GoogleCodeExporter
commented
9 years ago So I'm not sure it's ANGLE or if it's DirectX. I haven't go through the entire
shaders but...
using the WEBGL_debug_shaders extension shows the shader passed to the driver.
The function in question looks the same on both GLSL and HLSL
--GLSL--
vec3 webgl_411896f5d9a657de(in vec3 webgl_f4a871322329f1f){
return ((((8.0 * pow(3.1415927, 3.0)) * pow((pow(1.0003, 2.0) - 1.0), 2.0)) *
6.105) / ((76349999198241540557242368.0 * pow(webgl_f4a871322329f1f, vec3(4.0,
4.0, 4.0))) * 5.7550001));
}
--HLSL--
float3 _webgl_411896f5d9a657de(in float3 _webgl_f4a871322329f1f)
{
{
return ((((8.0 * pow(3.1415927, 3.0)) * pow((pow(1.0003, 2.0) - 1.0), 2.0)) *
6.105) / ((76349999198241541000000000.0 * pow(_webgl_f4a871322329f1f,
float3(4.0, 4.0, 4.0))) * 5.7550001));
;
}
}
;
The calling points too
--GLSL--
vec3 webgl_6ecdfd37473d07b4 = (webgl_411896f5d9a657de(vec3(6.8000003e-07,
5.4999998e-07, 4.4999999e-07)) * webgl_6a82dfb3c4d3d759);
--HLSL--
float3 _webgl_6ecdfd37473d07b4 =
(_webgl_411896f5d9a657de(float3(6.8000003e-007, 5.4999998e-007,
4.4999999e-007)) * _webgl_6a82dfb3c4d3d759);
I though maybe HLSL's compiler doesn't have enough resolution for the tiny
values? As in maybe it's using floats to compute compile time constants instead
of doubles? So, I tried converting that function to C++
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
const float pi = 3.141592653589793238462643383279502884197169f;
const float n = 1.0003f; // refractive index of air",
const float N = 2.545E25f; // number of molecules per unit volume for air at",
// 288.15K and 1013mb (sea level -45 celsius)",
const float pn = 0.035f; // depolatization factor for standard air",
float totalRayleigh(float lambda) {
return (8.0f * powf(pi, 3.0f) * powf(powf(n, 2.0f) - 1.0f, 2.0f) * (6.0f + 3.0f * pn)) /
(3.0f * N * powf(lambda, 4.0f) * (6.0f - 7.0f * pn));
}
int main() {
//const vec3 lambda = vec3(680E-9, 550E-9, 450E-9);
printf("%g, %g, %g", totalRayleigh(680E-9), totalRayleigh(550E-9), totalRayleigh(450E-9));
return EXIT_SUCCESS;
}
which prints
5.80703e-06, 1.35687e-05, 3.02789e-05
Plugging those into totalRayleigh still produces the correct result so that
wasn't the issue.
OTOH changing totalRayleigh to just return vec3(0,0,0) produces the incorrect
blue result. Not sure if that's helpful or notOriginal comment by g...@chromium.org on 14 Dec 2014 at 11:45
Original issue reported on code.google.com by
g...@chromium.orgon 14 Dec 2014 at 11:11