Multi-Monitor Distortion Workaround Shader

[Matthias1231 39]

I've been experimenting with a workaround for the lack of multi-view for multi-monitor setups and reducing the distortion on the side screens.
I figured I could write a ReShade shader that squeezes the outside screens while leaving the center one unchanged.

I haven't had time to really test this much yet, but I wanted to share my efforts so far and see if that is of any benefit to any other multi-monitor simmers.

This requires Reshade installed for MSFS. Just save the shader code to a file called MultiMonitor.fx and copy it to your ReShade shader folder for MSFS and enable it in the Reshade menu. 
It only works with 3 monitors of the same size and resolution. You can either run in surround mode or drag the MSFS window to cover all 3 screens.

Yes, I know, some of the screen space is wasted, you can't click on anything in the outside views, performance impact, blah blah blah. 

The math still needs work but you can squeeze the side view with the Factor value and distort it with the Power value.

When I have more time I will revisit the math and also add bezel correction.

3 monitor setup distortion

Shader squeezing outside views with default settings

ReShade shader Code:

#include "ReShadeUI.fxh"

uniform float factor < __UNIFORM_SLIDER_FLOAT1
	ui_min = 0.0; ui_max = 5;
	ui_tooltip = "Factor";
> = 1;

uniform float power < __UNIFORM_SLIDER_FLOAT1
	ui_min = 1; ui_max = 10;
ui_tooltip = "Power";
> = 2.5;

#include "ReShade.fxh"

float3 MultiMonitorPass(float4 vpos : SV_Position, float2 texcoord : TexCoord) : SV_Target
{
	float3 color;
	float2 sourceCoord;

	float texTimes3 = texcoord.x * 3.0;
	float monitorPos = texTimes3 - 1.0;
	float monitorIx = floor(monitorPos);

	float texTimes3Centered = texTimes3 - 1.5;
	float absTex3 = abs(texTimes3Centered) - 0.5;
	if (absTex3 > 0 && absTex3 < 1) absTex3 = pow(absTex3, power);
	float centerOffs = absTex3 * monitorIx;
	float finalOffs = centerOffs * factor;
	float sourceX = texcoord.x + finalOffs;

	sourceCoord.x = sourceX;
	sourceCoord.y = texcoord.y;

	color = (sourceX < 0 || sourceX > 1) ? 0 : tex2D(ReShade::BackBuffer, sourceCoord).rgb;
	return color;
}

technique MultiMonitor
{
	pass
	{
		VertexShader = PostProcessVS;
		PixelShader = MultiMonitorPass;
	}
}

 

[MarkDH 234]

2 hours ago, Matthias1231 said:

I've been experimenting with a workaround for the lack of multi-view for multi-monitor setups and reducing the distortion on the side screens.
I figured I could write a ReShade shader that squeezes the outside screens while leaving the center one unchanged.

I haven't had time to really test this much yet, but I wanted to share my efforts so far and see if that is of any benefit to any other multi-monitor simmers.

This requires Reshade installed for MSFS. Just save the shader code to a file called MultiMonitor.fx and copy it to your ReShade shader folder for MSFS and enable it in the Reshade menu. 
It only works with 3 monitors of the same size and resolution. You can either run in surround mode or drag the MSFS window to cover all 3 screens.

Yes, I know, some of the screen space is wasted, you can't click on anything in the outside views, performance impact, blah blah blah. 

The math still needs work but you can squeeze the side view with the Factor value and distort it with the Power value.

When I have more time I will revisit the math and also add bezel correction.

3 monitor setup distortion

 

I applaud the effort but surely this just gives the same result as using a narrower window and adjusting the zoom to achieve the same vertical FoV? To me this would only make sense if you ran a custom screen resolution at a wider-than-actual screen width and your tweak squashed it down to the actual screen width.

Edited September 16, 2020 by MarkDH

[Matthias1231 39]

It's not the same as an FOV change. The default projection using three monitors is based on the monitors being aligned on a flat surface. This shader results in a partial (fake) projection adjustment compensating for the angle at which the outside screens are turned towards the user.

[MarkDH 234]

19 minutes ago, Matthias1231 said:

It's not the same as an FOV change. The default projection using three monitors is based on the monitors being aligned on a flat surface. This shader results in a partial (fake) projection adjustment compensating for the angle at which the outside screens are turned towards the user.

I maintain (at least on first glance) that you will get the same effect by running a narrower window and adjusting the zoom. The required zoom setting will be larger (longer effective focal length) and hence the distortion away from the centre of the image will be less extreme. I have yet to install MSFS but by all accounts it seems to behave pretty much exactly like FSX and P3D.

[Matthias1231 39]

You keep maintaining then. Thanks for participating.