I'm using blender for editing desktop recordings using open broadcaster software.

I would like to highlight areas of the screen to draw attention to them by surrounding them with a red rectangular box.

How can I do this in blender? Do I need to create a transparent image containing a rectangle of the correct size for each area using another application like Inkscape, or is there a better way?


Making the shape in a 2 paint program like GIMP or drawing program like Illustrator is quickest. But with Blender you can animate and iterate more quickly. You can use a mask from the UV image editor.

  1. First press F12 to render the present frame into the Image editor.
  2. then change to Mask Mode and create a new mask (name it)

Create a mask

  1. In the VSE add the mask as a strip in the place that you want it to appear

add mask strip

  1. Select the new mask strip and add a Gaussian Blur, set blur in properties panel (N key) to 10 or more (depending on render resolution).

set blur in properties

  1. With Blur effect selected add a curve modifier and make a sharp peak.

make the blur an outline

  1. Now add a color correction modifier. Set the Gain value to a nice bright color.

make a pretty color

  1. Change the mask strip's Blend type (in the properties panel again) to add.

Now you should see a colourful box outline around your region of interest.

pretty green outline... ta da!

What is cool about this approach is that you can animate the shape, color and thickness of the curve during the edit.

  • $\begingroup$ Or you know you could just make a shape in a 3d scene with Freestyle lines. $\endgroup$
    – 3pointedit
    Jul 31 '16 at 12:55
  • $\begingroup$ after pressing F12 to render the current frame in the image editor, how do I draw the rectangular box you have in you first screenshot? I can't see any tools for creating that object. $\endgroup$
    – Chris Snow
    Jul 31 '16 at 20:04

In the end I performed the following steps:

  • In Blender
    • Press F12 to open the current frame into the Image editor
    • Select Menu: Mask -> Save as Image [1]
    • Edit the saved image using Inkscape, add a rectangle without fill
  • In Inkscape select menu: Export Bitmap
    • Export Area: Drawing
    • Click Export, replacing Orignal
  • In Blender
    • Open VSE
    • In strip editor, select menu: Add -> Image and open the edited image

[1] I would have used Image -> Edit externally but hit the error Image path '.' not found even though my external editor was set to /usr/bin/inkscape in my preferences.

  • $\begingroup$ Great solution. And in a drawing application you get to add text and arrows etc much easier than in Blender. $\endgroup$
    – 3pointedit
    Jul 31 '16 at 23:26

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