1. A concise explanation of the problem you're experiencing.
When a polygon has perPositionHeight and is not extruded, attempting to set a heightReference (RELATIVE_TO_GROUND or CLAMP_TO_GROUND) gives the following error:
DeveloperError: Appearance/Geometry mismatch. The appearance requires vertex shader attribute input 'applyOffset', which was not computed as part of the Geometry. Use the appearance's vertexFormat property when constructing the geometry.
2. A minimal code example. If you've found a bug, this helps us reproduce and repair it.
Here is a sandcastle that demonstrates the issue. You can double-click the map to attempt to clamp the polygon to ground:
3. Context. Why do you need to do this? We might know a better way to accomplish your goal.
I was able to change the heightReference on polygons I'd created in 1.46 without a problem, and I would like to keep using the same workflows I've been using.
4. The Cesium version you're using, your operating system and browser.
1.48
Windows 10
Chrome
I was able to avoid the error by setting the value via a Callback Property rather than directly. Using a Callback Property will mark that property of the entity as dynamic.
Unfortunately I don’t think this solves the problem. The entity wasn’t actually being updated in your example, so I added the line “entity.polygon.heightReference = newHr” and the error reappeared.
Sorry, I see - I went and reset it to a constant property. I’m having trouble getting it working in my own code, but I see how the example works now. Thank you.
So it turns out when I start by setting the heightReference result to CLAMP_TO_GROUND, rather than starting with NONE, the error occurs even when using a callback. Here’s the example; the only difference between this and the last example is in line 18.
So I’m only getting the error if perPositionHeight is enabled. I don’t think you need it for this case. Instead, make sure you specify the height, and use a value that will put the entity above terrain so you can see it.
I am having trouble with the toggling using a CallbackProperty. I went back to setting heightReference directly and it seemed to work fine.
I’ve found a way to get around this in my current code, but it seems like Cesium should support the ability to create a polygon that’s non-extruded, relativeToGround, and has perPositionHeight all at the same time. Does anyone know if there are plans to get this fixed in the future?
It should be supported. I went ahead an opened an issue, #6976. We may not be able to get to this right away, but if you could help by tracking down the error or providing a fix, contributions are greatly appreciated!