Cesium: Imagery stops loading when changing terrain in request render mode

[hpinkos]

Easiest way to reproduce

• Zoom in close to the ground and hit the Disable terrain button until the imagery stops loading in (usually 2-5 clicks)
• Hit the Enable terrain button
• Now the imagery never loads in, even after the camera moves

I wasn't able to reproduce this when requestRenderMode: false, so it seems to be related to those changes.
It seems like it might be related to changing the terrain before all imagery tiles are loaded, but I'm not sure.

var viewer = new Cesium.Viewer('cesiumContainer', {
    requestRenderMode : true,
    animation: false,
    timeline: false
});

var cesiumTerrainProviderMeshes = new Cesium.CesiumTerrainProvider({
    url : 'https://assets.agi.com/stk-terrain/v1/tilesets/world/tiles',
    requestWaterMask : true,
    requestVertexNormals : true
});
viewer.terrainProvider = cesiumTerrainProviderMeshes;

Sandcastle.addToolbarButton('Enable terrain', function() {
    viewer.terrainProvider = new Cesium.CesiumTerrainProvider({
        url : 'https://assets.agi.com/stk-terrain/v1/tilesets/world/tiles',
        requestWaterMask : true,
        requestVertexNormals : true
    });
    viewer.scene.requestRender();
});

Sandcastle.addToolbarButton('Disable terrain', function() {
    viewer.terrainProvider = new Cesium.EllipsoidTerrainProvider();
    viewer.scene.requestRender();
});

[hpinkos]

@ggetz any ideas here? Let me know if you have trouble reproducing it

[ggetz]

@hpinkos I can reproduce, but I need to take a closer look to see what's causing this.

[hpinkos]

@ggetz while it's not as bad, I'm definitely still seeing problems with this. Please look into it further for next release. Thanks!

[mramato]

@hpinkos can you list steps to still reproduce this. I know we fixed the initial issue, but we should really fix this completely as reliability is really important when using requestRender.

[hpinkos]

@mramato I'll have to trace what's going on in composer to figure out a way to reliably reproduce it. It's really easy to reproduce in that application but difficult to reproduce with the sandcastle example I put together.

[lilleyse]

This likely won't make it into 1.44 but I've leave the next release label.

[mramato]

@hpinkos, @ggetz is this still planned for May 1st? If not, we really need to fix it for June 1st.

[hpinkos]

Sorry, didn't have time to look into it this month

[ggetz]

I think this will need to be bumped to next month, I need the steps to reproduce this.

[ggetz]

@hpinkos Could you take a look at providing steps to reproduce?

[hpinkos]

@ggetz yes, this is next on my list as soon as I wrap up the few features I'm working on

[hpinkos]

Probably not going to have a chance to look at this for the July release, but I'll have a reproducible example ASAP so we can fix this for the August release

[hpinkos]

Well, I actually can't reproduce this anymore. @mramato reopen this if you still see it