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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


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 '14 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 '14 at 12:46
up vote 56 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 '14 at 18:34
You may want to add that you should start in object mode. – Thomas Ross Nov 9 '14 at 22:26
What if I want to deform one corner of the cube with a curve, instead of just cutting it? – Fabián Mar 5 '15 at 4:58
Doesn't seem to work every time. After I've turned a cube into a triangular shape it refuses to cut it for some reason. – mattboy May 16 '15 at 14:42
I couldn't make this work with an imported .svg curve, is this normal? – fabrice d Mar 31 at 8:09

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 '14 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 '14 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 '14 at 18:33

In addition to learning Blender's native boolean operations, I highly recommend you check out a free Addon called BoolTool (version 0.2) Here is the link to the addon.

Here are my notes for using the BoolTool addon. It makes booleans so easy that you can use Blender like ShadowBox in ZBrush.

Q. How do I use the BoolTool Add-On?

A. Create a cube. Duplicate the cube (Shift+D). Drag the duplicated cube (Brush object) so that it intersects with the original cube (Canvas object). Shift+RMB click to add the original cube (Canvas object) to the duplicate cube's (Brush object's) selection. In the BoolTool Tab in the ToolShelf, under Brush, click either Union, Intersection or Difference (or click on each one to see what they do). You will now see the Brush object perform according to the selected operation under the Brush Menu. Making a Brush object works great as a mask to cut in or add detail. The Canvas properties will affect the Canvas object. With the Canvas object selected you can also use the Brush properties which will obviously affect the Brush object. You can modify the Brush object in the 3D View such as scaling it or duplicating it to make multiple brushes. By selecting the Canvas object you can also manipulate a selected brush object in the Brush properties such as hiding it, applying it or removing it.

If you don't want to make a Brush, you can simply select what would ordinarily be the Brush object and then add the Canvas object to the selection and then just press the operation under Direct and a boolean operation will be performed. The results of the boolean operation will be stored in the active selection (the last selected object) and you can have multiple objects that act as Brush objects.

Here are the hotkeys as found in the Object menu:
Brush Union = Ctrl+Numpad Plus
Brush Difference = Ctrl+Numpad Minus
Brush Intersection = Ctrl+Numpad Asterix
Direct Union = Ctrl+Shift+Numpad Plus
Direct Difference = Ctrl+Shift+Numpad Minus
Direct Intersection = Ctrl+Shift+Numpad Asterix

Note: BoolTool will automatically convert Curve objects to mesh objects when you apply it as a Brush or Direct Boolean operation.

To use the Draw Poly Brush, switch to the view that you want to work such as Front view and then click on Draw Poly Brush. You will have a grease pencil that you can use to draw lines. Simply click where you want each point to be. You don't need to close the poly. The two open endpoints will automatically be closed. When finished drawing, press Enter and the polygon will be created. Poly Brush size will scale the depth of the polygon. You can use the Poly Brush as a Brush or Directly.

Inside the BoolTool AddOns Preferences, you can check Fast Transformations (marked experimental and disabled by default). Fast Transformations replaces the G/R/S hotkeys for a new custom version that handles Boolean operations faster. The Blender viewport can struggle with high poly models when trying to carve out parts of the canvas. With this enabled, there will be a new option in the Brush properties that says Fast Vis, which when used, will allow the visibility to be changed on the fly. Use it if your workflow is being bogged down. Note: with Fast Vis on, it will be enabled for all the brushes.

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protected by iKlsR Apr 4 '15 at 6:03

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