Question

float4 color = tex2D(inputSampler, TexCoord);
     //compute distance from center
float distance = color.a>0.3f?length(TexCoord - 0.5f):1.0f;

What is color.a&gt and why is there a ; in the middle of that second line?

Answer 1

Response to the original question: “Can someone tell me what this snippet of HLSL code means?

float4 color = tex2D(inputSampler, TexCoord);
  //compute distance from center 
float distance = color.a>0.3f?length(TexCoord - 0.5f):1.0f;

what is color.a&gt and why is there a ; in the middle of that second line?”

---

Its a html escape sequence screwup. > should be > (“greater than” symbol).

So it should be:

float4 color = tex2D(inputSampler, TexCoord);
     //compute distance from center
float distance = color.a > 0.3f?length(TexCoord - 0.5f):1.0f;

Likewise if you encounter < it is probably < (“less than” symbol). Other common ones ones are:

• " -> ‘"‘
• & -> ‘&‘
•   -> ‘ ‘ (space)

What the pixel shader is actually doing is if the alpha of the sampled texture at this point is greater than 0.3, distance is the length from the sampled texcoord (U,V) location to (0.5, 0.5) i.e. the center of the texture sampled from. If the alpha is 0.3 or less, then distance is set to 1.0f.

The distance value is obviously used later in the shader to apply some pixel effect.