Allow non-linear screen space error

[javagl]

^{This issue is triggered by this forum post}

Right now, the computation of the screen space error from the geometric error and the distance is linear, as in sse = geometricError / distance (with some more or less constant factors sprinkled in).

It could be a reasonable demand to use higher detail for things that are closer, taking the distance into account non-linearly. For example, sse = geometricError / pow(distance, someExponent), with someExponent being 1.0 by default, or 0.9 to give a higher detail to elements that are closer to the viewer.

_{This could be implemented trivially ("Just add someExponent to TilesetOptions and pass it along..."), but of course, if something like this is implemented, it should be offered in a more generic form. As such, this issue is only one special instance of all the thoughts and scenarios that I compressed into https://github.com/CesiumGS/cesium-native/issues/126 , but to have an overview of what could be possible with a few abstractions for the key concepts like "culling", "load priorization" etc., I'll mention it dedicatedly here.}

[kring]

CC https://github.com/CesiumGS/cesium-unreal/issues/323 I'm skeptical this would give good results, but it's simple enough to try so might as well give it a shot.

[pjcozzi]

We did something like this in CesiumJS awhile back for fog:

In Cesium, the fog is a blend of the atmosphere color and the terrain on the horizon. Terrain tiles that would be partially in fog will have their screen-space error increased, allowing lower-resolution terrain to be rendered. Terrain tiles that are completely in the fog will be culled completely or not even requested.

https://cesium.com/blog/2015/11/12/fog/

Just FYI, not for or against it.

[a519894574]

这个问题是由这个论坛帖子触发的

现在，根据几何误差和距离计算屏幕空间误差是线性的，如sse = geometricError / distance（撒有一些或多或少的常数因子）。

考虑到_非线性距离，对__较近的事物使用__更高的_细节可能是合理的要求。例如，默认值为 1.0，或 0.9 为更靠近查看者的元素提供更高的细节。____sse = geometricError / pow(distance, someExponent)``someExponent

这可以简单地实现（“只需添加someExponent并TilesetOptions传递它......”），但是当然，如​​果实现了这样的东西，它应该以更通用的形式提供。因此，这个问题只是我压缩到#126中的所有想法和场景的一个特殊实例，但为了概述通过对“剔除”、“加载优先级”等关键概念进行一些抽象可能实现的功能等等，这里专门提一下。

cesium for unreal c ++ who change?