Incorrect specular lighting

[CptPotato]

Godot version: 3.1 stable

Specular reflections of direct lights seem to be incorrect. At medium to low roughness values, the specular blob is pretty much invisible. Even on a completely black mesh.

I suspect that it's due to faulty energy conservation or some of the parameters are off. (currently there is material > specular and light > specular which both default to 0.5)

Here's a comparison with blender (left) and godot (right):

albedo 1.0, roughness 1.0:

albedo 0.5, roughness 1.0:

albedo 0.0 (-> specular only!), roughness 0.5:

As you can see the specular highlight is already too dark to be visible, even though the light source isn't all that dark.

Steps to reproduce:
Observe how specular blobs react to changes in the roughness value.

[CptPotato]

Looks like this is a regression somewhere between 3.0 and 3.1.

If I compare the two versions, 3.1 has a much fainter specular highlight than 3.0.

Here's what I noticed during some tests (this is only comparing specular lighting):

version	light > specular	material > metallic > specular	result (direct light)	result (environment light)
3.0	0.5 (default)	0.5 (default)	correct	correct
3.1	0.5 (default)	0.5 (default)	way too dark	(not sure)
3.1	1.0	1.0	correct	(seems correct)

[akien-mga]

Looks like this is a regression somewhere between 3.0 and 3.1.

Could you try some 3.1 alpha/beta/RC builds to narrow down when the regression happened? See https://downloads.tuxfamily.org/godotengine/3.1/

[akien-mga]

Is this better after #27898?

[CptPotato]

I'll give it a test later today.

[CptPotato]

Sorry for the delay. As far as I can tell it seems better. If I set the material property Metallic > Specular to 1 it looks very similar to the blender PBR reference.