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Coming from SketchUp one of the tools I miss most is the circle draw tool which lets you draw a circle on any face and then you could extrude it in/out. The only tool that I know of that comes close to this is the knife tool but this would be very impractical to cut out with the knife

Example:

enter image description here

Is there any tool in blender that can match this function? also how could you do this with squares?

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do you want the circle to be a seperate mesh? –  Vader Mar 21 at 12:45
    
No I want it as part of the cubes face so that if you extrude it in it would leave a hole –  Qwertie Mar 21 at 12:46

3 Answers 3

up vote 18 down vote accepted

Knife Project Tool

The tool you are looking for is the Knife Project tool. Here's how to use it:

  1. Create your cube that you want to put the circle on
  2. Add a circle curve: SHIFTA -> Curve -> Circle
  3. Position the circle in front of the face you want to put the circle on, as shown here (highlighted in green):

    enter image description here

  4. Now go to the viewport where the circle visually appears where you want your circle to be on your cube, like this:

    enter image description here

  5. Now select the circle, then hold down SHIFT and select the cube.

  6. Switch into Edit mode
  7. Tools panel (T) -> Mesh Tools section -> Add section -> click Knife Project (Note: In 2.70, the Mesh Tools section is located in the Tools tab)

    This will result in the cube now having a circular hole in the front face:

    enter image description here

  8. If you now want to fill the hole with a face, select all the vertices of the hole and press F.

NOTE: In this example, the circle is considered the Knife, which is kind of like a cookie cutter, or perhaps even a bullet, and so when you click on the Knife Project button, what Blender does is it projects/shoots the knife (here the circle) from the visual angle in your active viewport. So, make sure you have the knife visually lined up so that when it projects/shoots onto your destination object, it will make the circle right where you want it. Here are two examples of projecting from different angles:

enter image description here

An interesting note is that in the example above where the knife is visually at an angle, the resulting face on the destination object is NOT automatically deleted (see the highlighted face on the lower example.)

Also, you can indeed use any shape as a knife:

enter image description here

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Lovely. This knife projection saved me. I wanted to cut the f hole design of a violin into the body of it. This project was a saviour. Thanks –  Rexford Oct 29 at 18:34
    
You may want to add that you should start in object mode. –  Th0masR0ss Nov 9 at 22:26

enter image description here

enter image description here

enter image description here

Maybe you can do like this, But I don't know if this is what you want.

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Looks close to what I was looking for but this generates lots of extra geometry. –  Qwertie Mar 21 at 12:43
    
You can subdivdes only one surface,But will produce more than or less 4 verts –  人生无望何以为继 Mar 21 at 13:14

There is not super simple way of doing this like there is in Sketchup. There are a few ways to do this in blender but this is the best way I have found.

Here is how:

  1. Select the face and subdivide it to add more geometry for the circle

    enter image description here

  2. Select the edges that will make up the circle

    enter image description here

  3. Scale the edges to sphere, Alt Shift S

    • scale all the way to 1 to make it perfectly circular.

    enter image description here


The method described above will work nicely on faces that are square, but if the face is a rectangle the circle will look stretched.

enter image description here

To fix this:

  1. Open up the user preferences, Ctrl Alt U

  2. In the addons tab search for "Looptools" and install it.

    enter image description here

  3. Close the user preferences

  4. Select the edges of the circle

  5. Run the Space command from the loop tools addon, W -> Loop Tools -> Space

    enter image description here

    • You will notice that it looks a bit better

    enter image description here

  6. To make it look circular run the scale to sphere command again, Alt Shift S

    enter image description here

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I think this way also is cool. However the Knife projection happens to fit in many scenarios and saves time too. Thanks for this approach too. –  Rexford Oct 29 at 18:33

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