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HDR: Use precomputed uniforms for atmospheric scattering

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This commit is contained in:
Fernando García Liñán 2021-08-19 12:50:01 +02:00
parent d4dfafaac7
commit 94f4007793
4 changed files with 41 additions and 47 deletions
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32
Shaders/HDR/atmos-aerial-perspective.frag
View file

@ -16,14 +16,16 @@ out vec4 fragColor;
in vec2 texCoord;
uniform mat4 fg_ViewMatrixInverse;
uniform vec3 fg_CameraPositionCart;
uniform vec3 fg_CameraPositionGeod;
uniform vec3 fg_SunDirectionWorld;
uniform sampler2D transmittance_lut;
uniform sampler2D multiscattering_lut;
uniform mat4 fg_ViewMatrixInverse;
uniform vec3 fg_CameraPositionCart;
uniform vec3 fg_SunDirectionWorld;
uniform float fg_SunZenithCosTheta;
uniform float fg_CameraDistanceToEarthCenter;
uniform float fg_EarthRadius;
const float PI = 3.141592653;
const float ATMOSPHERE_RADIUS = 6471e3;
const float TOTAL_SLICES = 32.0;
@ -43,11 +45,7 @@ vec3 getValueFromLUT(sampler2D lut, float sunCosTheta, float normalizedHeight);
void main()
{
vec3 up = normalize(fg_CameraPositionCart);
float sunCosTheta = dot(fg_SunDirectionWorld, up);
// Account for the depth layer we are currently in
// FIXME: We should probably be writing the pixel center
float x = texCoord.x * TOTAL_SLICES;
vec2 coord = vec2(fract(x), texCoord.y);
// Depth goes from the 0 to DEPTH_RANGE in a squared distribution.
@ -59,16 +57,16 @@ void main()
vec3 fragPos = positionFromDepth(coord, 1.0);
vec3 rayDir = vec4(fg_ViewMatrixInverse * vec4(normalize(fragPos), 0.0)).xyz;
float cameraHeight = length(fg_CameraPositionCart);
float earthRadius = cameraHeight - max(fg_CameraPositionGeod.z, 0.0);
vec3 rayOrigin = fg_CameraPositionCart;
// Handle the camera being underground
float earthRadius = min(fg_EarthRadius, fg_CameraDistanceToEarthCenter);
float atmosDist = raySphereIntersection(rayOrigin, rayDir, ATMOSPHERE_RADIUS);
float groundDist = raySphereIntersection(rayOrigin, rayDir, earthRadius);
float tmax;
if (cameraHeight < ATMOSPHERE_RADIUS) {
if (fg_CameraDistanceToEarthCenter < ATMOSPHERE_RADIUS) {
// We are inside the atmosphere
if (groundDist < 0.0) {
// No ground collision, use the distance to the outer atmosphere
@ -99,8 +97,8 @@ void main()
t = newT;
vec3 samplePos = rayOrigin + rayDir * t;
float height = length(samplePos) - earthRadius;
float normalizedHeight = height / (ATMOSPHERE_RADIUS - earthRadius);
float height = length(samplePos) - fg_EarthRadius;
float normalizedHeight = height / (ATMOSPHERE_RADIUS - fg_EarthRadius);
float mieScattering, mieAbsorption;
vec3 rayleighScattering, ozoneAbsorption;
@ -110,9 +108,9 @@ void main()
vec3 sampleTransmittance = exp(-dt*extinction);
vec3 sunTransmittance = getValueFromLUT(
transmittance_lut, sunCosTheta, normalizedHeight);
transmittance_lut, fg_SunZenithCosTheta, normalizedHeight);
vec3 multiscattering = getValueFromLUT(
multiscattering_lut, sunCosTheta, normalizedHeight);
multiscattering_lut, fg_SunZenithCosTheta, normalizedHeight);
vec3 S =
rayleighScattering * (rayleighPhase * sunTransmittance + multiscattering) +

18
Shaders/HDR/atmos-multiple-scattering.frag
View file

@ -9,11 +9,10 @@ out vec3 fragColor;
in vec2 texCoord;
uniform vec3 fg_CameraPositionCart;
uniform vec3 fg_CameraPositionGeod;
uniform sampler2D transmittance_lut;
uniform float fg_EarthRadius;
const float PI = 3.141592653;
const float ATMOSPHERE_RADIUS = 6471e3;
const int SQRT_SAMPLES = 4;
@ -44,8 +43,7 @@ void main()
float sunCosTheta = texCoord.x * 2.0 - 1.0;
vec3 sunDir = vec3(-sqrt(1.0 - sunCosTheta*sunCosTheta), 0.0, sunCosTheta);
float earthRadius = length(fg_CameraPositionCart) - fg_CameraPositionGeod.z;
float altitude = mix(earthRadius, ATMOSPHERE_RADIUS, texCoord.y);
float altitude = mix(fg_EarthRadius, ATMOSPHERE_RADIUS, texCoord.y);
vec3 rayOrigin = vec3(0.0, 0.0, altitude);
vec3 Ltotal = vec3(0.0);
@ -58,7 +56,7 @@ void main()
vec3 rayDir = generateRayDir(theta, phi);
float atmosDist = raySphereIntersection(rayOrigin, rayDir, ATMOSPHERE_RADIUS);
float groundDist = raySphereIntersection(rayOrigin, rayDir, earthRadius);
float groundDist = raySphereIntersection(rayOrigin, rayDir, fg_EarthRadius);
float tmax;
if (groundDist < 0.0) {
@ -84,8 +82,8 @@ void main()
t = newT;
vec3 samplePos = rayOrigin + rayDir * t;
float height = length(samplePos) - earthRadius;
float normalizedHeight = height / (ATMOSPHERE_RADIUS - earthRadius);
float height = length(samplePos) - fg_EarthRadius;
float normalizedHeight = height / (ATMOSPHERE_RADIUS - fg_EarthRadius);
float mieScattering, mieAbsorption;
vec3 rayleighScattering, ozoneAbsorption;
@ -116,8 +114,8 @@ void main()
float pHeight = length(p);
vec3 up = p / pHeight;
float normHeight = (pHeight - earthRadius)
/ (ATMOSPHERE_RADIUS - earthRadius);
float normHeight = (pHeight - fg_EarthRadius)
/ (ATMOSPHERE_RADIUS - fg_EarthRadius);
float sunZenithCosTheta = dot(sunDir, up);
vec3 transmittanceFromGround = getValueFromLUT(

30
Shaders/HDR/atmos-sky-view.frag
View file

@ -13,13 +13,13 @@ out vec3 fragColor;
in vec2 texCoord;
uniform vec3 fg_CameraPositionCart;
uniform vec3 fg_CameraPositionGeod;
uniform vec3 fg_SunDirectionWorld;
uniform sampler2D transmittance_lut;
uniform sampler2D multiscattering_lut;
uniform float fg_SunZenithCosTheta;
uniform float fg_CameraDistanceToEarthCenter;
uniform float fg_EarthRadius;
const float PI = 3.141592653;
const float ATMOSPHERE_RADIUS = 6471e3;
@ -37,9 +37,9 @@ void main()
{
// Always leave the sun right in the middle of the texture as the skydome
// model is already being rotated.
vec3 up = normalize(fg_CameraPositionCart);
float sunCosTheta = dot(fg_SunDirectionWorld, up);
vec3 sunDir = vec3(-sqrt(1.0 - sunCosTheta*sunCosTheta), 0.0, sunCosTheta);
vec3 sunDir = vec3(-sqrt(1.0 - fg_SunZenithCosTheta*fg_SunZenithCosTheta),
0.0,
fg_SunZenithCosTheta);
float azimuth = 2.0 * PI * texCoord.x; // [0, 2pi]
// Apply a non-linear transformation to the elevation to dedicate more
@ -48,16 +48,16 @@ void main()
float elev = l*l * sign(l) * PI * 0.5; // [-pi/2, pi/2]
vec3 rayDir = vec3(cos(elev) * cos(azimuth), cos(elev) * sin(azimuth), sin(elev));
float cameraHeight = length(fg_CameraPositionCart);
float earthRadius = cameraHeight - max(fg_CameraPositionGeod.z, 0.0);
vec3 rayOrigin = vec3(0.0, 0.0, fg_CameraDistanceToEarthCenter);
vec3 rayOrigin = vec3(0.0, 0.0, cameraHeight);
// Handle the camera being underground
float earthRadius = min(fg_EarthRadius, fg_CameraDistanceToEarthCenter);
float atmosDist = raySphereIntersection(rayOrigin, rayDir, ATMOSPHERE_RADIUS);
float groundDist = raySphereIntersection(rayOrigin, rayDir, earthRadius);
float tmax;
if (cameraHeight < ATMOSPHERE_RADIUS) {
if (fg_CameraDistanceToEarthCenter < ATMOSPHERE_RADIUS) {
// We are inside the atmosphere
if (groundDist < 0.0) {
// No ground collision, use the distance to the outer atmosphere
@ -86,8 +86,8 @@ void main()
t = newT;
vec3 samplePos = rayOrigin + rayDir * t;
float height = length(samplePos) - earthRadius;
float normalizedHeight = height / (ATMOSPHERE_RADIUS - earthRadius);
float height = length(samplePos) - fg_EarthRadius;
float normalizedHeight = height / (ATMOSPHERE_RADIUS - fg_EarthRadius);
float mieScattering, mieAbsorption;
vec3 rayleighScattering, ozoneAbsorption;
@ -97,9 +97,9 @@ void main()
vec3 sampleTransmittance = exp(-dt*extinction);
vec3 sunTransmittance = getValueFromLUT(
transmittance_lut, sunCosTheta, normalizedHeight);
transmittance_lut, fg_SunZenithCosTheta, normalizedHeight);
vec3 multiscattering = getValueFromLUT(
multiscattering_lut, sunCosTheta, normalizedHeight);
multiscattering_lut, fg_SunZenithCosTheta, normalizedHeight);
vec3 S =
rayleighScattering * (rayleighPhase * sunTransmittance + multiscattering) +

8
Shaders/HDR/atmos-transmittance.frag
View file

@ -11,8 +11,7 @@ out vec3 fragColor;
in vec2 texCoord;
uniform vec3 fg_CameraPositionCart;
uniform vec3 fg_CameraPositionGeod;
uniform float fg_EarthRadius;
const float ATMOSPHERE_RADIUS = 6471e3;
const int TRANSMITTANCE_STEPS = 40;
@ -27,8 +26,7 @@ void main()
float sunCosTheta = texCoord.x * 2.0 - 1.0;
vec3 sunDir = vec3(-sqrt(1.0 - sunCosTheta*sunCosTheta), 0.0, sunCosTheta);
float earthRadius = length(fg_CameraPositionCart) - fg_CameraPositionGeod.z;
float altitude = mix(earthRadius, ATMOSPHERE_RADIUS, texCoord.y);
float altitude = mix(fg_EarthRadius, ATMOSPHERE_RADIUS, texCoord.y);
vec3 rayOrigin = vec3(0.0, 0.0, altitude);
float dist = raySphereIntersection(rayOrigin, sunDir, ATMOSPHERE_RADIUS);
@ -41,7 +39,7 @@ void main()
t = newT;
vec3 samplePos = rayOrigin + sunDir * t;
float height = length(samplePos) - earthRadius;
float height = length(samplePos) - fg_EarthRadius;
float mieScattering, mieAbsorption;
vec3 rayleighScattering, ozoneAbsorption;