shadowMap changes when panning around and zooming

I’ve been playing with few examples with the shadowMap recently and I observed this: If I generate a shadowMap, and then zoom or move around on the globe, the green and red areas seem to change.

For example, observe the green area in front of the start of the camera: it slowly disappears as I continue to zoom out.

You could also test it by yourself in the sandcastle here:


Is this a problem with the glsl, or it’s something related to the shadowMap itself? Any hints as to where I could fine tune this behavior?


is this the Helsing-Algorithm for visibility analysis ? I habe similar behaviour.



Hi Ruediger,

Yes, the sandcastle demo (linked in the post) I think is based around that algo. I wonder if it’s a general problem with the shadowMap or just the algo itself? Any pointers or insights you could share?



I think the problem is that the terrain-data/tile-data is changed, if you zoom-in/zoom-out or move.
Therefore the shadowMap is updated.

If you have a look at the displayed tiles, you can see this (Debug-Mode)


Interesting observation. Indeed, that could be the issue. Thank you for sharing your thoughts, Ruediger!