Blend probe importance for reflection probes makes absolutely zero sense in URP

[sacb0y]

While i can deal with blend probes not being fully functional and “blending” the use of importance to choose which reflection probe is used is completely bonkers.

I use anchor points and importance to manage the rendering of my characters and objects. Especially when i need many objects to render similarly. But for some reason even though reflection probes don’t blend, their influence extends farther than their collision volume.

So take this scene…

There are three reflection probes here…

The center one is a larger volume, while the red and blue probes are smaller.

The green cube above is the anchor point for the reflective sphere in the middle.

The red and blue reflection probes have a higher importance than the center one.

So lets move the green cube to the left.

Note that now it is red below the reflective cube

But is the green cube in the volume?

No. Lets check the spheres blend probe influence…

The red probe has almost zero influence when really it shouldn’t even be on this list at all.

If blend probes do not blend, why do they have influence at all outside of their volumes, and why is this not adjustable? Infact i even tried going into debug mode and lowering the “blend distance” there but nothing changes.

This gets worse with more complex scenarios

Here the sphere is blue

Yet it is not in either box, and even moving it well into the red probe box still keeps it blue (even though the have the same importance too).

This is maddening behavior, cause it means the influence is entirely unpredictable. This might be fine with actually blending probes but as it is it’s infuriating.

[Jebtor]

Hey,

First of all, I understand you confusion and frustration. I hope to bring some improvements to this soon. Here is some information that will hopefully explain the behavior you are seeing:

The reflection probe selection is identical to built-in. This means the documentation here applies (with the exception of blending). The only difference is that URP does not support blending between active probes. URP will always take the first probe at slot 0.

The reason why you see probes being activated outside their volume is because in built-in probes blend outwards. As soon as an object touches the volume it will be weighted in. I expect that the green cube plus the bounds of the sphere will be touching the volumes. Blend distance is not being used here at all, it is only used in built-in deferred rendering. This is also why it is not visible in the inspector.

One thing you could try is to set Reflection Probes to “Simple” on your MeshRenderer. This will the probe selection know you only intend to use a single probe.