Merge pull request #49340 from Calinou/decal-modulate-affect-emission

Make Decal's `modulate` property affect emission color as well

2 files changed, 11 insertions, 8 deletions

diff --git a/doc/classes/Decal.xml b/doc/classes/Decal.xml
index b86104a5e3..3322ab4c66 100644
--- a/doc/classes/Decal.xml
+++ b/doc/classes/Decal.xml
@@ -58,7 +58,7 @@
 	</methods>
 	<members>
 		<member name="albedo_mix" type="float" setter="set_albedo_mix" getter="get_albedo_mix" default="1.0">
-			Blends the albedo [Color] of the decal with albedo [Color] of the underlying mesh.
+			Blends the albedo [Color] of the decal with albedo [Color] of the underlying mesh. This can be set to [code]0.0[/code] to create a decal that only affects normal or ORM. In this case, an albedo texture is still required as its alpha channel will determine where the normal and ORM will be overridden. See also [member modulate].
 		</member>
 		<member name="cull_mask" type="int" setter="set_cull_mask" getter="get_cull_mask" default="1048575">
 			Specifies which [member VisualInstance3D.layers] this decal will project on. By default, Decals affect all layers. This is used so you can specify which types of objects receive the Decal and which do not. This is especially useful so you can ensure that dynamic objects don't accidentally receive a Decal intended for the terrain under them.
@@ -70,22 +70,23 @@
 			If [code]true[/code], decals will smoothly fade away when far from the active [Camera3D] starting at [member distance_fade_begin]. The Decal will fade out over [member distance_fade_begin] + [member distance_fade_length], after which it will be culled and not sent to the shader at all. Use this to reduce the number of active Decals in a scene and thus improve performance.
 		</member>
 		<member name="distance_fade_length" type="float" setter="set_distance_fade_length" getter="get_distance_fade_length" default="10.0">
-			The distance over which the Decal fades (in 3D units). The Decal becomes slowly more transparent over this distance and is completely invisible at the end.
+			The distance over which the Decal fades (in 3D units). The Decal becomes slowly more transparent over this distance and is completely invisible at the end. Higher values result in a smoother fade-out transition, which is more suited when the camera moves fast.
 		</member>
 		<member name="emission_energy" type="float" setter="set_emission_energy" getter="get_emission_energy" default="1.0">
-			Energy multiplier for the emission texture. This will make the decal emit light at a higher intensity.
+			Energy multiplier for the emission texture. This will make the decal emit light at a higher or lower intensity, independently of the albedo color. See also [member modulate].
 		</member>
 		<member name="extents" type="Vector3" setter="set_extents" getter="get_extents" default="Vector3(1, 1, 1)">
 			Sets the size of the [AABB] used by the decal. The AABB goes from [code]-extents[/code] to [code]extents[/code].
 		</member>
 		<member name="lower_fade" type="float" setter="set_lower_fade" getter="get_lower_fade" default="0.3">
-			Sets the curve over which the decal will fade as the surface gets further from the center of the [AABB]. Only positive values are valid (negative values will be clamped to [code]0.0[/code]).
+			Sets the curve over which the decal will fade as the surface gets further from the center of the [AABB]. Only positive values are valid (negative values will be clamped to [code]0.0[/code]). See also [member upper_fade].
 		</member>
 		<member name="modulate" type="Color" setter="set_modulate" getter="get_modulate" default="Color(1, 1, 1, 1)">
-			Changes the [Color] of the Decal by multiplying it with this value.
+			Changes the [Color] of the Decal by multiplying the albedo and emission colors with this value. The alpha component is only taken into account when multiplying the albedo color, not the emission color. See also [member emission_energy] and [member albedo_mix] to change the emission and albedo intensity independently of each other.
 		</member>
 		<member name="normal_fade" type="float" setter="set_normal_fade" getter="get_normal_fade" default="0.0">
 			Fades the Decal if the angle between the Decal's [AABB] and the target surface becomes too large. A value of [code]0[/code] projects the Decal regardless of angle, a value of [code]1[/code] limits the Decal to surfaces that are nearly perpendicular.
+			[b]Note:[/b] Setting [member normal_fade] to a value greater than [code]0.0[/code] has a small performance cost due to the added normal angle computations.
 		</member>
 		<member name="texture_albedo" type="Texture2D" setter="set_texture" getter="get_texture">
 			[Texture2D] with the base [Color] of the Decal. Either this or the [member texture_emission] must be set for the Decal to be visible. Use the alpha channel like a mask to smoothly blend the edges of the decal with the underlying object.
@@ -98,13 +99,15 @@
 		<member name="texture_normal" type="Texture2D" setter="set_texture" getter="get_texture">
 			[Texture2D] with the per-pixel normal map for the decal. Use this to add extra detail to decals.
 			[b]Note:[/b] Unlike [BaseMaterial3D] whose filter mode can be adjusted on a per-material basis, the filter mode for [Decal] textures is set globally with [member ProjectSettings.rendering/textures/decals/filter].
+			[b]Note:[/b] Setting this texture alone will not result in a visible decal, as [member texture_albedo] must also be set. To create a normal-only decal, load an albedo texture into [member texture_albedo] and set [member albedo_mix] to [code]0.0[/code]. The albedo texture's alpha channel will be used to determine where the underlying surface's normal map should be overridden (and its intensity).
 		</member>
 		<member name="texture_orm" type="Texture2D" setter="set_texture" getter="get_texture">
 			[Texture2D] storing ambient occlusion, roughness, and metallic for the decal. Use this to add extra detail to decals.
 			[b]Note:[/b] Unlike [BaseMaterial3D] whose filter mode can be adjusted on a per-material basis, the filter mode for [Decal] textures is set globally with [member ProjectSettings.rendering/textures/decals/filter].
+			[b]Note:[/b] Setting this texture alone will not result in a visible decal, as [member texture_albedo] must also be set. To create a ORM-only decal, load an albedo texture into [member texture_albedo] and set [member albedo_mix] to [code]0.0[/code]. The albedo texture's alpha channel will be used to determine where the underlying surface's ORM map should be overridden (and its intensity).
 		</member>
 		<member name="upper_fade" type="float" setter="set_upper_fade" getter="get_upper_fade" default="0.3">
-			Sets the curve over which the decal will fade as the surface gets further from the center of the [AABB]. Only positive values are valid (negative values will be clamped to [code]0.0[/code]).
+			Sets the curve over which the decal will fade as the surface gets further from the center of the [AABB]. Only positive values are valid (negative values will be clamped to [code]0.0[/code]). See also [member lower_fade].
 		</member>
 	</members>
 	<constants>
diff --git a/servers/rendering/renderer_rd/shaders/scene_forward_clustered.glsl b/servers/rendering/renderer_rd/shaders/scene_forward_clustered.glsl
index 5947fc5351..360ece7f32 100644
--- a/servers/rendering/renderer_rd/shaders/scene_forward_clustered.glsl
+++ b/servers/rendering/renderer_rd/shaders/scene_forward_clustered.glsl
@@ -947,9 +947,9 @@ void fragment_shader(in SceneData scene_data) {
 				if (decals.data[decal_index].emission_rect != vec4(0.0)) {
 					//emission is additive, so its independent from albedo
 					if (sc_decal_use_mipmaps) {
-						emission += textureGrad(sampler2D(decal_atlas_srgb, decal_sampler), uv_local.xz * decals.data[decal_index].emission_rect.zw + decals.data[decal_index].emission_rect.xy, ddx * decals.data[decal_index].emission_rect.zw, ddy * decals.data[decal_index].emission_rect.zw).xyz * decals.data[decal_index].emission_energy * fade;
+						emission += textureGrad(sampler2D(decal_atlas_srgb, decal_sampler), uv_local.xz * decals.data[decal_index].emission_rect.zw + decals.data[decal_index].emission_rect.xy, ddx * decals.data[decal_index].emission_rect.zw, ddy * decals.data[decal_index].emission_rect.zw).xyz * decals.data[decal_index].modulate.rgb * decals.data[decal_index].emission_energy * fade;
 					} else {
-						emission += textureLod(sampler2D(decal_atlas_srgb, decal_sampler), uv_local.xz * decals.data[decal_index].emission_rect.zw + decals.data[decal_index].emission_rect.xy, 0.0).xyz * decals.data[decal_index].emission_energy * fade;
+						emission += textureLod(sampler2D(decal_atlas_srgb, decal_sampler), uv_local.xz * decals.data[decal_index].emission_rect.zw + decals.data[decal_index].emission_rect.xy, 0.0).xyz * decals.data[decal_index].modulate.rgb * decals.data[decal_index].emission_energy * fade;
 					}
 				}
 			}