Improve descriptions and comments (https://github.com/o3de/o3de/pull/6428#discussion_r799207891, https://github.com/o3de/o3de/pull/6428#discussion_r799213620)

Signed-off-by: Santi Paprika <santi.gonzalez.cs@gmail.com>

Gems/Atom/Feature/Common/Assets/Materials/Types/EnhancedPBR.materialtype

@@ -1244,7 +1244,7 @@
                 {
                     "name": "distanceAttenuation",
                     "displayName": "    Distance Attenuation",
-                    "description": "Attenuation applied to hide artifacts due to low-res shadow maps (e.g. objects far to the camera when using directional lights or objects far to the light when using sphere/disk lights",
+                    "description": "Attenuation of the transmission effect, used to hide artifacts due to low-res shadow maps\nFor directional lights: attenuation proportional to the distance from the object to the camera.\nFor other light sources: attenuation proportional to the distance from the object to the light source.",
                     "type": "float",
                     "defaultValue": 0.5,
                     "min": 0.0,

Gems/Atom/Feature/Common/Assets/Materials/Types/Skin.materialtype

@@ -658,7 +658,7 @@
                 {
                     "name": "distanceAttenuation",
                     "displayName": "    Distance Attenuation",
-                    "description": "Attenuation applied to hide artifacts due to low-res shadow maps (e.g. objects far to the camera when using directional lights or objects far to the light when using sphere/disk lights",
+                    "description": "Attenuation of the transmission effect, used to hide artifacts due to low-res shadow maps\nFor directional lights: attenuation proportional to the distance from the object to the camera.\nFor other light sources: attenuation proportional to the distance from the object to the light source.",
                     "type": "float",
                     "defaultValue": 0.5,
                     "min": 0.0,

Gems/Atom/Feature/Common/Assets/ShaderLib/Atom/Features/PBR/BackLighting.azsli

@@ -72,9 +72,8 @@ float3 GetBackLighting(Surface surface, LightingData lightingData, float3 lightI
                 }
 
                 // Irradiance arround surface point. 
-                // Albedo at front (surface point) is used to approximate irradiance at the back of the object
+                // Albedo at front (surface point) is used to approximate irradiance at the back of the object (observation 4 in [Jimenez J. et al, 2010])
-                // See observation 4 in [Jimenez J. et al, 2010] 
+                // Increase angle of influence to smooth transition regions
-                // Increase angle of influence (angle(N,L) -> angle(N,L) + acos(transmissionNdLBias)) to smooth transition regions
                 float3 E = surface.albedo * saturate(lightingData.transmissionNdLBias + dot(-surface.normal, dirToLight));
 
                 // Transmission distance modulated by hardcoded constant C and the thickness exposed parameter (in this case modulating the distance traversed by the light inside the object)