Blending displays seamlessly with the Edge Blending module [⭐ Pro]

⭐ This article revolves around a Pro feature.

In "Configuring an advanced projection setup with multiple displays", you've learned how to arrange the Output Setup in HeavyM in order to send areas of the Canvas to different display destinations.

In the use case we presented (two 1920x1080 projectors), the setup could end there if both projectors are meant to project on completely different spaces or side by side but with a gap between them. If you intend to use multiple projectors in order to expand your projection area, you'll need to use the Edge Blending module in addition.

What's the use of Edge Blending?

In reality, it's virtually impossible to combine precisely two projection areas side by side and make them seem like a single huge one seamlessly just with warping adjustments and no overlap or gap.

That's why, instead of trying to place the projection areas side by side, it's better to actually voluntarily make them overlap a bit and then apply some blending transformations to correct the appearance of the overlap strip.

These corrections are necessary, otherwise the overlap will be very visible, as you can see below:

Using the Edge Blending module

Let's use our previous case of two 1920x1080 projectors for this. Here, we want to set up both horizontally to create a wide projection area.

Before we start to configure HeavyM, remember that for a successful edge blending, the first thing you’ll need to do is to make sure that your projectors are perfectly aligned physically, one to the other. Of course, we'll see that you can correct small misalignments with HeavyM. But if your projectors are not aligned properly by hand, your edge blending will not be seamless.

Let's move on to HeavyM now. Since multiprojection has already been covered in another article, we'll go over the basic steps rapidly.

1. Choose the Setup Output mode with or Output → Setup....
2. In a simple multiprojection case, our canvas size would be (1920+1920)x1080. But since we're going to make our areas overlap horizontally, we're gonna "lose" some pixels on the width.
   Let's say our overlap is on 400px this time, that makes our canvas size 3440x1080.
   
3. Add a second screen and snap it to the right side of the test card, so that the canvas is fully covered and the screens overlap by 400px.
   
4. Launch the fullscreen projection for each screen by selecting it and assigning it a Destination output.
   
5. Now, you should see something like this on your projection surface (I mean the real life projection this time):
   
   Note: at this step, if your projectors are not exactly placed side by side with the perfect overlap and you see on the test card that both areas don't fit perfectly, you should use the Warping options in HeavyM to correct the geometry of the outputs until you reach a matching rectangular shape.
   
   Assuming your outputs now create a perfect 3440x1080 rectangular projection area, there's one last thing to correct: the appearance of the overlap strip. To do so, first select each screen in the Output Setup and "Enable" their Soft Edge parameter one by one in the Edge Blending section.
   
6. It already should look better! As you can see, HeavyM has detected that the screens overlap on one side and has already applied a correction automatically.
   Now, it might not be perfect right away so it's up to you to adjust the Blend Curve and Gamma Correction settings, until you can see the overlap strip and reach two perfectly blended projection areas.
   
7. You're all set! Just remember to untick "Show test card" (top right corner) to reveal your canvas and click on "Ok" to save you setup and exit the setup window.