I found a weird behavior when setting the camera rotation property.
This is reproducible in the playground, I have prepared a few scenarios:
(is setting camera.Rotation even the correct way to rotate the UniversalCamera?)
Full playground:
https://playground.babylonjs.com/#F68Z6N
preamble
var scene = new BABYLON.Scene(engine);
var camera = new BABYLON.UniversalCamera("camera1", new BABYLON.Vector3(0, 20, 0), scene);
camera.setTarget(BABYLON.Vector3.Zero());
camera.attachControl(canvas, true);
var light = new BABYLON.HemisphericLight("light", new BABYLON.Vector3(0, 1, 0), scene);
light.intensity = 0.7;
var sphere = BABYLON.MeshBuilder.CreateSphere("sphere", {diameter: 2, segments: 32}, scene);
sphere.position.y = 1;
sphere.position.x = 3;
var ground = BABYLON.MeshBuilder.CreateGround("ground", {width: 5, height: 10}, scene);
Scenario A: default
Scenario B:
camera.rotation = new BABYLON.Vector3(Math.PI / 2, 0, 0);
Scenario C:
camera.rotation = new BABYLON.Vector3(Math.PI / 2, 0, Math.PI);
Scenario D:
camera.rotation = new BABYLON.Vector3(Math.PI / 2, 0, 0.001);
Scenario E:
camera.rotation = new BABYLON.Vector3(Math.PI / 2, 0, 0.001);
scene.render()
camera.rotation = new BABYLON.Vector3(Math.PI / 2, 0, 0);
This does not just affect the Z-Axis:
Scenario F
camera.rotation = new BABYLON.Vector3(Math.PI / 2, 1, 0);
Scenario G
camera.rotation = new BABYLON.Vector3(Math.PI / 2, 0, 1);
scene.render()
camera.rotation = new BABYLON.Vector3(Math.PI / 2, 1, 0);
Note: just calling scene.render beforehand is not enough, you actually need to set it to a different value, then render, then change the value again.
Now, I haven’t though too long about what the correct behavior actually should be, but the fact alone that B and E (or F and G) are different should show that something is wrong.
Obviously they are the same. Actually this is quite scary to have different results in different browsers while the code is the same! 
