Opacity of SSR unaffected by material roughness

[aaandreeew]

Godot version

4.0 beta1

System information

Windows 10 (x86_64), Vulkan, Intel Core i5-8265U with UHD Graphics 620 (31.0.101.2111)

Issue description

The roughness of a material does not affect the opacity of screen space reflections seen in the material. This means that a material with a roughness of 1.0 and metallic of 0.0 will still have obvious reflections.

I expected that these parameters would produce a completely matte material, but I can't make any completely matte materials at all. However, reflections from VoxelGI nodes or SDFGI do consider roughness for reflection opacity, and a roughness of 1.0 will produce a completely matte material.

Screen Space Reflections have equal opacity on 3 floor materials with metallic 0.0 and roughness 1.0, 0.5 and 0.0 left to right

Comparison between VoxelGI reflections (left) and SSR (right). Roughnesses are 1.0, 0.2 and 0.0 left to right.

I think SDFGI behaves correctly too, but I am experiencing a separate visual bug with SDFGI, hence I haven't shown it.

This is apparent in another sample scene with more realistic materials. The ground material has a roughness of 1.0. This issue is ruining any prospects of a realistic scene for me.

SSR in different scene with proper PBR materials — reflections abound

I believe this is the same kind of issue as #49402, which was reported for Godot 3.2.2 and was apparently fixed in the master branch according to #25112, the issue #49402 was merged into. I am still posting this because Vulkan is now being implemented instead of GLES 3 and this bug may be specific to the graphical problems I've experienced with Intel inegrated graphics.

Steps to reproduce

1. Create a Node3D containing a ground plane MeshInstance3D and box MeshInstance3D.
2. Create a material (StandardMaterial3D or ORMMaterial3D) with metallic = 0.0 and roughness = 1.0 and apply it to the ground mesh. The albedo doesn't matter.
3. Enable SSR in a WorldEnvironment node, increasing the Max Steps value to improve visibility.

Minimal reproduction project

ssr_opacity_roughness_bug.zip (for Godot 4.0 beta 1)

[aaandreeew]

Sorry, I pressed the wrong button :|

[Calinou]

Related to #61930 (see its fix #65594).

[josefkaragoli]

Related to #61930 (see its fix #65594).

That was about a metallic value of 0 not showing any reflections, whilst this issue is about roughness value not having an effect on ssr.

[aaandreeew]

Woohoo!