How to use glPolygonOffset inside fragmentShader to reduce z-fighting

CesiumJS
1

Is it possible to use glPolygonOffset inside the fragmentShader of a PostProcessStage to reduce z-fighting of 3DTiles? I am getting the following error message:
“RuntimeError: Fragment shader failed to compile. Compile log: ERROR: 0:103: ‘glPolygonOffset’ : no matching overloaded function found”.
Thanks in advance!

2

Can you share a bit more context about your issue (a video, picture, or a Sandcastle perhaps). How are you generating your 3D Tiles?

3

Thank you for your fast reply. I have added the new Cesium OSM Building 3D Tiles and a ShadowMap to my scene. I am passing a custom GLSL fragmentshader to my PostProcessStage. I have set the depth bias to 0.0005 and the size of the ShadowMap to 8192 pixels. The following presentation suggested using a glPolygonOffset (page 18ff.): https://cesium.com/presentations/files/ShadowsAndCesiumImplementation.pdf.

image
image1660×737 508 KB

4

I’m actually not able to activate shadows with Cesium OSM Buildings. I get the following error:

DeveloperError: normalized result is not a number
Error
    at new DeveloperError (https://sandcastle.cesium.com/CesiumUnminified/Cesium.js:83:13)
    at Function.Cartesian3.normalize (https://sandcastle.cesium.com/CesiumUnminified/Cesium.js:2040:13)
    at Ellipsoid.geodeticSurfaceNormal (https://sandcastle.cesium.com/CesiumUnminified/Cesium.js:3601:23)
    at Ellipsoid.cartesianToCartographic (https://sandcastle.cesium.com/CesiumUnminified/Cesium.js:3694:18)
    at fitShadowMapToScene (https://sandcastle.cesium.com/CesiumUnminified/Cesium.js:266739:40)
    at ShadowMap.update (https://sandcastle.cesium.com/CesiumUnminified/Cesium.js:266971:9)
    at updateShadowMaps (https://sandcastle.cesium.com/CesiumUnminified/Cesium.js:282471:17)
    at updateAndRenderPrimitives (https://sandcastle.cesium.com/CesiumUnminified/Cesium.js:282494:5)
    at executeCommandsInViewport (https://sandcastle.cesium.com/CesiumUnminified/Cesium.js:282266:7)
    at Scene.updateAndExecuteCommands (https://sandcastle.cesium.com/CesiumUnminified/Cesium.js:282009:7)

Sandcastle I’m testing with. Do you not get this error when activating shadows? If so, can you share a Sandcastle of how you’re initializing your scene?

5

I do not add shadows to OSM Buildings or similar. I am adding a Cesium ShadowMap with a custom LightCamera to my Scene. I would really like to share a Sandcastle of my problem with you but it is really complex and not easy to rebuild. I can try to simplify my problem: How can I reduce z-fighting in my scene? Is it possible to call the OpenGL method glPolygonOffset inside the custom fragmentShader of the PostProcessStage as suggested by Sean Lilley in the presentation (page 21)?

6

Hey, I have read this post and can confirm that glPolygonOffset is supported (console.log(viewer.scene.shadowMap._polygonOffsetSupported) --> true). I think changing the light type from “pointlight” to “spotlight” might be a solution for my problem. But when I set the “isPointLight” parameter to false, no shadows are generated at all.
This is how i initialize my ShadowMap:
this.shadowMap = new Cesium.ShadowMap({ // @ts-ignore context: this.viewer.scene.context, lightCamera: this.lightCamera, enabled: true, isPointLight: true, pointLightRadius: this.visibilityRadius, maximumDistance: 200, size: 8092, softShadows: false, normalOffset: false, fromLightSource: false });

I am running on a windows computer with a Chrome browser (version 83). But I am also facing z-fighting when testing with Firefox, Edge or Internet Explorer.