Add feature to knock out highlights and reflections depending on pigment transparency.

Author: c-lipka

changes.txt

@@ -49,6 +49,10 @@ Prior to the release of 3.7.1, the following items still need urgent attention:
 New Features
 ------------
 
+- A new finish parameter, `use_alpha BOOL`, has been added. If set to `on`,
+  pigment transparency suppresses highlights and reflections. The default
+  setting is `off`.
+
 - A new pattern, `potential`, has been added to define a pattern based on the
   potential field of a blob or isosurface object.
 

source/base/version.h

@@ -45,7 +45,7 @@
 #define OFFICIAL_VERSION_STRING "3.7.1"
 #define OFFICIAL_VERSION_NUMBER 371
 
-#define POV_RAY_PRERELEASE "alpha"
+#define POV_RAY_PRERELEASE "x.knockout.8881807"
 
 #if (POV_RAY_IS_AUTOBUILD == 1) && ((POV_RAY_IS_OFFICIAL == 1) || (POV_RAY_IS_SEMI_OFFICIAL == 1))
 #ifdef POV_RAY_PRERELEASE

source/core/material/texture.cpp

@@ -1187,6 +1187,8 @@ FINISH *Create_Finish()
     New->SubsurfaceTranslucency.Clear();
     New->SubsurfaceAnisotropy.Clear();
 
+    New->AlphaKnockout = false;
+
     return(New);
 }
 

source/core/material/texture.h

@@ -132,6 +132,7 @@ struct Finish_Struct
     SNGL Reflect_Metallic; // MBP
     int Conserve_Energy;  // added by NK Dec 19 1999
     bool UseSubsurface;   // whether to use subsurface light transport
+    bool AlphaKnockout;   // whether pigment alpha knocks out finish effects
 };
 
 

source/core/render/trace.cpp

@@ -860,6 +860,9 @@ void Trace::ComputeLightedTexture(MathColour& resultColour, ColourChannel& resul
             else
                 att = layCol.Opacity();
 
+            if (layer->Finish->AlphaKnockout)
+                listWNRX->back().reflec *= att;
+
             // now compute the BRDF or BSSRDF contribution
             tmpCol.Clear();
 
@@ -964,7 +967,12 @@ void Trace::ComputeLightedTexture(MathColour& resultColour, ColourChannel& resul
             // (We don't need to do this for (non-radiosity) rays during pretrace, as it does not affect radiosity sampling)
             if(!ray.IsPretraceRay())
             {
-                if((layer->Finish->Diffuse != 0.0) || (layer->Finish->DiffuseBack != 0.0) || (layer->Finish->Specular != 0.0) || (layer->Finish->Phong != 0.0))
+                if (((layer->Finish->Diffuse     != 0.0) ||
+                     (layer->Finish->DiffuseBack != 0.0) ||
+                     (layer->Finish->Specular    != 0.0) ||
+                     (layer->Finish->Phong       != 0.0)) &&
+                    ((!layer->Finish->AlphaKnockout) ||
+                     (att != 0.0)))
                 {
                     MathColour classicContribution;
 
@@ -1643,18 +1651,22 @@ void Trace::ComputeOneDiffuseLight(const LightSource &lightsource, const Vector3
             // surface-only diffuse term, they should use layered textures.
             ComputeDiffuseColour(finish, lightsourceray.Direction, eye.Direction, layer_normal, tmpCol, lightcolour, layer_pigment_colour, relativeIor, attenuation, backside);
 
+        MathColour tempLightColour = (finish->AlphaKnockout ? lightcolour * attenuation : lightcolour);
+
         // NK rad - don't compute highlights for radiosity gather rays, since this causes
         // problems with colors being far too bright
         // don't compute highlights for diffuse backside illumination
         if((lightsource.Light_Type != FILL_LIGHT_SOURCE) && !eye.IsRadiosityRay() && !backside) // TODO FIXME radiosity - is this really the right way to do it (speaking of realism)?
         {
             if(finish->Phong > 0.0)
             {
-                ComputePhongColour(finish, lightsourceray.Direction, eye.Direction, layer_normal, tmpCol, lightcolour, layer_pigment_colour, relativeIor);
+                ComputePhongColour (finish, lightsourceray.Direction, eye.Direction, layer_normal, tmpCol,
+                                    tempLightColour, layer_pigment_colour, relativeIor);
             }
 
             if(finish->Specular > 0.0)
-                ComputeSpecularColour(finish, lightsourceray.Direction, -eye.Direction, layer_normal, tmpCol, lightcolour, layer_pigment_colour, relativeIor);
+                ComputeSpecularColour (finish, lightsourceray.Direction, -eye.Direction, layer_normal, tmpCol,
+                                       tempLightColour, layer_pigment_colour, relativeIor);
         }
 
         if(finish->Irid > 0.0)

source/parser/parser_materials.cpp

@@ -2632,6 +2632,10 @@ void Parser::Parse_Finish (FINISH **Finish_Ptr)
             Parse_End();
         END_CASE
 
+        CASE (USE_ALPHA_TOKEN)
+            New->AlphaKnockout = ((int) Allow_Float(1.0) != 0);
+        END_CASE
+
         OTHERWISE
             UNGET
             EXIT

unix/VERSION

@@ -1 +1 @@
-3.7.1-alpha
+3.7.1-x.knockout.8881807