isnan in shader seems not working properly!

Questions & Answers
1

I need to check NaN values in the fragment shader, but it seems that the HLSL intrinsic function isnan is not working properly.

here is the part of the shader:

float ori;
float4 frag(v2f I) : SV_Target
{
    float4 c = {0,0,0,0};
    if (isnan(ori))
    {
        return c;
    }

    c = {1,1,1,1};
    return c;
}

I get white color when ori is set to 0, but when I set ori to NaN, instead of full transparent, showing the background color, it always shows black color.

so , my question is that is the isnan not supported in shaderlab, or I need to open some shader compiler flags, or else how to check this NaN value without the isnan function.

I am testing the shader in unity 2019.3.0b8
Thanks.

2

float IsNan_float(float In)
{
return (In < 0.0 || In > 0.0 || In == 0.0) ? 0 : 1;
}

I tried custom function and it works.