Clouds now interacting with lights, but especially sunlight is still buggy

fancy1.cpp

@@ -31,9 +31,11 @@ int main()
     scene.setBackgroundColor(Color(0.529f, 0.808f, 0.922f));
 
     // Add lights
-    auto mainLight = std::make_shared<SunLight>(Vector3d(-1.0f, -0.5f, -1.0f), 10.0f);
+    auto mainLight = std::make_shared<SunLight>(Vector3d(-1.0f, -0.5f, -1.0f), 10.0f, Color(1, 0.79f, 0.62f));
     scene.add(mainLight);
-    scene.add(std::make_shared<AmbientLight>(0.3f));
+//    scene.add(std::make_shared<AmbientLight>(0.3f));
+//    auto light = std::make_shared<PointLight>(Vector3d(25.0f, 10.0f, 25.0f), 100.0f);
+//    scene.add(light);
 
     // Add the bus
 //    auto busShader = std::make_shared<ToneShader>(mainLight);
@@ -54,11 +56,8 @@ int main()
     // Add box for volume shader
     auto cloudSettings = CloudSettings();
     cloudSettings.scale = 15.0f;
-    cloudSettings.densityIntensity = 10.0f;
-    cloudSettings.densityTreshold = 0.49f;
-    cloudSettings.densityAbsorption = 0.9f;
     auto cloudShader = std::make_shared<CloudShader>(cloudSettings);
-    scene.add(std::make_shared<Box>(Vector3d(20.0f, 8.0f, 20.0f), Vector3d(50.0f, 5.0f, 50.0f), cloudShader));
+    scene.add(std::make_shared<Box>(Vector3d(20.0f, 10.0f, 20.0f), Vector3d(50.0f, 10.0f, 50.0f), cloudShader));
 
     // build the tree
     scene.buildTree();

shader/cloudshader.cpp

@@ -36,25 +36,28 @@ Color CloudShader::shade(const Scene &scene, const Ray &ray) const
     float stepLength = cloudLength / noiseSamples;
 
     // Step through cloud
-    float transmittance = 1.0f;
+    float transmittance = 1;
-    Color cloudColor = Color(1, 1, 1);
+    Color cloudColor = Color(0, 0, 0);
     for (int i = 0; i < noiseSamples; ++i)
     {
         // Get sample point
-        Vector3d samplePoint = hitPoint + i * stepLength * ray.direction;
+        Vector3d lengthDirection = i * stepLength * ray.direction;
+        Vector3d samplePoint = hitPoint + lengthDirection;
 
         // Get data at point
         float sampleDensity = getCloudDensity(samplePoint) * stepLength;
 
-        if (sampleDensity > REFR_EPS) {
+        if (sampleDensity > 0)
-            cloudColor += lightMarch(scene, samplePoint, ray);
+        {
+            cloudColor += lightMarch(scene, samplePoint, lengthDirection) * stepLength * sampleDensity;
         }
 
-        transmittance *= exp(-sampleDensity * stepLength * settings.densityAbsorption);
+        transmittance *= exp(-sampleDensity * stepLength * settings.lightAbsorptionThroughCloud);
-        if (transmittance <= TRANSMITTANCE_BREAK) break; // No need to continue
+
+        if (transmittance < TRANSMITTANCE_BREAK) break; // Cloud is effectively opaque
     }
 
-    return background * transmittance + (1.0f - transmittance) * cloudColor;
+    return background * transmittance + cloudColor;
 }
 
 bool CloudShader::isTransparent() const
@@ -76,40 +79,60 @@ float CloudShader::getCloudDensity(Vector3d point) const
 
     // Threshold
     // TODO: Smooth out!
-    density = std::max(0.0f, density - settings.densityTreshold) * settings.densityIntensity;
+    density = std::max(0.0f, density + settings.densityOffset) * settings.densityIntensity;
 
     return density;
 }
 
-Color CloudShader::lightMarch(const Scene &scene, Vector3d position, const Ray &ray) const
+Color CloudShader::lightMarch(const Scene &scene, Vector3d currentInCloudPosition, Vector3d lengthDistance) const
 {
     Color cloudColor;
 
     // For alle lights
     for (const auto &light: scene.lights())
     {
-        auto illumination = light->illuminate(scene, position);
+        Ray ray = Ray(currentInCloudPosition - lengthDistance, normalized(lengthDistance));
+        ray.length = length(lengthDistance);
+        auto illumination = light->illuminate(scene, ray);
 
         // Handle ambient lights
-        if (illumination.distance == 0.0f) {
+        if (illumination.distance == 0.0f)
+        {
             cloudColor += illumination.color;
             continue;
         }
 
         // Light ray
         Ray lightRay;
-        lightRay.origin = position;
+        lightRay.origin = currentInCloudPosition;
         lightRay.direction = illumination.direction;
         lightRay.length = 0;    // Starting in cloud itself
 
-        Color transparency = this->transparency(scene, lightRay, illumination.distance);
+        float density = this->rayDensity(lightRay, illumination.distance);
-        cloudColor += transparency * illumination.color;
+        density *= settings.lightAbsorptionTowardsLight;
+
+        // Proper light calculation
+        float transmittance = exp(-density) * (1 - exp(-density * 2));
+        float scatter = scatterFactor(normalized(lengthDistance), illumination.direction);
+
+        float factor = settings.darknessThreshold + (scatter * transmittance) * (1 - settings.darknessThreshold);   // (transmittance * scatter)
+        cloudColor += factor * illumination.color;
     }
 
     return cloudColor;
 }
 
 Color CloudShader::transparency(const Scene &scene, const Ray &ray, float maxLength) const
+{
+    float density = rayDensity(ray, maxLength);
+
+    float transmittance = exp(-density * settings.shadowLightAbsorption);
+    transmittance = 1 - (1 - transmittance) * settings.shadowIntensity;
+
+    return Color(1, 1, 1) * transmittance;
+}
+
+float CloudShader::rayDensity(const Ray &ray, float maxLength) const
 {
     Vector3d startPoint = ray.origin + ray.direction * (ray.length + 0.0001f);
 
@@ -122,19 +145,20 @@ Color CloudShader::transparency(const Scene &scene, const Ray &ray, float maxLen
     cloudRay.primitive = nullptr;
 
     // Get out of cloud primitive first
-    if (ray.primitive != nullptr && !ray.primitive->intersect(cloudRay) || cloudRay.length == INFINITY || cloudRay.length <= 0)
+    if (ray.primitive != nullptr && !ray.primitive->intersect(cloudRay) || cloudRay.length == INFINITY ||
+        cloudRay.length <= 0)
     {
-        // Something went wrong
+        // Something went wrong => No density
-        return Color(1, 1, 1);
+        return 0;
     }
     cloudLength = std::min(cloudRay.length, maxLength - ray.length);
 
     // Calculate step length
     int noiseSamples = settings.lightSamples;
-    float stepLength = cloudLength / noiseSamples;
+    float stepLength = cloudLength / (float) noiseSamples;
 
     // Step through cloud
-    float transmittance = 1.0f;
+    float density = 1.0f;
     for (int i = 0; i < noiseSamples; ++i)
     {
         // Get sample point
@@ -143,11 +167,47 @@ Color CloudShader::transparency(const Scene &scene, const Ray &ray, float maxLen
         // Get data at point
         float sampleDensity = getCloudDensity(samplePoint) * stepLength;
 
-        transmittance *= exp(-sampleDensity * stepLength);
+        density += sampleDensity * stepLength;
-        if (transmittance <= TRANSMITTANCE_BREAK) break; // No need to continue
     }
 
-    transmittance = 1 - (1 - transmittance) * settings.shadowIntensity;
+    // If there is length left, check if it is in the cloud recursively
+    if (cloudLength < maxLength - ray.length)
+    {
+        Vector3d endPoint = startPoint + (cloudLength + REFR_EPS) * ray.direction;
+        Ray recursiveRay = cloudRay;
+        recursiveRay.origin = endPoint;
+        recursiveRay.length = 0;
+        recursiveRay.primitive = nullptr;
 
-    return Color(1, 1, 1) * transmittance;
+        if (ray.primitive != nullptr && ray.primitive->intersect(recursiveRay) && recursiveRay.length > 0)
+        {
+            density += rayDensity(recursiveRay, maxLength - (cloudLength + REFR_EPS));
+        }
+    }
+
+    return density;
+}
+
+float CloudShader::scatterFactor(Vector3d visualRay, Vector3d illuminationRay) const
+{
+    // The asymmetry parameter
+    float g = 0.7f;
+
+    // The angle between the visual and illumination rays
+    float cosTheta = dotProduct(visualRay, illuminationRay);
+
+    // The Dual-Lob Henyey-Greenstein function
+    float blend = .5;
+    float scatter = HenyeyGreenstein(cosTheta,g) * (1-blend) + HenyeyGreenstein(cosTheta,-g) * blend;
+
+    // Clamp the result to the range [0, 1]
+    scatter = std::max(std::min(scatter, 1.0f), 0.0f);
+
+    return scatter;
+}
+
+float CloudShader::HenyeyGreenstein(float cosTheta, float g) const
+{
+    float g2 = g * g;
+    return (1 - g2) / (4 * 3.1415f * pow(1 + g2 - 2 * g * (cosTheta), 1.5f));
 }

shader/cloudshader.h

@@ -8,18 +8,20 @@
 #include "common/noise/worleynoise.h"
 
 int const NOISE_SIZE = 128;
-int const TRANSMITTANCE_BREAK = 0.005f;  // If transmittance goes below this limit, the cloud is considered opaque
+float const TRANSMITTANCE_BREAK = 0.005f;  // If transmittance goes below this limit, the cloud is considered opaque
 
 struct CloudSettings
 {
     int densitySamples = 100;
-    int lightSamples = 20;
+    int lightSamples = 100;
     float scale = 10;
-    float densityTreshold = 0.55f;
+    float densityOffset = -0.55f;
-    float densityIntensity = 2.5f;
+    float densityIntensity = 7.0f;
-    float densityAbsorption = 2;
+    float darknessThreshold = 0.07f;
-    float darknessThreshold = 0.1f;
+    float shadowLightAbsorption = 2;
     float shadowIntensity = 0.8f;
+    float lightAbsorptionTowardsLight = 0.94f;
+    float lightAbsorptionThroughCloud = 0.85f;
 };
 
 class CloudShader : public Shader
@@ -41,7 +43,13 @@ private:
 
     float getCloudDensity(Vector3d point) const;
 
-    Color lightMarch(const Scene &scene, Vector3d position, const Ray &ray) const;
+    Color lightMarch(const Scene &scene, Vector3d currentInCloudPosition, Vector3d lengthDistance) const;
+
+    float rayDensity(const Ray &ray, float maxLength) const;
+
+    float scatterFactor(Vector3d visualRay, Vector3d illuminationRay) const;
+
+    float HenyeyGreenstein(float cosTheta, float g) const;
 };
 
 

shader/refractionshader.cpp

@@ -9,8 +9,11 @@ RefractionShader::RefractionShader(float indexInside, float indexOutside, Color
 Color RefractionShader::shade(Scene const &scene, Ray const &ray) const
 {
     // Circumvent getting environment map color into the mix
-    if (ray.getRemainingBounces() > 0)
+    if (ray.getRemainingBounces() <= 0)
     {
+        return Color(0.0f, 0.0f, 0.0f);
+    }
+
     // Get the normal of the primitive which was hit
     Vector3d normalVector = ray.normal;
 
@@ -58,8 +61,6 @@ Color RefractionShader::shade(Scene const &scene, Ray const &ray) const
 
     return hitColor * objectColor * lightRemaining;
 }
-    return Color(0.0f, 0.0f, 0.0f);
-}
 
 float RefractionShader::remainingLightIntensity(float distanceThroughObject) const
 {