diff --git a/src/dump_image.cpp b/src/dump_image.cpp
index 32b4a69feb..ff5c8ca31f 100644
--- a/src/dump_image.cpp
+++ b/src/dump_image.cpp
@@ -921,6 +921,14 @@ void DumpImage::create_image()
   // for 3d, outward normals on all 6 faces
 
   if (gridflag) {
+
+    // reset lighting for flat surfaces to make them brighter
+ 
+    image->ambientColor[0] = image->ambientColor[1] = image->ambientColor[2] = 0.9;
+    image->keyLightColor[0] = image->keyLightColor[1] = image->keyLightColor[2] = 0.3;
+    image->fillLightColor[0] = image->fillLightColor[1] = image->fillLightColor[2] = 0.3;
+    image->backLightColor[0] = image->backLightColor[1] = image->backLightColor[2] = 0.3;
+
     int n = 0;
     if (domain->dimension == 2) {
       for (int iy = nylo_in; iy <= nyhi_in; iy++)
@@ -956,6 +964,13 @@ void DumpImage::create_image()
             image->draw_triangle(gcorners[4],gcorners[7],gcorners[6],color);
           }
     }
+
+    // restore lighting for curved objects
+
+    image->ambientColor[0] = image->ambientColor[1] = image->ambientColor[2] = 0.0;
+    image->keyLightColor[0] = image->keyLightColor[1] = image->keyLightColor[2] = 0.9;
+    image->fillLightColor[0] = image->fillLightColor[1] = image->fillLightColor[2] = 0.45;
+    image->backLightColor[0] = image->backLightColor[1] = image->backLightColor[2] = 0.9;
   }
 
   // render atoms that are lines
diff --git a/src/image.cpp b/src/image.cpp
index 8c503adf92..716104d009 100644
--- a/src/image.cpp
+++ b/src/image.cpp
@@ -815,26 +815,34 @@ void Image::draw_triangle(double *x, double *y, double *z, double *surfaceColor)
       double s1[3], s2[3], s3[3];
       double c1[3], c2[3];
 
+      // for grid cell viz:
+      // using <= if test can leave single-pixel gaps between 2 tris
+      // using < if test fixes it
+      // suggested by Nathan Fabian, Nov 2022
+      
       MathExtra::sub3 (zlocal, xlocal, s1);
       MathExtra::sub3 (ylocal, xlocal, s2);
       MathExtra::sub3 (p, xlocal, s3);
       MathExtra::cross3 (s1, s2, c1);
       MathExtra::cross3 (s1, s3, c2);
-      if (MathExtra::dot3 (c1, c2) <= 0) continue;
+      if (MathExtra::dot3 (c1, c2) < 0) continue;
+      //if (MathExtra::dot3 (c1, c2) <= 0) continue;
 
       MathExtra::sub3 (xlocal, ylocal, s1);
       MathExtra::sub3 (zlocal, ylocal, s2);
       MathExtra::sub3 (p, ylocal, s3);
       MathExtra::cross3 (s1, s2, c1);
       MathExtra::cross3 (s1, s3, c2);
-      if (MathExtra::dot3 (c1, c2) <= 0) continue;
+      if (MathExtra::dot3 (c1, c2) < 0) continue;
+      //if (MathExtra::dot3 (c1, c2) <= 0) continue;
 
       MathExtra::sub3 (ylocal, zlocal, s1);
       MathExtra::sub3 (xlocal, zlocal, s2);
       MathExtra::sub3 (p, zlocal, s3);
       MathExtra::cross3 (s1, s2, c1);
       MathExtra::cross3 (s1, s3, c2);
-      if (MathExtra::dot3 (c1, c2) <= 0) continue;
+      if (MathExtra::dot3 (c1, c2) < 0) continue;
+      //if (MathExtra::dot3 (c1, c2) <= 0) continue;
 
       double cNormal[3];
       cNormal[0] = MathExtra::dot3(camRight, normal);
diff --git a/src/image.h b/src/image.h
index 8ab5b17efa..51a0acc61c 100644
--- a/src/image.h
+++ b/src/image.h
@@ -34,6 +34,11 @@ class Image : protected Pointers {
   double *boxcolor;           // color to draw box outline with
   int background[3];          // RGB values of background
 
+  double ambientColor[3];     // light color settings (adjustable by caller)
+  double keyLightColor[3];
+  double fillLightColor[3];
+  double backLightColor[3];
+
   Image(class LAMMPS *, int);
   ~Image() override;
   void buffers();
@@ -80,19 +85,19 @@ class Image : protected Pointers {
   // constant view params
 
   double FOV;
-  double ambientColor[3];
+  //double ambientColor[3];
 
   double keyLightTheta;
   double keyLightPhi;
-  double keyLightColor[3];
+  //double keyLightColor[3];
 
   double fillLightTheta;
   double fillLightPhi;
-  double fillLightColor[3];
+  //double fillLightColor[3];
 
   double backLightTheta;
   double backLightPhi;
-  double backLightColor[3];
+  //double backLightColor[3];
 
   double specularHardness;
   double specularIntensity;