Hi guys

Is the texture coordinate format for SampleLevel the same as the viewport (ie +-1.0 x and y) or is it integer based?

The reason I ask is I need to do a edge check in my pixel shader where I will sample 4 pixels around each point to see if they are black. Not sure how to go about this.

Also, anyone got a efficient solution for a white noise generator in HLSL? I found this: http://www.reedbeta.com/blog/2013/01/12/quick-and-easy-gpu-random-numbers-in-d3d11/

but from the comments I understand it can be rather slow.

Also found this in the comments:

return fract(sin(dot(n.xy, vec2(12.9898, 78.233)))* 43758.5453);

But would like to know if there is anything faster out there. I want to noise up the texture for a certain distance within the edges as I locate them.

Thanks

JB

As far as white noise goes, I'm playing around with this shader at the moment.

layout(location = 0) uniform float time;
out vec4 frag_color;

uint hash(uint x)
{
    x = ((x >> 16) ^ x) * 0x85ebca6b;
    x = ((x >> 13) ^ x) * 0xc2b2ae35;
    x = ((x >> 16) ^ x);
    return x;
}
 
uint hash(uvec2 v) { return hash(v.x ^ hash(v.y)); }
uint hash(uvec3 v) { return hash(v.x ^ hash(v.y) ^ hash(v.z)); }
uint hash(uvec4 v) { return hash(v.x ^ hash(v.y) ^ hash(v.z) ^ hash(v.w)); }

float floatConstruct(uint m)
{
    m &= 0x007FFFFFu;
    m |= 0x3F800000u;

    float  f = uintBitsToFloat(m);
    return f - 1.0;
}

float random(float x) { return floatConstruct(hash(floatBitsToUint(x))); }
float random(vec2 v) { return floatConstruct(hash(floatBitsToUint(v))); }
float random(vec3 v) { return floatConstruct(hash(floatBitsToUint(v))); }
float random(vec4 v) { return floatConstruct(hash(floatBitsToUint(v))); }

void main()
{
    frag_color = vec4(random(vec3(gl_FragCoord.xy, time)).xxx, 1.0);
}

It costs 0.28ms @ 1080p on my GTX 760, which is not all that much slower than the fract/sin implementation. The results however are a lot better. The fract/sin implementation produces a lot of noticeable patterns for me, and because of the way trig functions are implemented differently on various GPUs, it can have a lot of variability. This is GLSL by the way, but I'm sure you can modify it if you want to try it.

awesome stuff. thanks a bunch.