How would you cut a shape out of an object using another object?

Question

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:

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

Answer 1

Knife Project Tool

Edit: Since 2.9, the Knife Project tool works this way:

• Select the object you want to edit, switcht to Edit mode.
• Ctrl left click to select the cutter object.
• Go in the header menu > Mesh panel > Knife Project.

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):

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

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:

9. 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:

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:

Answer 2

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

Answer 3

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

   

2. Select the edges that will make up the circle

   

3. Scale the edges to sphere, Alt Shift S

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

   

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

To fix this:

1. Open up the user preferences, Ctrl Alt U

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

   

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

   

   • You will notice that it looks a bit better

   

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

   

Answer 4

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

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

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

A:

1. Create a cube.
2. Duplicate the cube (Shift+D).
3. Drag the duplicated cube (Brush object) so that it intersects with the original cube (Canvas object).
4. Shift+Right-click click to add the original cube (Canvas object) to the duplicate cube's (Brush object's) selection.
5. 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 Asterisk
Direct Union = Ctrl+Shift+Numpad Plus
Direct Difference = Ctrl+Shift+Numpad Minus
Direct Intersection = Ctrl+Shift+Numpad Asterisk

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:

1. 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.
2. 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.
3. 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 add-on's 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.

Answer 5

If your cutting mesh is part of the same object, select it in Edit mode then header menu > Face > Intersect, choose Knife or Boolean depending on the result you want (Knife will cut the shape on the roof, Boolean will merge or subtract the shape, depending on the option you choose in the Operator box):