diff --git a/assets/environments/debug/debug.png b/assets/environments/debug/debug.png
index b7ea22b0a6..c8bfb7c934 100644
Binary files a/assets/environments/debug/debug.png and b/assets/environments/debug/debug.png differ
diff --git a/third_party/environments/URL.txt b/third_party/environments/URL.txt
index 05788390f5..99e51129e1 100644
--- a/third_party/environments/URL.txt
+++ b/third_party/environments/URL.txt
@@ -1 +1,2 @@
 https://hdrihaven.com/
+https://mapswire.com/world/physical-maps/
diff --git a/third_party/environments/earth.png b/third_party/environments/earth.png
new file mode 100644
index 0000000000..3bc409da38
Binary files /dev/null and b/third_party/environments/earth.png differ
diff --git a/tools/cmgen/src/CubemapUtils.cpp b/tools/cmgen/src/CubemapUtils.cpp
index 11a4c2b496..650936af99 100644
--- a/tools/cmgen/src/CubemapUtils.cpp
+++ b/tools/cmgen/src/CubemapUtils.cpp
@@ -51,14 +51,14 @@ void CubemapUtils::equirectangularToCubemap(Cubemap& dst, const Image& src) {
             [&](EmptyState&, size_t y, Cubemap::Face f, Cubemap::Texel* data, size_t dim) {
         for (size_t x=0 ; x<dim ; ++x, ++data) {
             // calculate how many samples we need based on dx, dy in the source
-            // x =  cos(phi) sin(theta)
-            // y = -sin(phi)
-            // z = -cos(phi) cos(theta)
+            // x = cos(phi) sin(theta)
+            // y = sin(phi)
+            // z = cos(phi) cos(theta)
             const double3 s0(dst.getDirectionFor(f, x, y));
-            const double t0 = std::atan2(s0.x, -s0.z);
+            const double t0 = std::atan2(s0.x, s0.z);
             const double p0 = std::asin(s0.y);
             const double3 s1(dst.getDirectionFor(f, x+1, y+1));
-            const double t1 = std::atan2(s1.x, -s1.z);
+            const double t1 = std::atan2(s1.x, s1.z);
             const double p1 = std::asin(s1.y);
             const double dt = std::abs(t1 - t0);
             const double dp = std::abs(p1 - p0);
@@ -72,10 +72,10 @@ void CubemapUtils::equirectangularToCubemap(Cubemap& dst, const Image& src) {
                 // Generate numSamples in our destination pixels and map them to input pixels
                 const double2 h = hammersley(uint32_t(sample), iNumSamples);
                 const double3 s(dst.getDirectionFor(f, x + h.x, y + h.y));
-                float xf = float(std::atan2(s.x, -s.z) * M_1_PI);   // range [-1.0, 1.0]
-                float yf = float(std::asin(-s.y) * (2 * M_1_PI));   // range [-1.0, 1.0]
+                float xf = float(std::atan2(s.x, s.z) * M_1_PI);   // range [-1.0, 1.0]
+                float yf = float(std::asin(s.y) * (2 * M_1_PI));   // range [-1.0, 1.0]
                 xf = (xf + 1) * 0.5f * (width -1);           // range [0, width [
-                yf = (yf + 1) * 0.5f * (height-1);           // range [0, height[
+                yf = (1 - yf) * 0.5f * (height-1);           // range [0, height[
                 // we can't use filterAt() here because it reads past the width/height
                 // which is okay for cubmaps but not for square images
                 c += Cubemap::sampleAt(src.getPixelRef((uint32_t)xf, (uint32_t)yf));
diff --git a/tools/cmgen/src/cmgen.cpp b/tools/cmgen/src/cmgen.cpp
index 62fd38f18b..1cb7f2705f 100644
--- a/tools/cmgen/src/cmgen.cpp
+++ b/tools/cmgen/src/cmgen.cpp
@@ -149,8 +149,8 @@ static void printUsage(char* name) {
             "       Extract faces of the cubemap into <dir>\n\n"
             "   --extract-blur=roughness\n"
             "       Blurs the cubemap before saving the faces using the roughness blur\n\n"
-            "   --mirror\n"
-            "       Mirrors generated cubemaps for reflections\n\n"
+            "   --no-mirror\n"
+            "       Skip mirroring of generated cubemaps (for assets with mirroring already backed in)\n\n"
             "   --ibl-samples=numSamples\n"
             "       Number of samples to use for IBL integrations (default 1024)\n\n"
             "\n"
@@ -211,7 +211,7 @@ static int handleCommandLineArgments(int argc, char* argv[]) {
             { "ibl-dfg-multiscatter",       no_argument, nullptr, 'u' },
             { "ibl-samples",          required_argument, nullptr, 'k' },
             { "deploy",               required_argument, nullptr, 'x' },
-            { "mirror",                     no_argument, nullptr, 'm' },
+            { "no-mirror",                  no_argument, nullptr, 'm' },
             { "debug",                      no_argument, nullptr, 'd' },
             { nullptr, 0, 0, 0 }  // termination of the option list
     };
@@ -449,7 +449,6 @@ int main(int argc, char* argv[]) {
             Image temp;
             Cubemap cml = CubemapUtils::create(temp, dim, isHorizontal);
             CubemapUtils::copyImage(temp, inputImage);
-            cml.makeSeamless();
             images.push_back(std::move(temp));
             levels.push_back(std::move(cml));
         } else if (width == 2 * height) {
@@ -461,7 +460,6 @@ int main(int argc, char* argv[]) {
             Image temp;
             Cubemap cml = CubemapUtils::create(temp, dim);
             CubemapUtils::equirectangularToCubemap(cml, inputImage);
-            cml.makeSeamless();
             images.push_back(std::move(temp));
             levels.push_back(std::move(cml));
         } else {
@@ -492,36 +490,33 @@ int main(int argc, char* argv[]) {
             CubemapUtils::generateUVGrid(cml, 1);
         }
 
-        cml.makeSeamless();
         images.push_back(std::move(temp));
         levels.push_back(std::move(cml));
     }
 
-    // Now generate all the mipmap levels
-    generateMipmaps(levels, images);
-
+    // we mirror by default -- the mirror option in fact un-mirrors.
+    g_mirror = !g_mirror;
     if (g_mirror) {
         if (!g_quiet) {
             std::cout << "Mirroring..." << std::endl;
         }
-
-        std::vector<Cubemap> mirrorLevels;
-        std::vector<Image> mirrorImages;
-
-        for (auto& level : levels) {
-            Image temp;
-            Cubemap cml = CubemapUtils::create(temp, level.getDimensions());
-            CubemapUtils::mirrorCubemap(cml, level);
-            cml.makeSeamless();
-
-            mirrorImages.push_back(std::move(temp));
-            mirrorLevels.push_back(std::move(cml));
+        Image temp;
+        Cubemap cml = CubemapUtils::create(temp, levels[0].getDimensions());
+        CubemapUtils::mirrorCubemap(cml, levels[0]);
+        std::swap(levels[0], cml);
+        std::swap(images[0], temp);
+    } else {
+        if (!g_quiet) {
+            std::cout << "Skipped mirroring." << std::endl;
         }
-
-        std::swap(levels, mirrorLevels);
-        std::swap(images, mirrorImages);
     }
 
+    // make the cubemap seamless
+    levels[0].makeSeamless();
+
+    // Now generate all the mipmap levels
+    generateMipmaps(levels, images);
+
     if (g_sh_compute) {
         if (!g_quiet) {
             std::cout << "Spherical harmonics..." << std::endl;