diff --git a/src/consts.cu b/src/consts.cu
index 2252c36..72733f6 100644
--- a/src/consts.cu
+++ b/src/consts.cu
@@ -49,6 +49,6 @@ void copyConstantsToDevice() {
 
 // ----------------------- TransferFunction -----------------------
 __device__ float d_opacityK;
-__device__ float d_sigmoidOne;
-__device__ float d_sigmoidTwo;
+__device__ float d_sigmoidShift;
+__device__ float d_sigmoidExp;
 __device__ int d_tfComboSelected;
diff --git a/src/consts.h b/src/consts.h
index 0811c7f..239d58e 100644
--- a/src/consts.h
+++ b/src/consts.h
@@ -65,8 +65,8 @@ struct ColorStop {
 // factor for the opacity function
 extern __device__ float d_opacityK;
 // sigmoid function variables
-extern __device__ float d_sigmoidOne;
-extern __device__ float d_sigmoidTwo;
+extern __device__ float d_sigmoidShift;
+extern __device__ float d_sigmoidExp;
 // combo box index
 extern __device__ int d_tfComboSelected;
 
diff --git a/src/gui/input/Widget.cpp b/src/gui/input/Widget.cpp
index 92001ef..b6ba24c 100644
--- a/src/gui/input/Widget.cpp
+++ b/src/gui/input/Widget.cpp
@@ -27,8 +27,8 @@ Widget::Widget(GLFWwindow* window) {
   this->renderOnce = false;
 
   this->opacityK = 0;
-  this->sigmoidOne = 0.5f;
-  this->sigmoidTwo = -250.0f;
+  this->sigmoidShift = 0.5f;
+  this->sigmoidExp = -250.0f;
   this->tfComboSelected = 0;
 };
 
@@ -50,8 +50,8 @@ void Widget::tick(double fps) {
 
   ImGui::Begin("Transfer Function Controls");
   ImGui::DragInt("k (log [1e-10, 1])", &this->opacityK, 1, 0, 100, "%d%%", ImGuiSliderFlags_AlwaysClamp);
-  ImGui::DragFloat("sigmoidOne", &this->sigmoidOne, 0.01f, 0.0f, 1.0f, "%.2f");
-  ImGui::InputFloat("sigmoidTwo", &this->sigmoidTwo, 10.0f, 100.0f, "%.0f");
+  ImGui::DragFloat("sigmoidShift", &this->sigmoidShift, 0.01f, 0.0f, 1.0f, "%.2f");
+  ImGui::InputFloat("sigmoidExp", &this->sigmoidExp, 10.0f, 100.0f, "%.0f");
   
   // the items[] contains the entries for the combobox. The selected index is stored as an int on this->tfComboSelected
   // the default entry is set in the constructor, so if you want that to be a specific entry just change it
@@ -115,8 +115,8 @@ void Widget::copyToDevice() {
   this->opacityKReal = std::pow(10.0f, (-10 + 0.1 * this->opacityK));
   cudaMemcpyToSymbol(&d_opacityK, &this->opacityKReal, sizeof(float));
 
-  cudaMemcpyToSymbol(&d_sigmoidOne, &this->sigmoidOne, sizeof(float));
-  cudaMemcpyToSymbol(&d_sigmoidTwo, &this->sigmoidTwo, sizeof(float));
+  cudaMemcpyToSymbol(&d_sigmoidShift, &this->sigmoidShift, sizeof(float));
+  cudaMemcpyToSymbol(&d_sigmoidExp, &this->sigmoidExp, sizeof(float));
   cudaMemcpyToSymbol(&d_tfComboSelected, &this->tfComboSelected, sizeof(float));
 }
 
diff --git a/src/gui/input/Widget.h b/src/gui/input/Widget.h
index 15370c7..52727b3 100644
--- a/src/gui/input/Widget.h
+++ b/src/gui/input/Widget.h
@@ -21,8 +21,8 @@ public:
   int tfComboSelected;
   int opacityK;
   float opacityKReal;
-  float sigmoidOne;
-  float sigmoidTwo;
+  float sigmoidShift;
+  float sigmoidExp;
 
   ImGuiIO io;
 
diff --git a/src/illumination/transferFunction.cu b/src/illumination/transferFunction.cu
index 57525af..6930284 100644
--- a/src/illumination/transferFunction.cu
+++ b/src/illumination/transferFunction.cu
@@ -7,12 +7,12 @@
 
 __device__ float opacityFromGradient(const Vec3 &grad) {
     float gradMag = grad.length();
-    float alpha = 1.0f - expf(-d_opacityK * gradMag);  // TODO: This parameter probably has the wrong scale
+    float alpha = 1.0f - expf(-1 * gradMag);  // TODO: This parameter probably has the wrong scale
     return alpha;
 }
 
 __device__ float opacitySigmoid(float val) {
-    return 1.0f / (1.0f + expf(d_sigmoidTwo * (val - d_sigmoidOne)));
+    return 1.0f / (1.0f + expf(d_sigmoidExp * (val - d_sigmoidShift)));
 }
 
 __device__ Color3 colorMap(float normalizedValues, const ColorStop stops[], int N) {
diff --git a/src/linalg/mat.cu b/src/linalg/mat.cu
index 745ddfb..788867d 100644
--- a/src/linalg/mat.cu
+++ b/src/linalg/mat.cu
@@ -62,6 +62,7 @@ __device__ Vec3 computeGradient(float* volumeData, const int volW, const int vol
     float hy = DLON;  // y => width => lon
     float hz = DLEV;  // z => depth => alt
     
+    // Default
     float dfdx = (sampleVolumeTrilinear(volumeData, volW, volH, volD, fx + hx, fy, fz) -
                   sampleVolumeTrilinear(volumeData, volW, volH, volD, fx - hx, fy, fz)) / (2.0f * hx);
 
@@ -71,6 +72,14 @@ __device__ Vec3 computeGradient(float* volumeData, const int volW, const int vol
     float dfdz = (sampleVolumeTrilinear(volumeData, volW, volH, volD, fx, fy, fz + hz) -
                   sampleVolumeTrilinear(volumeData, volW, volH, volD, fx, fy, fz - hz)) / (2.0f * hz);
 
+    // // DEBUG (TODO: Delete) - Back to nearest
+    // float dfdx = (sampleVolumeNearest(volumeData, volW, volH, volD, (int)roundf(fx + 1), (int)roundf(fy), (int)roundf(fz)) -
+    //               sampleVolumeNearest(volumeData, volW, volH, volD, (int)roundf(fx - 1), (int)roundf(fy), (int)roundf(fz))) / (2.0f * hx);
+    // float dfdy = (sampleVolumeNearest(volumeData, volW, volH, volD, (int)roundf(fx), (int)roundf(fy + 1), (int)roundf(fz)) -
+    //               sampleVolumeNearest(volumeData, volW, volH, volD, (int)roundf(fx), (int)roundf(fy - 1), (int)roundf(fz))) / (2.0f * hy);
+    // float dfdz = (sampleVolumeNearest(volumeData, volW, volH, volD, (int)roundf(fx), (int)roundf(fy), (int)roundf(fz + 1))  -
+    //               sampleVolumeNearest(volumeData, volW, volH, volD, (int)roundf(fx), (int)roundf(fy), (int)roundf(fz - 1))) / (2.0f * hz);
+
     return Vec3::init(dfdx, dfdy, dfdz);
 };