Three.js canvas particles don't render with OrthographicCamera

Question

If I take the Three.js canvas_lines demo and replace the perspective camera with an orthographic one:

-    camera = new THREE.PerspectiveCamera( 75, window.innerWidth / window.innerHeight, 1, 10000 );
+    camera = new THREE.OrthographicCamera(-window.innerWidth/2, window.innerWidth/2, -window.innerHeight/2, window.innerHeight/2, -100, 10000);

it causes the particles to no longer render, though the lines show up. Is this a bug in Three.js or in my understanding of orthographic projections?

Image of the particles before the change:

And after the switch to OrthographicCamera: (notice the particles missing and lines terminating in empty space)

Answer 1

The "missing" particles are simply being culled because they do not lay between the camera's near and far zPlanes.

Firstly, the nearPlane on the OrthographicCamera is not properly set. It's sort of tricky, but the z values for the projection matrix have to be >0. This is because they are specified as "distance in front of camera." So, first change:

    camera = new THREE.OrthographicCamera(-window.innerWidth/2, window.innerWidth/2, -window.innerHeight/2, window.innerHeight/2, 1, 10000);

More importantly, the camera should be positioned so its not in the middle of the particle cloud. I just moved it back like this:

camera.position.z = 1000;

In orthographic projections, the z position really only determines culling behavior. The scene still looks the same. Here's the output: