Emscripten code and three.js

Question

I would like, if it's possible, to use Emscripten code generated from C/C++ with the Javascript library three.js. For example, from emscripten code I want to pass rendering information to the three.js that will be showed in the browser.

So, can someone give me an idea of how to do that?

Answer 1

You have multiple ways to interact from c++ to javascript. I can show you one way I find quite handy:

in the js library file

// here you write JS "handlers"
mergeInto(LibraryManager.library, {

   new_cube: function(size, color) {
      var cube = new THREE.Mesh(
         new THREE.BoxGeometry(size, size, size),
         new THREE.MeshBasicMaterial({ color: color })
      );
   }

});

in c++

extern "C" {
    extern void new_cube(const int size, const char* color);
}

int main() {
  new_cube(10, "red");
  return 1;
}

in the build command

emcc source.cpp --js-library src/library.js

for easy debugging (but very slow)

#include <emscripten.h>
void emscripten_log(const char* string, bool escape = true)
{
    char buff[1024];
    sprintf(buff, (escape ? "console.log('%s');" : "console.log(%s);"), string);
    emscripten_run_script(buff);
}
void emscripten_debugger()
{
    emscripten_run_script("debugger");
}