How to create a perfectly symmetrical flat onion dome?

This shape specifically, it’s called an onion dome. I can’t make it perfectly symmetrical using the curve tool.

Answers:

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Method 1

Using the following method, you can edit the shape, or tweak the curves, and it will be automatically reflected on the other side.

1. Using a guide, draw one half of the shape with the Pen Tool.
2. Open the Appearance panel
3. Add a Transform Effect with the following settings:

Edit the curves, and the shape will be automatically reflected.

Method 2

Starting with an uppercase S (Helvetica light) > Rotate it -30º

• Select the S
• Menu Type > Create Outlines
• Get the Reflect Tool and holding Alt click on the bottom curve right edge > Reflect Vertical > Copy
• Add an ellipse at the top center of the inside area (green on the image)
• Select all
• Using the Shape Builder Tool and holding Alt to delete, click on each stroke under the ellipse

• Using the Shape Builder Tool, click the inside area to create a new shape (yellow on the image)
• Delete the rest of the letters S

• Fill the new shape with the same color
• Rotate 180º
• Pathfinder > Unite if necessary

Method 3

Here’s how I’d do it…. no guess work….

• Draw an oval
• Use Object > Path > Add Anchor Points to add additional anchor points to the oval. — Added anchors are always positioned exactly midway between existing anchors.
• Use the Direct Selection Tool to move the top anchor upward
• Use the Convert Anchor Point Tool to move the Bezier handles of the top anchor down, Hold the Shift key down to ensure the handles are 90° vertical from their anchor. And move them both so the handle is in the same position under the anchor.
• Finally use the Free Transform Tool to possibly make the overall shape taller (or shorter).

This animation is using AICS6, but it’s the same steps in AICC.

Method 4

Try to use pen tool instead of the curve tool.
Draw the half side of the shape.
Copy the shape, and flip it and join the lines to complete the shape.

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0