This adds a new demo that leverages ImGui. It looks very similar to the
existing material_sandbox demo we have for desktop, with a few
differences:
1. Does not use FilamentApp.
2. Does not draw a shadow plane.
3. Does not use a TrueType font in ImGui. (improves load time)
4. Does not allow the user to spin the model. (will fix soon)
We now have a triumvirate of web demos with a progression in complexity:
1. triangle
2. suzanne
3. sandbox
This is a sufficient set of WebGL samples for now, at least until we
finish creating a proper JavaScript API.
This CL factors out some of the common code with the native sandbox
demo, but keeps the UI definition separate since the web demo has some
minor differences (e.g., there is no shadow plane yet).
Note that using viewport units for height was wrong; it caused a bad
aspect ratio on Android while the URL bar was visible. This is explained
in an article:
https://developers.google.com/web/updates/2016/12/url-bar-resizing
* Introduce two WebGL samples: triangle and suzanne.
This commit has no effect on mobile / desktop builds, it only adds new
targets to the `-p webgl` build.
We will eventually expose a proper JavaScript API, but for now these
samples use a (somewhat under-engineered) `filaweb` framework whereby
the WebAssembly module exposes a small number of C entry points: launch,
render, and resize.
Each sample has two source files: a cpp file and an html file. The cpp
file generates js / wasm pair. The generated js is simply a loader for
the wasm.
The CMake script creates a pristine "public" folder which contains the
minimal set of files needed to serve the web application using a simple
static file server. The public folder like this:
/suzanne.js built by em++ from suzanne.cpp
/suzanne.wasm built by em++ from suzanne.cpp
/suzanne.html copied from REPO/samples/web
/filaweb.js copied from REPO/samples/web
/favicon.png copied from REPO/samples/web
/monkey/*.png copied from REPO/assets/models
/monkey/*.filamesh built by filamesh
/desert/* built by cmgen
To decode PNG textures, we use the somewhat unusual approach of using
JavaScript to draw them into a hidden 2D canvas, then reading back the
pixels. This allows us to avoid fattening up the wasm file with a PNG
decoder. An alternative idea would be to pass a DOM Image directly into
glTexImage2D, but this would require some #ifdefing and/or JS injection
in Filament's OpenGL backend.
* Optimize the suzanne material.
