Question Simple Fade Effect Doesn't Work For Very Small Values

I'm trying to make a simple function in a compute shader which fades the trail left behind by moving agents by simply subtracting a small amount each pass. The current code is as follows:

RWTexture2D<float4> Result;

float fadeSpeed;

float deltaTime;



[numthreads(8, 8, 1)]

void TrailFade (uint3 id: SV_DispatchThreadID)

{

    float4 original = Result[id.xy];

    float4 newVal = max(0, original - fadeSpeed * deltaTime);



    Result[id.xy] = newVal;

}

Using an example fadeSpeed of 0.1, the code works perfectly fine. However, I wanted to experiment with longer trails, so I decreased the value to 0.01 and the trails don't dissapate at all. Doing some further poking around, it seems like the value needs to be >= 0.099 or else it won't work. In fact, 0.99 works properly, but 0.98 does not.

Because of that issue, I have to assume it's some weird rounding / precision error, but I believe the float should be more than precise enough. Apologies if this is some obvious problem, I'm very new to Compute Shaders and this kind of low-level programming in general.

 

Sorry, I found the answer! The Texture I was using simply wasn't big enough to store the precision I wanted it to. I solved it by using RenderTextureFormat.ARGBFloat