VisIt Gaussian Mode
The Volume Plot's Gaussian control allows you a wide range of precise controls over the shape of the opacity transfer function curve. The Gaussian control has four different control points that allow you to change the shape of the curve. These are the height, shape, position, and width control points. The height control point controls the height of the curve along the Y-axis. The shape control point controls the shape of the curve. As you can see below, there are many possible shapes that can be made. The position control point controls the position of the curve along the X-axis. The width control point controls the width of the curve. Additional Gaussian curves can be added to the transfer function just by clicking in the black area.