Mastering Bezier curves: Cubic Bezier curves

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ClipStudioOfficial

ClipStudioOfficial

This tool is useful when you want to draw a smoother curve than a freehand curve.

Bezier curves are made using control points (and direction points) that define the shape of the curve.


https://tips.clip-studio.com/en-us/articles/1029


[1] What is a cubic Bezier curve?

Cubic Bezier curves consist of multiple control points and direction points.


If you draw it on a vector layer, you can adjust the control points and direction points after drawing the line. However, you cannot adjust the control points or direction points if the line is drawn on a raster layer.

Go to the [Tool] palette > [Figure] tool and choose the [Continuous curve] sub tool.

In the [Tool Property] palette, choose the [Cubic Bezier] icon in the [Curve] option.


Note: In the initial settings, the specification method of the sub tool [Continuous curve] is set to [By drag].

However, if it is set to [By click], the tool will behave in the same way as the quadratic Bezier curve, and you will not be able to use it as in this lesson.


Hint:

The curve preview has changed since Clip Studio Paint Ver.1.5.5. You can see the line color and width while drawing.

To revert the simplified view like in previous versions, go to the [File] menu > [Preferences] dialog box > [Tool] and turn on [Use simple display for lines being created with the figure tools].


[2] How to use the cubic Bezier tool

1. Setting the control points and direction points


For cubic Bezier curves, you can specify the control points in the following ways.


■ Click to specify control points

When you specify control points by clicking, they will be connected with straight lines.


■ Drag to specify control points

When you specify control points by dragging, the start point becomes the control point, and the end point of the drag becomes the direction point that determines the direction and size of the curve.



2. Tool basics


■ Straight line/Angled line

Click to specify control points and connect them with straight lines. Click the final control point ④ and press the [Enter] key to confirm.


■ Simple curve

Drag the control point to set the direction point.

Lines that extend from the control point ① will curve according to the direction and length of the direction point.

After selecting the control point ②, confirm the line by pressing the [Enter] key.


■ Different curves at the start and end points

Drag the control points of the start and end points to set the direction points. These allow you to set a curve for each control point.

In this example, drag the control point ② downwards to set the direction point, and press [Enter] to confirm the line art.

Notice that when you drag the control point of ② down, the direction point is set symmetrically on the opposite side.


■ Curve with a corner

① Create a curve with a corner in the following steps: Drag the control point ① to set the direction point, click the next control point ②, and drag the following control point ③ to set the direction point.

Press [Enter] after setting the control point ③ and draw the line art.


[3] Adjusting direction points

If you are drawing on a vector layer, you can adjust the control points and direction points afterwards to reshape the lines.

Select the line art using the [Object] sub tool of the [Operation] tool to readjust the control point and direction point.


■ Adjusting curves

Direction points extend to the left and right of the control points between the curves.

If you adjust the position of one direction point, the opposite direction point will move in point symmetry.

Direction points represent the vertex of the curve.


■ Adjusting straight lines

Move the control point at the end of the straight line to adjust the length and direction of the straight line.


Let’s try drawing a perfect circle

Display the grid, and use the large square as a guild line.

Note: How to show grid: [View] menu > [ Grid ]


Set the direction points as shown in the figure from the middle of the side of the square.


In the same way, set the direction point of the other sides in order. Please refer to the following figure and try to set the position of the direction point to create a line art.


At the end, click the starting point to close the line.


If you want to make a perfect circle, the distance of the two direction points that extend from a control point should be equivalent.


[4] Switching corners

You can switch the corners of a control point afterwards. Switch corners to individually control the left and right direction points extending from the control point.

Click and select the control point at the top of the circle with the [Operation] > [Object] sub tool.


Display the right-click menu while the control point is selected in red, and select [Switch corners].


Creating a heart shape from a perfect circle

Let’s transform the perfect circle into a heart shape using switch corners.


Move the control point at the top of the circle down.


Drag the two direction points to make a V-like shape. The two direction points should be line-symmetric.


Then, move the control point at the bottom.


Switch corners, adjust the direction point, and reshape the bottom part (tail of the heart shape).


[5] Tracing the illustration drawn in freehand

Detailed adjustments of the curve is possible for Cubic Bezier curves. You can trace the illustration drawn by freehand and then clean the curves.


① Draw a rough sketch on the raster layer freely.


② Create a vector layer above to trace, and draw the lines using the [Continuous curve] tool according to the rough sketches.

Continuous curves on the vector layers can be readjusted at any time, so the lines do not have to be perfect.


③ After confirming the line art, select the line art using the [Object] sub tool of the [Operation] tool.


④ Use the two different points (the red control point and the blue direction points) to adjust the line art.

Drag the direction point to adjust the curve or drag the control point to move the line itself.


⑤ Delete excess control points

Select an unnecessary control point, display the menu and select [Delete control point].

Adjust other control points or direction points to clean the line art.


⑥ After reshaping the line art, select it and adjust the [Main color] or [Brush Size (Width of line)] on the [Tool Property] palette.


Bezier curves are very useful for drawing pop illustration that require smooth lines.

Use various tools depending on the taste of the illustration.


Hint:

You cannot undo Bezier curve operations.

Press the [Delete]/[BackSpace] key or right click while operating the Bezier curve to go back one by one.

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