Rendering menu > Effects > Environment and Effects dialog > Effects panel > Add > Add Effect dialog > Lens Effects > Choose any effect, and click the (>) arrow button. > Parameters tab of the rollout for that effect > Falloff Curve (under the Circular or Section Color group)
The Circular Falloff graph allows you to add weight to a particular color applied to your Lens Effect. By weighting the colors that you apply you can choose to display more of one color than another. You can also make the transition of colors gradual from one color to the next or you can create a sharp edge to the transition.
The Circular Falloff graph has controls at the top for creating and moving points on a curve on the graph below. The curve represents the range of colors you have selected in the Circular Color group box to apply to the current Lens Effect. When you open the graph you will notice that there is already a line with a point on each end which represents the linear transition from one color to the next. By placing points along the curve, you can drag these points to increase or decrease a colors intensity or to eliminate it altogether.
Buttons are available at the bottom of the graph that allow you to change the display of the graph. You can also manually enter a horizontal or vertical position by entering a value into the two entry boxes.
Move—Moves selected points in any direction. Click and hold the Move button to display the flyout where you can select a button to move in any direction, move only in the horizontal direction, or move only in the vertical direction. The Move function remains active until you click another button. The button is yellow while it is active.
Scale Point—Scales a point vertically. Click once to enable Scale Point. The Scale Point function remains active until you click another button. The button is yellow while it is active.
Add Point—Allows you to add points anywhere along the Circular Falloff curve. Click and hold the Add Point button to display the flyout from which you can choose a button to add either a Corner Point or a Bezier-Smooth Point. Click once to enable Add Point. The Add Point function remains active until you click another button. The button is yellow while it is active.
Delete Point—Deletes selected points.
Horizontal Position—Allows you to manually enter a horizontal position value for a selected point.
Vertical Position—Allows you to manually enter a vertical position value for a selected point.
Pan—Allows you to click and drag the Circular Falloff graph window to move it left and right or up and down. Click once to enable panning. Pan remains active until you click another button. The button is yellow while it is active.
Zoom Extents—Fits the curve within the graph window both vertically and horizontally so that the entire curve is visible.
Zoom Horizontal Extents—Fits the curve horizontally within the graph window so that the full length of the curve is visible.
Zoom Vertical Extents—Fits the curve vertically within the Circular Falloff graph window so that the full height of the curve is visible.
Zoom Horizontally—Scales the width of the Circular Falloff graph window.
Zoom Vertically—Scales the length of the Circular Falloff graph window.
Zoom—Zooms in and out of the entire Circular Falloff graph window.
Zoom Region—Allows you to drag a region in the Circular Falloff graph window and scale that region to fill the window.