Here are my settings in the sidebysiderift.fx file in the fx folder in your Virieo folder. These settings are good for a Zeiss VR One but you can easily edit some numbers for your hmd:
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sampler2D TexMap0;
sampler2D TexMap1;
float2 Warp(float2 Tex : TEXCOORD0)
{
float2 newPos = Tex;
float c = -81.0f/15.0f;
float u = Tex.x*2.0f - 1.0f;
float v = Tex.y*2.0f - 1.0f;
newPos.x = c*u/(pow(v, 2) + c);
newPos.y = c*v/(pow(u, 2) + c);
newPos.x = (newPos.x + 1.0f)*0.5f;
newPos.y = (newPos.y + 1.0f)*0.5f;
return newPos;
}
float4 SBSRift(float2 Tex : TEXCOORD0) : COLOR
{
float4 tColor;
float2 newPos = Tex;
float2 warpedTexCoord;
// This is all pretty lazy, I haven't generalised for a variable vertical percentage so it's fixed at 80%.
//float screenRatio = 1.6f // 16:10 screen, use 1.777777777f for 16:9 screen
//float visibleRatio = 1f; // 16:10 screen, use 0.9f for 16:9 screen. These numbers would need to change
// for a different vertical %. I've left all those calculations out
// These numbers are constants for the screen size and a given vertical usage, so rather than calculating them for every pixel
// I'm just putting the number directly into xRangeToUse. Normally this would be done outside the shader
// and passed in.
float xRangeToUse = 0.625f; //visibleRatio / screenRatio;
float xHalfOfRangeNottoUse = 0.1875f; // (1f - xRangeToUse) * 0.5f;
newPos.y = newPos.y * 1.25f - 0.125f; // 80% of vertical.
if(newPos.x < 0.5)
{
newPos.x = (newPos.x * 2.0f * xRangeToUse) + xHalfOfRangeNottoUse;
warpedTexCoord = Warp(newPos);
tColor = tex2D(TexMap0, warpedTexCoord);
}
else
{
newPos.x = (((newPos.x - 0.5f) * 2.0f)* xRangeToUse) + xHalfOfRangeNottoUse;
warpedTexCoord = Warp(newPos);
tColor = tex2D(TexMap1, warpedTexCoord);
}
// remove everything between here and the next comment except "return tColor;" if you want the clamped texture around the edge instead of black
if ((warpedTexCoord.y > 1.0f) || (warpedTexCoord.y < 0.0f)) {
return 0;
}
else {
return tColor;
}
// This is the next comment
}
technique ViewShader
{
pass P0
{
VertexShader = null;
PixelShader = compile ps_2_0 SBSRift();
}
}
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Near the top of that code you see the line "float c = -81.0f/15.0f;" If you change that "15" it will change the amount of distortion for the image.
Soon after that are the lines
newPos.x = c*u/(pow(v, 2) + c);
newPos.y = c*v/(pow(u, 2) + c);
You can add a multiplier after the last "c" to increase or reduce the overall image size.
For example:
newPos.x = c*u/(pow(v, 2) + c*2.0);
newPos.y = c*v/(pow(u, 2) + c*2.0);
This will double the image size filling up your screen but cutting out a significant amount of the image.
If you want to make the image smaller, you could do something like this:
newPos.x = c*u/(pow(v, 2) + c*0.75);
newPos.y = c*v/(pow(u, 2) + c*0.75);
I hope all of this information helps someone get their own iphone rift going! Good luck!
