Eevee: Initial Separable Subsurface Scattering implementation.

How to use:
- Enable subsurface scattering in the render options.
- Add Subsurface BSDF to your shader.
- Check "Screen Space Subsurface Scattering" in the material panel options.

This initial implementation has a few limitations:
- only supports gaussian SSS.
- Does not support principled shader.
- The radius parameters is baked down to a number of samples and then put into an UBO. This means the radius input socket cannot be used. You need to tweak the default vector directly.
- The "texture blur" is considered as always set to 1

2 files changed, 14 insertions, 0 deletions

diff --git a/source/blender/makesrna/intern/rna_layer.c b/source/blender/makesrna/intern/rna_layer.c
index b92f06c97a5..ec2ff5f1741 100644
--- a/source/blender/makesrna/intern/rna_layer.c
+++ b/source/blender/makesrna/intern/rna_layer.c
@@ -367,6 +367,7 @@ RNA_LAYER_ENGINE_EEVEE_GET_SET_FLOAT(volumetric_light_clamp)
 RNA_LAYER_ENGINE_EEVEE_GET_SET_BOOL(volumetric_shadows)
 RNA_LAYER_ENGINE_EEVEE_GET_SET_INT(volumetric_shadow_samples)
 RNA_LAYER_ENGINE_EEVEE_GET_SET_BOOL(volumetric_colored_transmittance)
+RNA_LAYER_ENGINE_EEVEE_GET_SET_BOOL(sss_enable)
 RNA_LAYER_ENGINE_EEVEE_GET_SET_BOOL(ssr_refraction)
 RNA_LAYER_ENGINE_EEVEE_GET_SET_BOOL(ssr_enable)
 RNA_LAYER_ENGINE_EEVEE_GET_SET_BOOL(ssr_halfres)
@@ -1195,6 +1196,14 @@ static void rna_def_scene_layer_engine_settings_eevee(BlenderRNA *brna)
 	RNA_def_property_flag(prop, PROP_CONTEXT_UPDATE);
 	RNA_def_property_update(prop, NC_SCENE | ND_LAYER_CONTENT, "rna_SceneLayerEngineSettings_update");
 
+	/* Screen Space Subsurface Scattering */
+	prop = RNA_def_property(srna, "sss_enable", PROP_BOOLEAN, PROP_NONE);
+	RNA_def_property_boolean_funcs(prop, "rna_LayerEngineSettings_Eevee_sss_enable_get",
+	                               "rna_LayerEngineSettings_Eevee_sss_enable_set");
+	RNA_def_property_ui_text(prop, "Subsurface Scattering", "Enable screen space subsurface scattering");
+	RNA_def_property_flag(prop, PROP_CONTEXT_UPDATE);
+	RNA_def_property_update(prop, NC_SCENE | ND_LAYER_CONTENT, "rna_SceneLayerEngineSettings_update");
+
 	/* Screen Space Reflection */
 	prop = RNA_def_property(srna, "ssr_enable", PROP_BOOLEAN, PROP_NONE);
 	RNA_def_property_boolean_funcs(prop, "rna_LayerEngineSettings_Eevee_ssr_enable_get",
diff --git a/source/blender/makesrna/intern/rna_material.c b/source/blender/makesrna/intern/rna_material.c
index 7f23cd78779..a78ad4262ce 100644
--- a/source/blender/makesrna/intern/rna_material.c
+++ b/source/blender/makesrna/intern/rna_material.c
@@ -1877,6 +1877,11 @@ void RNA_def_material(BlenderRNA *brna)
 	RNA_def_property_ui_text(prop, "Screen Space Refraction", "Use raytraced screen space refractions");
 	RNA_def_property_update(prop, 0, "rna_Material_draw_update");
 
+	prop = RNA_def_property(srna, "use_screen_subsurface", PROP_BOOLEAN, PROP_NONE);
+	RNA_def_property_boolean_sdna(prop, NULL, "blend_flag", MA_BL_SS_SUBSURFACE);
+	RNA_def_property_ui_text(prop, "Screen Space Subsurface Scattering", "Use post process subsurface scattering");
+	RNA_def_property_update(prop, 0, "rna_Material_draw_update");
+
 	prop = RNA_def_property(srna, "refraction_depth", PROP_FLOAT, PROP_DISTANCE);
 	RNA_def_property_float_sdna(prop, NULL, "refract_depth");
 	RNA_def_property_range(prop, 0.0f, FLT_MAX);