diff --git a/android/core/src/processing/opengl/FillShaderVertFull.glsl b/android/core/src/processing/opengl/FillShaderVertFull.glsl
index 5734b25bd..c9a79eb50 100644
--- a/android/core/src/processing/opengl/FillShaderVertFull.glsl
+++ b/android/core/src/processing/opengl/FillShaderVertFull.glsl
@@ -65,14 +65,12 @@ float spotFactor(vec3 lightPos, vec3 vertPos, vec3 lightNorm, float minCos, floa
 }
 
 float lambertFactor(vec3 lightDir, vec3 vecNormal) {
-  //return max(zero_float, dot(lightDir, vecNormal));
-  return abs(dot(lightDir, vecNormal));
+  return max(zero_float, dot(lightDir, vecNormal));
 }
 
 float blinnPhongFactor(vec3 lightDir, vec3 lightPos, vec3 vecNormal, float shine) {
   vec3 ldp = normalize(lightDir - lightPos);
-  //return pow(max(zero_float, dot(ldp, vecNormal)), shine);
-  return pow(abs(dot(ldp, vecNormal)), shine);
+  return pow(max(zero_float, dot(ldp, vecNormal)), shine);
 }
 
 void main() {
@@ -85,6 +83,12 @@ void main() {
   // Normal vector in eye coordinates
   vec3 ecNormal = normalize(normalMatrix * inNormal);
   
+  if (dot(-ecVertex, ecNormal) < 0) {
+    // If normal is away from camera, choose its opposite.
+    // If we add backface culling, this will be backfacing  
+    ecNormal *= -1;
+  }  
+  
   // Light calculations
   vec3 totalAmbient = vec3(0, 0, 0);
   vec3 totalDiffuse = vec3(0, 0, 0);
diff --git a/android/core/src/processing/opengl/FillShaderVertLit.glsl b/android/core/src/processing/opengl/FillShaderVertLit.glsl
index 02ee447a4..33d2360e7 100644
--- a/android/core/src/processing/opengl/FillShaderVertLit.glsl
+++ b/android/core/src/processing/opengl/FillShaderVertLit.glsl
@@ -62,14 +62,12 @@ float spotFactor(vec3 lightPos, vec3 vertPos, vec3 lightNorm, float minCos, floa
 }
 
 float lambertFactor(vec3 lightDir, vec3 vecNormal) {
-  //return max(zero_float, dot(lightDir, vecNormal));
-  return abs(dot(lightDir, vecNormal));
+  return max(zero_float, dot(lightDir, vecNormal));
 }
 
 float blinnPhongFactor(vec3 lightDir, vec3 lightPos, vec3 vecNormal, float shine) {
   vec3 ldp = normalize(lightDir - lightPos);
-  //return pow(max(zero_float, dot(ldp, vecNormal)), shine);
-  return pow(abs(dot(ldp, vecNormal)), shine);
+  return pow(max(zero_float, dot(ldp, vecNormal)), shine);
 }
 
 void main() {
@@ -82,6 +80,12 @@ void main() {
   // Normal vector in eye coordinates
   vec3 ecNormal = normalize(normalMatrix * inNormal);
   
+  if (dot(-ecVertex, ecNormal) < 0) {
+    // If normal is away from camera, choose its opposite.
+    // If we add backface culling, this will be backfacing  
+    ecNormal *= -1;
+  }
+  
   // Light calculations
   vec3 totalAmbient = vec3(0, 0, 0);
   vec3 totalDiffuse = vec3(0, 0, 0);
diff --git a/java/libraries/opengl/src/processing/opengl/FillShaderVertFull.glsl b/java/libraries/opengl/src/processing/opengl/FillShaderVertFull.glsl
index 5734b25bd..c9a79eb50 100644
--- a/java/libraries/opengl/src/processing/opengl/FillShaderVertFull.glsl
+++ b/java/libraries/opengl/src/processing/opengl/FillShaderVertFull.glsl
@@ -65,14 +65,12 @@ float spotFactor(vec3 lightPos, vec3 vertPos, vec3 lightNorm, float minCos, floa
 }
 
 float lambertFactor(vec3 lightDir, vec3 vecNormal) {
-  //return max(zero_float, dot(lightDir, vecNormal));
-  return abs(dot(lightDir, vecNormal));
+  return max(zero_float, dot(lightDir, vecNormal));
 }
 
 float blinnPhongFactor(vec3 lightDir, vec3 lightPos, vec3 vecNormal, float shine) {
   vec3 ldp = normalize(lightDir - lightPos);
-  //return pow(max(zero_float, dot(ldp, vecNormal)), shine);
-  return pow(abs(dot(ldp, vecNormal)), shine);
+  return pow(max(zero_float, dot(ldp, vecNormal)), shine);
 }
 
 void main() {
@@ -85,6 +83,12 @@ void main() {
   // Normal vector in eye coordinates
   vec3 ecNormal = normalize(normalMatrix * inNormal);
   
+  if (dot(-ecVertex, ecNormal) < 0) {
+    // If normal is away from camera, choose its opposite.
+    // If we add backface culling, this will be backfacing  
+    ecNormal *= -1;
+  }  
+  
   // Light calculations
   vec3 totalAmbient = vec3(0, 0, 0);
   vec3 totalDiffuse = vec3(0, 0, 0);
diff --git a/java/libraries/opengl/src/processing/opengl/FillShaderVertLit.glsl b/java/libraries/opengl/src/processing/opengl/FillShaderVertLit.glsl
index 02ee447a4..33d2360e7 100644
--- a/java/libraries/opengl/src/processing/opengl/FillShaderVertLit.glsl
+++ b/java/libraries/opengl/src/processing/opengl/FillShaderVertLit.glsl
@@ -62,14 +62,12 @@ float spotFactor(vec3 lightPos, vec3 vertPos, vec3 lightNorm, float minCos, floa
 }
 
 float lambertFactor(vec3 lightDir, vec3 vecNormal) {
-  //return max(zero_float, dot(lightDir, vecNormal));
-  return abs(dot(lightDir, vecNormal));
+  return max(zero_float, dot(lightDir, vecNormal));
 }
 
 float blinnPhongFactor(vec3 lightDir, vec3 lightPos, vec3 vecNormal, float shine) {
   vec3 ldp = normalize(lightDir - lightPos);
-  //return pow(max(zero_float, dot(ldp, vecNormal)), shine);
-  return pow(abs(dot(ldp, vecNormal)), shine);
+  return pow(max(zero_float, dot(ldp, vecNormal)), shine);
 }
 
 void main() {
@@ -82,6 +80,12 @@ void main() {
   // Normal vector in eye coordinates
   vec3 ecNormal = normalize(normalMatrix * inNormal);
   
+  if (dot(-ecVertex, ecNormal) < 0) {
+    // If normal is away from camera, choose its opposite.
+    // If we add backface culling, this will be backfacing  
+    ecNormal *= -1;
+  }
+  
   // Light calculations
   vec3 totalAmbient = vec3(0, 0, 0);
   vec3 totalDiffuse = vec3(0, 0, 0);