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Quick Start

If you want to get started quickly, just start clicking in the canvas area on the right, and then click the Refine and Degrade buttons a few times. You'll see those the straight lines you created turn into curves in no time!


Basic Operation

Adding Control Points Left-Click on the canvas area on the right. Points will appear where you click. Lines will appear between the points as you go. To insert points between two existing points, Left-Click on the line that connects them, and drag the new point to where you want it.
Moving Control Points Drag the desired point with the left mouse button to the desired location. If you drag an endpoint on top of the other endpoint, the two points will become one point, and the system of points will become a loop.
Removing Control Points and Lines Right-Click on the point or line you wish to remove. A line can only be removed when the system of points form a loop.
Moving Control Tangents If the tangents in the control polygon are drawn (see Render Options), you may drag the tangent arrow/line from either end with the left mouse button to change its orientation. If you want to reset the tangent to its default, right-click either end of the arrow/line.
Refining & Degrading The Refine button will increase the refinement level of the curve, making it smoother. The applet will not allow more than 9 levels of refinement. The Degrade button will decrease the refinement level of the curve, making it less smooth.
Progress Bar The progress bar at the bottom of the controls is activated whenever the applet is calculating the curve. When dragging the mouse, the curve is constantly calculated and re-calculated, and at low refinement levels, the progress bar may flicker.


Basic Options

Primary Algorithm The first drop-down box allows you to select the subdivision algorithm to use.
Secondary Algorithm After the primary algorithm as been applied for 0-9 iterations, you may select a second subdivision algorithm to use for later iterations.
Mid-Tangent Placement Using the slider, you may specify the placement of the midtangents as a percentage of the angle between the edge and the tangent. Using the text box next to the slider, you can specify percentages less than 0 or greater than 100. You may also specify the number of iterations for this midtangent placement to be used. Later iterations will use 50%. (These options are used only with the Tangent-Driven subdivision algorithm.)
Directional Tangents Allows you to toggle whether the tangents in the control polygon are directional or non-directional. (Used only with the Tangent-Driven subdivision algorithm.)
Load Pre-Made Allows you to select premade control polygons from a list. Any changes you've made to the control polygon will be discarded.


Advanced Options

All of these options apply to the Tangent-Driven subdivision algorithm only.

Control Point Tangents Allows you to select the algorithm to use for calculating default tangents at points in the control polygon.
Subdivision Point Tangents Allows you to select the algorithm to use for calculating the tangents at the subdivision points.
No Popping Edges This option will enable or disable the variation of the Tangent-Driven algorithm that prevents discontinuous movement of the curve as two adjacent edges are moved past one another. The threshold allows you to configure the largest angle between two edges that the No-Popping-Edges variation will be applied.
No Popping Tangents This option enables or disables the variation of the Tangent-Driven algorithm that prevent discontinuous movement of the curve as the user drags the tangent around to change its orientation. The threshold specifies the largest angle at which the No-Popping-Tangents variation will be applied.
Resist Coincident Points This option allows you to enable and configure the Resist-Coincident-Points variation of the Tangent-Driven algorithm.


Render Options

Points Turns on/off the drawing of points in the control polygon or in the subdivided curve.
Edges Turns on/off the drawing of edges in the control polygon or in the subdivided curve.
Tangents Turns on/off the drawing of tangents in the control polygon or in the subdivided curve.
Mid-Tangents Turns on/off the drawing of midtangents in the control polygon or in the subdivided curve.
Point Color Configures the color of points drawn in the control polygon or in the subdivided curve.
Edge Color Configures the color of edges drawn in the control polygon or in the subdivided curve.
Tangent Color Configures the color of tangents drawn in the control polygon or in the subdivided curve.
Mid-Tangent Color Configures the color of midtangents drawn in the control polygon or in the subdivided curve.
Background Color Configures the color of the background.


FAQ

The applet won't load. What can I do?

First make sure that your browser has java enabled. If it is, and it still doesn't work, try updating your java. You can download JRE 5.0 update 5 here. If it's still not working, try closing the browser and opening it again. (I've seen this work with Firefox on Linux. I'm not sure why it happens.)

Another reason could be that you are accessing the web through a proxy, and the proxy will not allow Java applets to load. See your system administrator to address this issue.