Terrain Rendering Glitch with WebGL 2

[ProjectBarks]

Using the latest master branch with cesium there appears to be a significant rendering bug causing terrain to disappear at certain angles and and be occluded with black artifacts at high zoom levels. This seems to be across chrome and firefox. Video of problem

When directly comparing 1.46 and the current master branch this becomes very apparent. This most likely has to do with texture/terrain replacement requests as the more parallel http requests occurring the frequency of artifacts increase.

[OmarShehata]

The video link seems to be broken? (gives me a 404)

[ProjectBarks]

@OmarShehata Updated!

[hpinkos]

Hello @ProjectBarks, thanks for sharing that video. I was able to reproduce this in master using the following example:

var viewer = new Cesium.Viewer('cesiumContainer', {
    contextOptions: { requestWebgl2: true },
    terrainProvider: Cesium.createWorldTerrain()
});

We're working on enabling WebGL 2 by default, and we'll fix this as part of that effort. We have an initial pull request open here: #6314

Thanks!

[lilleyse]

It looks like the problem is log depth related, and the problematic PR is #6701. I thought maybe modernizeShader was doing something wrong with shader translation but it looked fine.

As a workaround, set viewer.scene.logarithmicDepthBuffer = false

[lilleyse]

See #6714 (comment) - it might be the same problem with DISABLE_GL_POSITION_LOG_DEPTH.

[OmarShehata]

I'm closing this since CesiumJS does not officially support WebGL 2, but it is on the roadmap, so we can consolidate known bugs and discussion in this issue: #797 (comment).