[FIX] marker occlusion

[Kurtil]

There is two parts here:

• If I am correct, marker.worldPos = marker.origin + marker.rtcPos. Because the occlusion layers uses the marker.originin the shader, themarker.rtcPosshould be used to build positions instead ofmarker.worldPos`.

• The commit XEOK-33 seems to introduce a bug in the occlusion tester because "OcclusionLayer markers' transformation is being applied through the OcclusionLayer::positions array" is not correct... ??

[Kurtil]

annotations_createWithMouse.html.zip

I've updated the annotations_createWithMouse to quickly test this PR.

Comment/uncomment the lines 70 and/or 93 to verify that it is working correctly :)

[paireks]

@MichalDybizbanskiCreoox could you please have a look there? :)

[MichalDybizbanskiCreoox]

Thank you @Kurtil for the PR.

The 1c06e71 commit rectifies an incorrect assignment in the OcclusionTester at 1c06e71#diff-b81e22131b6074c4e31ef6fd6e3cd96cb491eb46ea40497e3beb60b482e400d4
This fix was necessary for a scenario, in which an Annotation (which derives from a Marker) is created, but doesn't appear in the view if its worldPos is set immediately, like this:
annotations.createAnnotation({ occludable: true }).worldPos = [2,0,-1]

The example you provide would work before the fix because of the incorrectness being compensated by the original const worldPos = marker.worldPos; assignment in the OcclusionLayer.js at

xeokit-sdk/src/viewer/scene/webgl/occlusion/OcclusionLayer.js

Line 102 in 08fe285

const worldPos = marker.worldPos;

Your change of this original assignment to use marker.rtcPos seem to not reintroduce the older error (which is great), and at the same time add precision to the occlusion test being performed with the rtcPos property, covering your test case.