Fix disappearing terrain and sky

[bagnell]

• Fixed the sky atmosphere fragment shader that was causing the atmosphere to disappear when near or under the surface of the ellipsoid.
• Fixed occlusion culling to only test occlusion when the camera is not under the surface of the ellipsoid.

Fixes both #2271 and #2415.

[bagnell]

The easiest way to test the sky atmosphere is to set:

scene.screenSpaceCameraController.enableCollisionDetection = false;

and rotate around one of the 3D models positioned on the ground.

[pjcozzi]

I get this atmosphere on Mac in Chrome and Firefox:

Here it is without the globe:

[pjcozzi]

Looks OK near the ground:

[pjcozzi]

When we fix this, can we also add a comment to SkyAtmosphereFS.glsl about the workaround/fix?

[pjcozzi]

Can we also change the default for screenSpaceCameraController.minimumZoomDistance in this PR? What do you think? 1m? 0.1m?

[pjcozzi]

Looks good.

The only other issue is zoom to the dead sea and quickly use the middle mouse button to take a horizon view - the camera will start moving backwards. If this is not an easy fix, submit a new issue.

[bagnell]

@pjcozzi This is ready for another look.

The camera problem you mentioned is intentional. The camera slides over terrain when a collision is detected to prevent it from getting stuck.

[pjcozzi]

Do you get these test failures:

Scene/ScreenSpaceCameraController camera does go below the terrain in 3D when collision detection is disabled
Expected 1.000000000846144 to be less than 1.
Error: Expected 1.000000000846144 to be less than 1.
    at stack (http://localhost:8080/ThirdParty/jasmine-2.2.0/jasmine.js:1475:17)
    at buildExpectationResult (http://localhost:8080/ThirdParty/jasmine-2.2.0/jasmine.js:1445:14)
    at Spec.Env.expectationResultFactory (http://localhost:8080/ThirdParty/jasmine-2.2.0/jasmine.js:584:18)
    at Spec.addExpectationResult (http://localhost:8080/ThirdParty/jasmine-2.2.0/jasmine.js:332:34)
    at Expectation.addExpectationResult (http://localhost:8080/ThirdParty/jasmine-2.2.0/jasmine.js:528:21)
    at Expectation.toBeLessThan (http://localhost:8080/ThirdParty/jasmine-2.2.0/jasmine.js:1399:12)
    at http://localhost:8080/Specs/Scene/ScreenSpaceCameraControllerSpec.js:1059:52
    at Object.<anonymous> (http://localhost:8080/Specs/spec-main.js:137:30)
    at attemptAsync (http://localhost:8080/ThirdParty/jasmine-2.2.0/jasmine.js:1793:24)
    at QueueRunner.run (http://localhost:8080/ThirdParty/jasmine-2.2.0/jasmine.js:1746:26)
Scene/ScreenSpaceCameraController camera does go below the terrain in CV when collision detection is disabled
Expected 1.000000000846144 to be less than 1.
Error: Expected 1.000000000846144 to be less than 1.
    at stack (http://localhost:8080/ThirdParty/jasmine-2.2.0/jasmine.js:1475:17)
    at buildExpectationResult (http://localhost:8080/ThirdParty/jasmine-2.2.0/jasmine.js:1445:14)
    at Spec.Env.expectationResultFactory (http://localhost:8080/ThirdParty/jasmine-2.2.0/jasmine.js:584:18)
    at Spec.addExpectationResult (http://localhost:8080/ThirdParty/jasmine-2.2.0/jasmine.js:332:34)
    at Expectation.addExpectationResult (http://localhost:8080/ThirdParty/jasmine-2.2.0/jasmine.js:528:21)
    at Expectation.toBeLessThan (http://localhost:8080/ThirdParty/jasmine-2.2.0/jasmine.js:1399:12)
    at http://localhost:8080/Specs/Scene/ScreenSpaceCameraControllerSpec.js:1075:35
    at Object.<anonymous> (http://localhost:8080/Specs/spec-main.js:137:30)
    at attemptAsync (http://localhost:8080/ThirdParty/jasmine-2.2.0/jasmine.js:1793:24)
    at QueueRunner.run (http://localhost:8080/ThirdParty/jasmine-2.2.0/jasmine.js:1746:26)
Scene/ScreenSpaceCameraController camera does not go below the terrain in CV with the transform set
Expected 0.9999999948034711 to be greater than or equal to 1.
Error: Expected 0.9999999948034711 to be greater than or equal to 1.
    at stack (http://localhost:8080/ThirdParty/jasmine-2.2.0/jasmine.js:1475:17)
    at buildExpectationResult (http://localhost:8080/ThirdParty/jasmine-2.2.0/jasmine.js:1445:14)
    at Spec.Env.expectationResultFactory (http://localhost:8080/ThirdParty/jasmine-2.2.0/jasmine.js:584:18)
    at Spec.addExpectationResult (http://localhost:8080/ThirdParty/jasmine-2.2.0/jasmine.js:332:34)
    at Expectation.addExpectationResult (http://localhost:8080/ThirdParty/jasmine-2.2.0/jasmine.js:528:21)
    at Expectation.toBeGreaterThanOrEqualTo (http://localhost:8080/ThirdParty/jasmine-2.2.0/jasmine.js:1399:12)
    at http://localhost:8080/Specs/Scene/ScreenSpaceCameraControllerSpec.js:1101:37
    at Object.<anonymous> (http://localhost:8080/Specs/spec-main.js:137:30)
    at attemptAsync (http://localhost:8080/ThirdParty/jasmine-2.2.0/jasmine.js:1793:24)
    at QueueRunner.run (http://localhost:8080/ThirdParty/jasmine-2.2.0/jasmine.js:1746:26)

[pjcozzi]

Mention this in CHANGES.md.

[bagnell]

@pjcozzi The tests are fixed. This is ready.

[pjcozzi]

Awesome.