Passing Custom Float1 from VS to PixelShader

I’m trying to pass a Float1 (singe float value) from Vertex Shader to Pixel Shader. Looks like in HLSL I have to define a valid “semantic” for this to work.

So I chose SV_CLIPDISTANCE, but apparently this semantic is hard-wired to discard all pixels where this goes negative. So I can’t use it to pass a negative value to the Pixel Shader.

What semantic should I use for a “user custom” value? I can’t find a location in the Urho3D code which defines the available Custom/User semantics (ones not used for other purposes already).

Here is my HLSL Code:

void VS(float4 iPos : POSITION,
float2 iTexCoord : TEXCOORD0,
out float2 oTexCoord : TEXCOORD0,
out float oCustomValue : SV_CLIPDISTANCE0,
out float4 oPos : OUTPOSITION)

and

void PS(
float2 oTexCoord : TEXCOORD0,
float iCustomValue : SV_CLIPDISTANCE0,
out float4 oColor : OUTCOLOR0)

Whenever my “oCustomValue” goes negative, the pixel disappears (guessing because SV_CLIPDISTANCE0 is hardwired to behave this way).

SV literally means “System Value”, i.e. “value used by GPU itself”.
Just used TEXCOORD1, or whatever index is free

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Thanks! I didn’t realize I could use TEXCOORD1 as a Float1. I figured it was only allowed to be used for Float2. Using TEXCOORD1 fixed the issue entirely.