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[HOWTO] Easy Non-Square Webcam

Making a non-square webcam is easy with OBS 0.11+ (it may work on earlier versions, I haven't tested). The way we will do this is to create an alpha mask with an alpha channel.

Alpha Masks are on the opposite side of the idea coin from a Chroma Key. While not exactly "opposites", they care about the opposite thing. A Chroma Key cares about the a single color (or range of colors) and makes them transparent. An Alpha Mask takes a single color (or location) and makes it visible.

In the alpha mask image below, the thing we want visible is the green piece, but we are only using it as a shape, not a color. Do not focus on the fact that it is green, focus on the fact it is a hexagon. It could simply be ANY PNG file that has transparency.

An Alpha Mask will make the NON-Transparent pixels (in this case, the hexagon) VISIBLE when applied to a different image. Think of it as subtracting the image down to the shape of the mask.

The alpha channel option makes your alpha mask based on the transparent pixels in the source image. The alpha color option makes your alpha mask based on a specific color you select (much like the Chroma Key, but remember, the "opposite", meaning the color you choose will the VISIBLE portion of the image).

Here is the Alpha Mask you will need for a Heroes of the Storm hexagon. Using this shape, you can put your webcam in the spot where the hero portrait is in game:

Download and save this file to a stream assets directory (if you don't have one, make one, you will be using a lot of assets for a great stream).

  1. Under Sources click the ➕ icon
  2. Select Video Capture Device
  3. Leave the Create New selected
  4. Rename as appropriate
  5. Click [OK]
  6. Select your device
  7. Use the 320x240 preset
  8. Click [OK]
  9. Right-Click the new device
  10. Select Filters
  11. Under Effect Filters, click the ➕ icon
  12. Add an Image Mask/Blend filter.
  13. Click [OK]
  14. Set the type as Alpha Mask (Alpha Channel)
  15. Browse to the mask file you saved.
  16. Click [Close]

For More Information
To learn more about Alpha (both Alpha Color and Alpha Mask)
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Awesome, wuwuw
Thank you, easy to configure and clear explanations ! I could just add for those who don't find it obvious : to create your filter, generate a .png of the same dimensions as dimensions you choose for your webcam, then, color in it to get the form you want.
Nice!Really good for people who don't like to put a green screen over their webcam to crop out using Chroma Key(like me)