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cloud shadow fixes and improvements #89

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2c94642
fix matrices
huj31415 Jun 21, 2026
8b8b5e0
cloud shadow temporal reprojection
huj31415 Jun 21, 2026
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1 change: 1 addition & 0 deletions shaders/lib/universal/SSBO.glsl
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Original file line number Diff line number Diff line change
Expand Up @@ -18,5 +18,6 @@ layout(std430, binding = 1) SSBO_DECLARED_TPYE buffer ExposureData {
layout(std430, binding = 2) SSBO_DECLARED_TPYE buffer CloudData {
mat4 shadowViewProj;
mat4 shadowViewProjInv;
mat4 prevShadowViewProj;
vec2 upscaleJitter;
} cloud;
17 changes: 13 additions & 4 deletions shaders/lib/utility/Matrix.glsl
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Original file line number Diff line number Diff line change
Expand Up @@ -20,8 +20,17 @@ mat4 BuildOrthoMat(float width, float height, float near, float far) {
return mat4(
-2.0 * rw, 0.0, 0.0, 0.0,
0.0, -2.0 * rh, 0.0, 0.0,
0.0, 0.0, 2.0 * rd, 0.0,
0.0, 0.0, (near + far) * rd, 1.0
0.0, 0.0, 2.0 * rd, (near + far) * rd,
0.0, 0.0, 0.0, 1.0
);
}

mat4 BuildInvOrthoMat(float width, float height, float near, float far) {
return mat4(
-0.5 * width, 0.0, 0.0, 0.0,
0.0, -0.5 * height, 0.0, 0.0,
0.0, 0.0, 0.5 * (far - near), 0.5 * (near + far),
0.0, 0.0, 0.0, 1.0
);
}

Expand All @@ -32,8 +41,8 @@ mat4 BuildPerspectiveMat(float fov, float aspect, float near, float far) {
return mat4(
f / aspect, 0.0, 0.0, 0.0,
0.0, f, 0.0, 0.0,
0.0, 0.0, (near + far) * rd, -1.0,
0.0, 0.0, near * far * rd * 2.0, 0.0
0.0, 0.0, (near + far) * rd, near * far * rd * 2.0,
0.0, 0.0, -1.0, 0.0
);
}

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48 changes: 33 additions & 15 deletions shaders/program/prepare/GenCloudShadow.comp
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Original file line number Diff line number Diff line change
@@ -1,10 +1,10 @@
/*
--------------------------------------------------------------------------------

Revelation Shaders
Revelation Shaders

Copyright (C) 2026 HaringPro
Apache License 2.0
Copyright (C) 2026 HaringPro
Apache License 2.0

--------------------------------------------------------------------------------
*/
Expand Down Expand Up @@ -37,17 +37,22 @@ writeonly uniform image2D cloudShadowImg;
#include "/lib/atmosphere/Common.glsl"
#include "/lib/atmosphere/clouds/Shape.glsl"

const float windAngle = radians(CLOUD_LOW_WIND_ANGLE);
const vec3 windDir = vec3(cos(windAngle), 0.5, sin(windAngle));
const vec3 windVelocity = windDir * CLOUD_LOW_WIND_SPEED;

//======// Main //================================================================================//
void main() {
ivec2 tid = ivec2(gl_GlobalInvocationID.xy);
ivec2 tid = ivec2(gl_GlobalInvocationID.xy);
const vec2 rSize = rcp(textureSize(cloudShadowTex, 0));

// Checkerboard render cloud shadow map
ivec2 offset = checkerboardOffset2x2[frameCounter & 3];
if ((tid & 1) == offset || historyReset) {
float dither = BlueNoise(tid, frameCounter);
// Checkerboard render cloud shadow map
ivec2 offset = checkerboardOffset2x2[frameCounter & 3];
if ((tid & 1) == offset || historyReset) {
float dither = BlueNoise(tid, frameCounter);

vec2 uv = (vec2(tid) + dither) * rcp(textureSize(cloudShadowTex, 0));
vec3 rayPos = SetupCloudShadowPos(uv) + atmosphereViewPos;
vec2 uv = (vec2(tid) + 0.5) * rSize;
vec3 rayPos = SetupCloudShadowPos(uv + (dither - 0.5) * rSize) + atmosphereViewPos;

// Increase steps for lower elevation
float steps = float(CLOUD_SHADOW_SAMPLES) * (2.0 - shadowDirWorld.y);
Expand All @@ -59,6 +64,8 @@ void main() {
rayPos += shadowDirWorld * intersection.x;
rayPos += rayStep * fract(dither + PHI);

vec3 cloudPos = rayPos - atmosphereViewPos + shadowDirWorld * dot(intersection, vec2(0.5));

float extinction = 0.0;
const float threshold = -log2(cloudMinTransmittance) / cumulusExtinction;

Expand All @@ -78,10 +85,21 @@ void main() {
float strength = linearstep(0.02, 0.05, shadowDirWorld.y) * sqrt(CLOUD_SHADOW_STRENGTH);
float cloudShadow = oms(strength) + transmittance * strength;

// Accumulate
float weight = rcp(min(frameCounter, 32) * float(!historyReset) + 1.0);
cloudShadow = mix(texelFetch(cloudShadowTex, tid, 0).x, cloudShadow, weight);
// Reproject and accumulate
vec3 motionVector = -windVelocity;
motionVector *= global.worldTimeDiff * 0.05;
motionVector += cameraMovement;
vec2 prevUV = transMAD(cloud.prevShadowViewProj, cloudPos).xy;
prevUV *= rcp(length(prevUV) * 0.5 + 0.5);
prevUV = prevUV * 0.5 + 0.5;

vec2 prevValue = textureLod(cloudShadowTex, prevUV, 0).xy;
float frameIdx = min(fma(prevValue.y, 256.0, 1.0), 16.0);
if (saturate(prevUV) == prevUV && frameIdx > 2.0 && !historyReset) {
float weight = rcp(frameIdx);
cloudShadow = mix(prevValue.x, cloudShadow, weight);
}

imageStore(cloudShadowImg, tid, vec4(cloudShadow));
}
imageStore(cloudShadowImg, tid, vec4(cloudShadow, frameIdx * rcp(256.0), 0.0, 0.0));
}
}
9 changes: 6 additions & 3 deletions shaders/program/prepare/UpdateSSBO.comp
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Expand Up @@ -36,6 +36,9 @@ const ivec3 workGroups = ivec3(1, 1, 1);

#include "/lib/universal/Random.glsl"

const mat4 shadowProj = BuildOrthoMat(CLOUD_SHADOW_DISTANCE * 32.0, CLOUD_SHADOW_DISTANCE * 32.0, 0.0, cumulusTopRadius);
const mat4 shadowInvProj = BuildInvOrthoMat(CLOUD_SHADOW_DISTANCE * 32.0, CLOUD_SHADOW_DISTANCE * 32.0, 0.0, cumulusTopRadius);

//======// Main //================================================================================//
void main() {
// Compute illuminance
Expand All @@ -51,9 +54,9 @@ void main() {

#ifdef CLOUDS
#ifdef CLOUD_SHADOWS
mat4 projMat = BuildOrthoMat(CLOUD_SHADOW_DISTANCE * 32.0, CLOUD_SHADOW_DISTANCE * 32.0, 0.0, cumulusTopRadius);
cloud.shadowViewProj = projMat * shadowModelView;
cloud.shadowViewProjInv = inverse(cloud.shadowViewProj);
cloud.prevShadowViewProj = cloud.shadowViewProj;
cloud.shadowViewProj = shadowProj * shadowModelView;
cloud.shadowViewProjInv = shadowModelViewInverse * shadowInvProj;
#endif

cloud.upscaleJitter = Halton23(frameCounter + 211);
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2 changes: 1 addition & 1 deletion shaders/shaders.properties
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Expand Up @@ -228,7 +228,7 @@ image.cloudOriginImg = cloudOriginTex RGBA RGBA16F HALF_FLOAT false true 0.333
image.cloudOriginImg = cloudOriginTex RGBA RGBA16F HALF_FLOAT false true 0.25 0.25
#endif

image.cloudShadowImg = cloudShadowTex RED R8 UNSIGNED_BYTE false false 512 512
image.cloudShadowImg = cloudShadowTex RG RG8 UNSIGNED_BYTE false false 512 512

# image.envBRDFImg = envBRDFTex RG RG16F HALF_FLOAT false false 256 256

Expand Down