hoosiertransfer-mod/desktopRuntime/resources/assets/eagler/glsl/deferred/skybox_atmosphere.fsh

129 lines
4.0 KiB
GLSL

#line 2
/*
* Copyright (c) 2023 lax1dude. All Rights Reserved.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
* WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
*/
precision lowp int;
precision highp float;
precision mediump sampler2D;
in vec2 v_position2f;
layout(location = 0) out vec4 output4f;
uniform sampler2D u_skyNormals;
uniform vec4 u_sunDirectionIntensity4f;
uniform vec3 u_scatteringCoefficient3f;
uniform float u_altitude1f;
uniform vec4 u_blendColor4f;
// Source: https://github.com/wwwtyro/glsl-atmosphere
#define PI 3.141592
#define iSteps 16
#define jSteps 4
vec2 rsi(vec3 r0, vec3 rd, float sr) {
float a = dot(rd, rd);
float b = 2.0 * dot(rd, r0);
float c = dot(r0, r0) - (sr * sr);
float d = (b*b) - 4.0*a*c;
if (d < 0.0) return vec2(1e5,-1e5);
a *= 2.0;
d = sqrt(d);
return vec2(-b - d, -b + d) / a;
}
vec3 atmosphere(vec3 r, vec3 r0, vec3 pSun, float iSun, float rPlanet, float rAtmos, vec3 kRlh, float kMie, float shRlh, float shMie, float g) {
pSun = normalize(pSun);
r = normalize(r);
vec2 p = rsi(r0, r, rAtmos);
if (p.x > p.y) return vec3(0.0);
p.y = min(p.y, rsi(r0, r, rPlanet).x);
float iStepSize = (p.y - p.x) / float(iSteps);
float iTime = 0.0;
vec3 totalRlh = vec3(0.0);
vec3 totalMie = vec3(0.0);
float iOdRlh = 0.0;
float iOdMie = 0.0;
float mu = dot(r, pSun);
float mumu = mu * mu;
float gg = g * g;
float pRlh = 3.0 / (16.0 * PI) * (1.0 + mumu);
float pMie = 3.0 / (8.0 * PI) * ((1.0 - gg) * (mumu + 1.0)) / (pow(1.0 + gg - 2.0 * mu * g, 1.5) * (2.0 + gg));
for (int i = 0; i < iSteps; i++) {
vec3 iPos = r0 + r * (iTime + iStepSize * 0.5);
float iHeight = length(iPos) - rPlanet;
float odStepRlh = exp(-iHeight / shRlh) * iStepSize;
float odStepMie = exp(-iHeight / shMie) * iStepSize;
iOdRlh += odStepRlh;
iOdMie += odStepMie;
float jStepSize = rsi(iPos, pSun, rAtmos).y / float(jSteps);
float jTime = 0.0;
float jOdRlh = 0.0;
float jOdMie = 0.0;
for (int j = 0; j < jSteps; j++) {
vec3 jPos = iPos + pSun * (jTime + jStepSize * 0.5);
float jHeight = length(jPos) - rPlanet;
jOdRlh += exp(-jHeight / shRlh) * jStepSize;
jOdMie += exp(-jHeight / shMie) * jStepSize;
jTime += jStepSize;
}
vec3 attn = exp(-(kMie * (iOdMie + jOdMie) + kRlh * (iOdRlh + jOdRlh)));
totalRlh += odStepRlh * attn;
totalMie += odStepMie * attn;
iTime += iStepSize;
}
return iSun * (pRlh * kRlh * totalRlh + pMie * kMie * totalMie);
}
void main() {
if(u_blendColor4f.a >= 1.0) {
output4f = vec4(u_blendColor4f.rgb, 0.0);
return;
}
vec4 normalIn = textureLod(u_skyNormals, v_position2f, 0.0);
if(normalIn.a != 1.0) {
output4f = vec4(0.0);
return;
}
normalIn.xyz *= 2.0;
normalIn.xyz -= 1.0;
output4f = vec4(atmosphere(
normalIn.xyz, // normalized ray direction
vec3(0,6373e3 + u_altitude1f * 50.0,0), // ray origin
u_sunDirectionIntensity4f.xyz, // position of the sun
u_sunDirectionIntensity4f.w, // intensity of the sun
6371e3, // radius of the planet in meters
6471e3, // radius of the atmosphere in meters
vec3(5.5e-6, 13.0e-6, 22.4e-6), // Rayleigh scattering coefficient
21e-6, // Mie scattering coefficient
8e3, // Rayleigh scale height
1.2e3, // Mie scale height
0.758 // Mie preferred scattering direction
), 0.0);
if(u_blendColor4f.a > 0.0) {
output4f.rgb = mix(output4f.rgb, u_blendColor4f.rgb, u_blendColor4f.a);
}
}