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