I am a cloud god now

fancy1.cpp

@@ -32,7 +32,8 @@ int main()
 //    scene.setBackgroundColor(Color(1, 0.79f, 0.62f) * 0.8f);
 
     // Add lights
-    auto mainLight = std::make_shared<SunLight>(Vector3d(-1.0f, -0.5f, -1.0f), 2.0f, Color(1,1,1));//Color(1, 0.79f, 0.62f));
+    // Alternate direction Vector3d(1.0f, -0.5f, 1.0f)
+    auto mainLight = std::make_shared<SunLight>(Vector3d(0, -1.0f, 0), 1.0f, Color(1,1,1));//Color(1, 0.79f, 0.62f));
     scene.add(mainLight);
 //    scene.add(std::make_shared<AmbientLight>(0.3f));
 //    auto light = std::make_shared<PointLight>(Vector3d(25.0f, 10.0f, 25.0f), 100.0f);
@@ -56,9 +57,8 @@ int main()
 
     // Add box for volume shader
     auto cloudSettings = CloudSettings();
-    cloudSettings.scale = 15.0f;
     auto cloudShader = std::make_shared<CloudShader>(cloudSettings);
-    scene.add(std::make_shared<Box>(Vector3d(20.0f, 10.0f, 20.0f), Vector3d(50.0f, 10.0f, 50.0f), cloudShader));
+    scene.add(std::make_shared<Box>(Vector3d(20.0f, 15.0f, 20.0f), Vector3d(70.0f, 10.0f, 70.0f), cloudShader));
 
     // build the tree
     scene.buildTree();
@@ -73,7 +73,7 @@ int main()
     // Render the scene
     SuperRenderer sr;
     sr.setSuperSamplingFactor(1);
-    sr.renderImage(scene, camera, 1024, 1024).save("result.png");
+    sr.renderImage(scene, camera, 256, 256).save("result.png");
 
     return 0;
 }

shader/cloudshader.cpp

@@ -1,3 +1,5 @@
+#include <cmath>
+#include <iostream>
 #include "cloudshader.h"
 #include "common/noise/cloudnoise.h"
 
@@ -32,34 +34,32 @@ Color CloudShader::shade(const Scene &scene, const Ray &ray) const
     if (cloudLength == 0.0f) return background; // No cloud or at edge
 
     // Calculate step length
-    int noiseSamples = settings.densitySamples;
+    float stepLength =  settings.densitySteps;
-    float stepLength = cloudLength / (float) noiseSamples;
+    int noiseSamples = std::floor(cloudLength / stepLength);
 
     // Step through cloud
-    float accumulatedDensity = 0.0f;
+    float transmittance = 1.0f;
     Color cloudColor = Color(0, 0, 0);
     for (int i = 0; i < noiseSamples; ++i)
     {
         // Get sample point
-        Vector3d lengthDirection = i * stepLength * ray.direction;
+        Vector3d lengthDirection = (float) i * stepLength * ray.direction;
         Vector3d samplePoint = hitPoint + lengthDirection;
 
         // Get data at point
-        float sampleDensity = getCloudDensity(samplePoint) * stepLength;
+        float sampleDensity = getCloudDensity(samplePoint, ray.primitive) * stepLength;
 
-        if (sampleDensity > 0)
+        if (sampleDensity <= 0)
         {
-            cloudColor += lightMarch(scene, samplePoint, lengthDirection, ray.primitive) * sampleDensity;
+            continue;
         }
 
-        accumulatedDensity += sampleDensity;
+        cloudColor += lightMarch(scene, samplePoint, lengthDirection, ray.primitive) * sampleDensity * transmittance;
+        transmittance *= calcBeer(sampleDensity * settings.lightAbsorptionThroughCloud);
+
+        if (transmittance < TRANSMITTANCE_BREAK) break;
     }
 
-    if (accumulatedDensity > 1)
-        cloudColor /= accumulatedDensity;
-
-    float transmittance = exp(-accumulatedDensity * settings.lightAbsorptionThroughCloud);
-
     return background * transmittance + cloudColor;
 }
 
@@ -74,17 +74,53 @@ CloudShader::CloudShader(const CloudSettings &settings) : settings(settings),
     cloudNoise.invert = true;
 }
 
-float CloudShader::getCloudDensity(Vector3d point) const
+float CloudShader::getCloudDensity(Vector3d point, Primitive const *primitive) const
 {
-    point /= settings.scale;
+    //! Requires the unscaled point
+    float edgeDensity = getEdgeDensity(point, primitive);
 
+    point /= settings.scale;
     float density = cloudNoise.getNoise(point);
 
     // Threshold
     // TODO: Smooth out!
     density = std::max(0.0f, density + settings.densityOffset) * settings.densityIntensity;
 
-    return density;
+    return density * edgeDensity;
+}
+
+float CloudShader::getEdgeDensity(const Vector3d &point, const Primitive *primitive) const
+{
+    if (primitive == nullptr)
+    {
+        return 1;
+    }
+
+    Vector3d size = Vector3d(0, 0, 0);
+    size.x = primitive->maximumBounds(0) - primitive->minimumBounds(0);
+    size.y = primitive->maximumBounds(1) - primitive->minimumBounds(1);
+    size.z = primitive->maximumBounds(2) - primitive->minimumBounds(2);
+
+    Vector3d center = Vector3d(0, 0, 0);
+    center.x = primitive->maximumBounds(0) + primitive->minimumBounds(0);
+    center.y = primitive->maximumBounds(1) + primitive->minimumBounds(1);
+    center.z = primitive->maximumBounds(2) + primitive->minimumBounds(2);
+    center /= 2;
+
+    Vector3d distance = point - center;
+    distance.x = std::abs(distance.x);
+    distance.y = std::abs(distance.y);
+    distance.z = std::abs(distance.z);
+
+    Vector3d distanceFromEdge = size / 2 - distance;
+    distanceFromEdge.x = std::max(0.0f, distanceFromEdge.x);
+    distanceFromEdge.y = std::max(0.0f, distanceFromEdge.y);
+    distanceFromEdge.z = std::max(0.0f, distanceFromEdge.z);
+
+    float fallOff = std::min(distanceFromEdge.x, std::min(distanceFromEdge.y, distanceFromEdge.z)) /
+                    settings.edgeFadeOffDistance;
+
+    return std::min(1.0f, fallOff);
 }
 
 Color CloudShader::lightMarch(const Scene &scene, Vector3d currentInCloudPosition, Vector3d lengthDistance,
@@ -107,43 +143,33 @@ Color CloudShader::lightMarch(const Scene &scene, Vector3d currentInCloudPositio
             continue;
         }
 
-        // Light ray
+        // Light ray from object to light
         Ray lightRay;
         lightRay.origin = currentInCloudPosition;
-        lightRay.direction = illumination.direction;
+        lightRay.direction = -illumination.direction;
         lightRay.primitive = cloudObject;
         lightRay.length = 0;    // Starting in cloud itself
 
         float density = this->rayDensity(lightRay, illumination.distance);
-        density *= settings.lightAbsorptionTowardsLight;
 
         // Proper light calculation
-        float transmittance = getDensityTransmittance(density);
+        float transmittance = calcBeer(density * settings.lightAbsorptionTowardsLight);
-        float scatter = scatterFactor(normalized(lengthDistance), illumination.direction);
 
-        float factor = transmittance;
+        transmittance *= phase(normalized(lengthDistance), lightRay.direction);
-        if (density > 0)
-        {
-            factor = settings.darknessThreshold +
-                     (1.0f - settings.darknessThreshold) * factor * scatter;
-        }
 
-        cloudColor += factor * illumination.color;
+        cloudColor += transmittance * illumination.color;
     }
 
-    return cloudColor;
+    float darknessFactor = settings.darknessThreshold +
-}
+                           (1.0f - settings.darknessThreshold);
-
+    return cloudColor * darknessFactor;
-float CloudShader::getDensityTransmittance(float density) const
-{
-    return exp(-density) * (1 - exp(-density * 2)) / 0.4f;
 }
 
 Color CloudShader::transparency(const Scene &scene, const Ray &ray, float maxLength) const
 {
     float density = rayDensity(ray, maxLength);
 
-    float transmittance = exp(-density * settings.shadowLightAbsorption);
+    float transmittance = calcBeer(density * settings.shadowLightAbsorption);
     transmittance = 1 - (1 - transmittance) * settings.shadowIntensity;
 
     return Color(1, 1, 1) * transmittance;
@@ -151,36 +177,38 @@ Color CloudShader::transparency(const Scene &scene, const Ray &ray, float maxLen
 
 float CloudShader::rayDensity(const Ray &ray, float maxLength) const
 {
-    Vector3d startPoint = ray.origin + ray.direction * (ray.length + 0.0001f);
+    Vector3d startPoint = ray.origin + ray.direction * (ray.length + REFR_EPS);
 
     // Determine length of cloud
-    Ray cloudRay = ray;
+    Ray cloudRay;
     cloudRay.origin = startPoint;
     cloudRay.length = INFINITY;
+    cloudRay.direction = ray.direction;
     cloudRay.primitive = nullptr;
 
     // Get out of cloud primitive first
     if (ray.primitive != nullptr && !ray.primitive->intersect(cloudRay) || cloudRay.length == INFINITY ||
         cloudRay.length <= 0)
     {
-        // Something went wrong => No density
+        // Assume ray started in cloud
-        return 0;
+        cloudRay.length = ray.length;
+        cloudRay.primitive = ray.primitive;
     }
     float cloudLength = std::min(cloudRay.length, maxLength - ray.length);
 
     // Calculate step length
-    int noiseSamples = settings.lightSamples;
+    float stepLength = settings.densitySteps;
-    float stepLength = cloudLength / (float) noiseSamples;
+    int noiseSamples = std::floor(cloudLength / stepLength);
 
     // Step through cloud
     float density = 0.0f;
     for (int i = 0; i < noiseSamples; ++i)
     {
         // Get sample point
-        Vector3d samplePoint = startPoint + i * stepLength * ray.direction;
+        Vector3d samplePoint = startPoint + (float) i * stepLength * ray.direction;
 
         // Get data at point
-        density += getCloudDensity(samplePoint) * stepLength;
+        density += getCloudDensity(samplePoint, ray.primitive) * stepLength;
     }
 
     // If there is length left, check if it is in the cloud recursively
@@ -201,26 +229,31 @@ float CloudShader::rayDensity(const Ray &ray, float maxLength) const
     return density;
 }
 
-float CloudShader::scatterFactor(Vector3d visualRay, Vector3d illuminationRay) const
+float CloudShader::phase(Vector3d visualRay, Vector3d illuminationRay) const
 {
-    // The asymmetry parameter
-    float g = settings.scatterWeight;
-
     // 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;
+    float phaseBlend = calcDualHenyeyGreenstein(cosTheta, settings.phaseA) * (1 - blend) +
+            calcDualHenyeyGreenstein(cosTheta, -settings.phaseB) * blend;
 
     // Clamp the result to the range [0, 1]
-    scatter = std::max(std::min(scatter, 1.0f), 0.0f);
+    phaseBlend = std::max(std::min(phaseBlend, 1.0f), 0.0f);
 
-    return scatter;
+    return settings.phaseOffset + phaseBlend * settings.phaseIntensity;
 }
 
-float CloudShader::HenyeyGreenstein(float cosTheta, float g) const
+float CloudShader::calcBeer(float d)
+{
+    float beer = std::exp(-d);
+    return beer;
+}
+
+
+float CloudShader::calcDualHenyeyGreenstein(float cosTheta, float g)
 {
     float g2 = g * g;
-    return (1 - g2) / (4 * 3.1415f * pow(1 + g2 - 2 * g * (cosTheta), 1.5f));
+    return (1 - g2) / (4 * 3.1415f * std::pow(1 + g2 - 2 * g * (cosTheta), 1.5f));
 }

shader/cloudshader.h

@@ -7,22 +7,25 @@
 #include "primitive/primitive.h"
 #include "common/noise/worleynoise.h"
 
-int const NOISE_SIZE = 128;
+int const NOISE_SIZE = 64;
-float const TRANSMITTANCE_BREAK = 0.005f;  // If transmittance goes below this limit, the cloud is considered opaque
+float const TRANSMITTANCE_BREAK = 0.0001f;  // If transmittance goes below this limit, the cloud is considered opaque
 
 struct CloudSettings
 {
-    int densitySamples = 100;
+    float densitySteps = .2f;   // .2f
-    int lightSamples = 100;
+    float scale = 30;   // 30
-    float scale = 10;
+    float densityOffset = -.55f;    // -.55f
-    float densityOffset = -0.57f;
+    float densityIntensity = 5.0f;  // 5.0f
-    float densityIntensity = 7.0f; // 7.0f
+    float darknessThreshold = .1f;  // .1f
-    float darknessThreshold = 0.1f;    // 0.07f
+    float shadowIntensity = .6f;    // .6f
-    float shadowIntensity = 0.6f;
+    float shadowLightAbsorption = 1;    // 1
-    float shadowLightAbsorption = 1;
+    float lightAbsorptionTowardsLight = 0.3f;   // .3f
-    float lightAbsorptionTowardsLight = 1.0f;
+    float lightAbsorptionThroughCloud = .8f;   // .8f   // How dark should the background be where the cloud is? Higher values mean darker background
-    float lightAbsorptionThroughCloud = 0.5f;
+    float phaseA = .5f; // .5f
-    float scatterWeight = 0.5f;
+    float phaseB = .3f; // .3f
+    float phaseOffset = .8f;    // .8f
+    float phaseIntensity = 1.0f;    // 1.0f
+    float edgeFadeOffDistance = .5f;    // .5f
 };
 
 class CloudShader : public Shader
@@ -32,6 +35,7 @@ public:
 
     // Shader functions
     Color shade(Scene const &scene, Ray const &ray) const;
+
     Color transparency(const Scene &scene, const Ray &ray, float maxLength) const override;
 
 private:
@@ -42,17 +46,20 @@ private:
 
     Noise cloudNoise;
 
-    float getCloudDensity(Vector3d point) const;
+    float getCloudDensity(Vector3d point, const Primitive *primitive = nullptr) const;
 
-    Color lightMarch(const Scene &scene, Vector3d currentInCloudPosition, Vector3d lengthDistance, const Primitive *cloudObject) const;
+    Color lightMarch(const Scene &scene, Vector3d currentInCloudPosition, Vector3d lengthDistance,
+                     const Primitive *cloudObject) const;
 
     float rayDensity(const Ray &ray, float maxLength) const;
 
-    float scatterFactor(Vector3d visualRay, Vector3d illuminationRay) const;
+    float phase(Vector3d visualRay, Vector3d illuminationRay) const;
 
-    float HenyeyGreenstein(float cosTheta, float g) const;
+    static float calcDualHenyeyGreenstein(float cosTheta, float g) ;
 
-    float getDensityTransmittance(float density) const;
+    static float calcBeer(float d) ;
+
+    float getEdgeDensity(const Vector3d &point, const Primitive *primitive) const;
 };