairly certain that it is your best option. It has decent performance and a solid install base. It also runs on Linux and does not raise major security issues.
Look up the Flash Builder (Flex) sdk. There is command line compilation for it.

JavaScript vs AS3 for Interactive Globe

I am developing a web application that should display data points below the Earth's surface. It should also include user navigation, zoom, and rotational capabilities. It reads in the data from a XML file and should display 500-1000 spheres. Ideally, I would like to use HTML5, but it doesn't run in IE8.
This is a Flash application that is somewhat similar to what I want (minus the globe around the spheres):
http://demo.tufat.com/applets/molecule/index.html
There is also a good jQuery application that allows for 3d rotation out there.
So, the question is JavaScript/jQuery or AS3? I know Flash handles large amounts of data better but is Flash dying out? The application must run efficiently on most browsers.

Flash is not dying. I am not sure which Blogging Social Media Expert told you that.
Choose a language and just stick with it. Unless you know how to handle your memory and work with Paper Vision or Unity you should go with JavaScript for most likely you will end up with leaks if you do not do garbage collection, 500-1000 spheres is alot.