0024344: TKOpenGl - only front side is lighted within Phong GLSL program

diff --git a/src/Shaders/PhongShading.fs b/src/Shaders/PhongShading.fs
index 1b0779f..665f83d 100644 (file)
--- a/src/Shaders/PhongShading.fs
+++ b/src/Shaders/PhongShading.fs
@@ -46,13 +46,14 @@ void pointLight (in int  theId,
 
   vec3 aHalf = normalize (aLight + theView);
 
-  float aNdotL = max (0.0, dot (theNormal, aLight));
-  float aNdotH = max (0.0, dot (theNormal, aHalf ));
+  vec3  aFaceSideNormal = gl_FrontFacing ? theNormal : -theNormal;
+  float aNdotL = max (0.0, dot (aFaceSideNormal, aLight));
+  float aNdotH = max (0.0, dot (aFaceSideNormal, aHalf ));
 
   float aSpecl = 0.0;
   if (aNdotL > 0.0)
   {
-    aSpecl = pow (aNdotH, occFrontMaterial_Shininess());
+    aSpecl = pow (aNdotH, gl_FrontFacing ? occFrontMaterial_Shininess() : occBackMaterial_Shininess());
   }
 
   Diffuse  += occLight_Diffuse  (theId).rgb * aNdotL * anAtten;
@@ -71,13 +72,15 @@ void directionalLight (in int  theId,
   }
 
   vec3 aHalf = normalize (aLight + theView);
-  float aNdotL = max (0.0, dot (theNormal, aLight));
-  float aNdotH = max (0.0, dot (theNormal, aHalf ));
+
+  vec3  aFaceSideNormal = gl_FrontFacing ? theNormal : -theNormal;
+  float aNdotL = max (0.0, dot (aFaceSideNormal, aLight));
+  float aNdotH = max (0.0, dot (aFaceSideNormal, aHalf ));
 
   float aSpecl = 0.0;
   if (aNdotL > 0.0)
   {
-    aSpecl = pow (aNdotH, occFrontMaterial_Shininess());
+    aSpecl = pow (aNdotH, gl_FrontFacing ? occFrontMaterial_Shininess() : occBackMaterial_Shininess());
   }
 
   Diffuse  += occLight_Diffuse  (theId).rgb * aNdotL;
@@ -111,9 +114,12 @@ vec4 computeLighting (in vec3 theNormal,
     }
   }
 
-  return vec4 (Ambient,  1.0) * occFrontMaterial_Ambient()
-       + vec4 (Diffuse,  1.0) * occFrontMaterial_Diffuse()
-       + vec4 (Specular, 1.0) * occFrontMaterial_Specular();
+  vec4 aMaterialAmbient  = gl_FrontFacing ? occFrontMaterial_Ambient()  : occBackMaterial_Ambient();
+  vec4 aMaterialDiffuse  = gl_FrontFacing ? occFrontMaterial_Diffuse()  : occBackMaterial_Diffuse();
+  vec4 aMaterialSpecular = gl_FrontFacing ? occFrontMaterial_Specular() : occBackMaterial_Specular();
+  return vec4 (Ambient,  1.0) * aMaterialAmbient
+       + vec4 (Diffuse,  1.0) * aMaterialDiffuse
+       + vec4 (Specular, 1.0) * aMaterialSpecular;
 }
 
 //! Entry point to the Fragment Shader

diff --git a/tests/v3d/glsl/phong_sides b/tests/v3d/glsl/phong_sides
new file mode 100644 (file)
index 0000000..6d7fe78
--- /dev/null
+++ b/tests/v3d/glsl/phong_sides
@@ -0,0 +1,37 @@
+puts "========"
+puts "Per-pixel lighting using GLSL program (Phong shading), check lighting of back faces"
+puts "========"
+
+# create box
+box b 1 2 3
+explode b F
+
+# draw box
+vinit View1
+vclear
+vsetdispmode 1
+vaxo
+vdisplay b_1 b_2
+vfit
+vrotate 0.2 0.0 0.0
+
+# take snapshot with fixed pipeline
+vdump $::imagedir/${::casename}_OFF.png
+set aColorB [vreadpixel 150 150 rgb name]
+set aColorF [vreadpixel 250 250 rgb name]
+if { "$aColorB" != "$aColorF"} {
+  puts "Error: front/back colors are different!"
+}
+set aColorFixed $aColorF
+
+# activate phong shader
+vshaderprog phong
+set aColorB [vreadpixel 150 150 rgb name]
+set aColorF [vreadpixel 250 250 rgb name]
+if { "$aColorB" != "$aColorF"} {
+  puts "Error: front/back colors are different!"
+}
+
+if { "$aColorF" != "$aColorFixed"} {
+  puts "Error: colors are different!"
+}