diff --git a/Terrain2/Shaders/TerrainAlgorithms.metal b/Terrain2/Shaders/TerrainAlgorithms.metal
index 04c2b93..1d91d2e 100644
--- a/Terrain2/Shaders/TerrainAlgorithms.metal
+++ b/Terrain2/Shaders/TerrainAlgorithms.metal
@@ -82,29 +82,30 @@ kernel void updateGeometryVertexNormals(constant packed_float3 *meshPositions [[
                                         device packed_float3 *vertexNormals [[buffer(GeneratorBufferIndexNormals)]],
                                         uint2 tid [[thread_position_in_grid]])
 {
-    float3 normal = float3();
+    const uint2 segs = uniforms.terrainSegments;
 
+    float3 normal = float3();
     uint adjacent = 0;
 
     if (tid.y > 0 && tid.x > 0) {
-        uint aIndex = 2 * segmentIndex(uint2(tid.x - 1, tid.y - 1), uniforms.terrainSegments) + 1;
+        uint aIndex = 2 * segmentIndex(uint2(tid.x - 1, tid.y - 1), segs) + 1;
         normal += faceNormals[aIndex];
         adjacent += 1;
     }
-    if (tid.y > 0 && tid.x < (uniforms.terrainSegments.x - 1)) {
-        uint segment = segmentIndex(uint2(tid.x, tid.y - 1), uniforms.terrainSegments);
+    if (tid.y > 0 && tid.x < segs.x) {
+        uint segment = segmentIndex(uint2(tid.x, tid.y - 1), segs);
         uint bIndex = 2 * segment;
         uint cIndex = 2 * segment + 1;
         normal += faceNormals[bIndex] + faceNormals[cIndex];
         adjacent += 2;
     }
-    if (tid.x < (uniforms.terrainSegments.x - 1) && tid.y < (uniforms.terrainSegments.y - 1)) {
-        uint dIndex = 2 * segmentIndex(tid, uniforms.terrainSegments);
+    if (tid.x < segs.x && tid.y < segs.y) {
+        uint dIndex = 2 * segmentIndex(tid, segs);
         normal += faceNormals[dIndex];
         adjacent += 1;
     }
-    if (tid.x > 0 && tid.y < (uniforms.terrainSegments.y - 1)) {
-        uint segment = segmentIndex(uint2(tid.x - 1, tid.y), uniforms.terrainSegments);
+    if (tid.x > 0 && tid.y < segs.y) {
+        uint segment = segmentIndex(uint2(tid.x - 1, tid.y), segs);
         uint eIndex = 2 * segment + 1;
         uint fIndex = 2 * segment;
         normal += faceNormals[eIndex] + faceNormals[fIndex];
@@ -113,8 +114,8 @@ kernel void updateGeometryVertexNormals(constant packed_float3 *meshPositions [[
 
     if (adjacent != 0) {
         normal = normalize(normal / float(adjacent));
-        uint vertexNormalIndex = segmentIndex(tid, uniforms.terrainSegments);
-        vertexNormals[vertexNormalIndex] = normal;
+        uint idx = segmentIndex(tid, segs);
+        vertexNormals[idx] = normal;
     }
 }
 
diff --git a/Terrain2/Terrain.swift b/Terrain2/Terrain.swift
index 5f6c26b..a0b146d 100644
--- a/Terrain2/Terrain.swift
+++ b/Terrain2/Terrain.swift
@@ -201,7 +201,7 @@ class Terrain: NSObject {
             let normalsBuffer = mesh.vertexBuffers[BufferIndex.normals.rawValue]
             computeEncoder.setBuffer(normalsBuffer.buffer, offset: normalsBuffer.offset, index: GeneratorBufferIndex.normals.rawValue)
             computeEncoder.setBuffer(uniforms.buffer, offset: uniforms.offset, index: GeneratorBufferIndex.uniforms.rawValue)
-            computeEncoder.dispatchThreads(MTLSize(width: 2 * Int(segments.x * segments.y), height: 1, depth: 1), threadsPerThreadgroup: MTLSize(width: 8, height: 8, depth: 1))
+            computeEncoder.dispatchThreads(MTLSize(width: Int(segments.x + 1), height: Int(segments.y + 1), depth: 1), threadsPerThreadgroup: MTLSize(width: 8, height: 8, depth: 1))
             computeEncoder.popDebugGroup()
             computeEncoder.endEncoding()
         }