Add optional depth fog to Environment

[scriptsengineer]

Continuation of the PR created as a draft here #66030

Summary:

• fog_mode: Adds option to choose between normal fog called here exponential and new fog called fog depth, fog depth used in a specialization constant in the relevant scene shaders. This addresses the performance caveat discussed in Automatically fade to Z far in environment depth fog #55388 by ensuring that when only exponential fog is used, the branch is never present in the compiled program. It is not possible to use quadratic fog exclusively at the shader level in this implementation, but you can set the parameters of the environment such that the exponential fog density is 0 while still having quadratic fog if you must have no exponential fog at all. During project conversion, this property should be set to true if fog was enabled, the new fog density should be set to 0, and the sky affect scale should also be set to 0.
  fog_depth_curve: Same as in Godot 3.x
• fog_density: In fog exponential it continues with its same functionality, but in fog depth it replaces the alpha value of fog_depth_color in Godot 3.x. Project conversion should take the fog color's alpha and put it in this property instead.
• fog_depth_begin: Same as in Godot 3.x
• fog_depth_end: Same as in Godot 3.x

✅ Merged successfully

✅ Removed unnecessary pads

✅ Added enum option in the environment inspector

✅ Added conditional in shader to execute correct fog mode
I was wondering if there is a better way to define this if
scene.glsl:

#ifndef DISABLE_FOG_DEPTH
	if (scene_data.fog_mode == 1) {
		float fog_far = scene_data.fog_depth_end > 0.0 ? scene_data.fog_depth_end : scene_data.z_far;
		float fog_z = smoothstep(scene_data.fog_depth_begin, fog_far, length(vertex));

		float fog_quad_amount = pow(fog_z, scene_data.fog_depth_curve) * scene_data.fog_density;
		fog_amount = fog_quad_amount;
	}
#else
	if (scene_data.fog_mode == 0) {
		fog_amount = 1 - exp(min(0.0, -length(vertex) * scene_data.fog_density));
	}

✅ Possible to add negative values in fog begin

godot.windows.editor.x86_64_cGJmj07bao.mp4

[AThousandShips]

any chance this gets merged? is this a technical issue or a design consideration?

When it has been reviewed, we are in feature freeze right now so it won't be evaluated until after 4.2 has been released, please have patience 🙂

Please add your opinions to:

• Allow controlling fog intensity with traditional start/end distance and curve in Godot 4 godot-proposals#4619

This is not the place for these points

[clayjohn]

Great work! This is looking really good. I tested locally and this appears to work well on the RD backends. Its currently broken in the compatibility backend but I have left comments on how to fix that.

I think overall this is very close to being ready to merge, but I have left a few suggestions for things that are needed to get it fully ready.

When you update I suggest that you also rebase to squish the commits together to get this ready for merging as I suspect we should be able to merge pretty quickly after you update to address my comments.

[scriptsengineer]

Tested locally on Linux, I get these errors in the terminal after merging this PR, when opening the project manager with OpenGL:

Fixed

[scriptsengineer]

@clayjohn There is a problem with compatibility mode, i need help with this
Before this PR

After this PR

[HybridEidolon]

@clayjohn There is a problem with compatibility mode, i need help with this

The uniforms in the UBO may be misaligned to std140 alignment in the compatibility shaders.

[scriptsengineer]

The uniforms in the UBO may be misaligned to std140 alignment in the compatibility shaders.

Fixed

[akien-mga]

Thanks @HybridEidolon and @scriptsengineer for this amazing joint first contribution! 🎉 🥇

[ghost]

I am testing out the new depth fog in 4.3 dev 5. It seems to be working well with a procedural sky.

Is there a way to get the depth fog to blend with a sky box?

Or a way to get a sky box (or I suppose any other object) excluded from the depth fog?

[clayjohn]

I am testing out the new depth fog in 4.3 dev 5. It seems to be working well with a procedural sky.

Is there a way to get the depth fog to blend with a sky box?

Yes, using the atmospheric perspective setting

Or a way to get a sky box (or I suppose any other object) excluded from the depth fog?

For regular objects, there is a flag to ignore fog in their material. For sky materials, I don't think we expose the flag, but we probably could

[Calinou]

For sky materials, I don't think we expose the flag, but we probably could

There's a Sky Affect property you can adjust in the fog properties. Setting it to 0 will prevent fog from affecting the sky at all, regardless of which sky material it currently is.

Is there a way to get the depth fog to blend with a sky box?

Fog aerial perspective can be used for this, but it'll be much more effective if #89995 is merged.

[ghost]

I am testing out the new depth fog in 4.3 dev 5. It seems to be working well with a procedural sky.
Is there a way to get the depth fog to blend with a sky box?

Yes, using the atmospheric perspective setting

I've attached three images using all three types of sky materials. Are these the expected results?

[ghost]

I'd like to suggest that "atmospheric perspective" will be better for users than "aerial perspective". The terms seem to be interchangeable.

Or possibly "Background Blend" since that is a more direct description of what it is actually doing.

[Calinou]

I've attached three images using all three types of sky materials. Are these the expected results?

Yes. If you want more precise fading, you need something like #89995 which isn't merged (and may require a different approach as per the comments).

I'd like to suggest that "atmospheric perspective" will be better for users than "aerial perspective". The terms seem to be interchangeable.

We can't rename existing properties without breaking compatibility with existing projects, so we should stick to aerial perspective for the time being.

If we add a dedicated background blend property, then it should have its own name that can't be mistaken for aerial perspective.

[ghost]

Thanks for the response. The new depth fog is a good change.

Yes. If you want more precise fading, you need something like #89995 which isn't merged (and may require a different approach as per the comments).

I'm not sure if I need more precision, exactly, but some way to blend the horizon and the terrain together while also having an unfogged sky is what I ultimately need. I may be able to get the results I want with what you've already done. The end result can be artistically correct instead of physically correct and I'm still happy.

The help text for aerial perspective says the fog's color will be blended with the "color of the background sky". Is it then blending to a single average color of the sky, or is it using the average of the color at the horizon of the sky, or ?

[Calinou]

The help text for aerial perspective says the fog's color will be blended with the "color of the background sky". Is it then blending to a single average color of the sky, or is it using the average of the color at the horizon of the sky, or ?

Aerial perspective blends the fog color with the (blurred) radiance map of the sky. The radiance maps is what's used for material reflections when no GI method is used and there are no reflection probes nearby.

If you set Fog > Sky Affect below 1.0, the appearance of aerial perspective fog won't change (I just tested).

[ghost]

Aerial perspective blends the fog color with the (blurred) radiance map of the sky. The radiance maps is what's used for material reflections when no GI method is used and there are no reflection probes nearby.

After some experimentation I'm getting great results. Thanks for all the effort that went into this.

If you set Fog > Sky Affect below 1.0, the appearance of aerial perspective fog won't change (I just tested).

What I'm seeing is if I set Aerial Perspective to 1.0, then the Sky Affect value has no effect. Not quite the opposite of what you said, but I wonder if that was a typo?

Here is a screenshot of what I'm working on so you can see how the depth fog is working.

[ghost]

One thing I just noticed in 4.3 dev 5 is that if I enable "Volumetric Fog" the fog effect fills the entire screen. I'd file a separate issue, but I think it must be related.

[RichardEllicott]

anyone know if this is this gonna be in Godot 4.3?

[Calinou]

anyone know if this is this gonna be in Godot 4.3?

It's already implemented as of 4.3.beta3 🙂

Set the fog mode to Depth in the Environment properties.

[RichardEllicott]

anyone know if this is this gonna be in Godot 4.3?

It's already implemented as of 4.3.beta3 🙂

Set the fog mode to Depth in the Environment properties.

thanks man that is epic news for me, maybe i'll just jump to beta