Implenting volume

constantMedium.h

@@ -0,0 +1,65 @@
+#ifndef CONSTANT_MEDIUM_H
+#define CONSTANT_MEDIUM_H
+
+#include "rayTracer.h"
+#include "hittable.h"
+#include "material.h"
+#include "texture.h"
+
+class constantMedium : public hittable {
+    public:
+        constantMedium(shared_ptr<hittable> boundary, double density, shared_ptr<texture> tex): boundary(boundary), negativeInvDensity(-1/density), phaseFunction(make_shared<isotropic>(tex)) {}
+
+        constantMedium(shared_ptr<hittable> boundary, double density, const colour& albedo) : boundary(boundary), negativeInvDensity(-1 / density), phaseFunction(make_shared<isotropic>(albedo)) {}
+
+        bool hit(const ray& r, interval rayT, hitRecord& rec) const override {
+            // Print occasional samples when debugging. To enable, set enableDebug true;
+            const bool enableDebug = false;
+            const bool debugging = enableDebug && randomDouble() < 0.00001;
+
+            hitRecord rec1, rec2;
+
+            if (!boundary->hit(r, interval::universe, rec1)) return false;
+
+            if (!boundary->hit(r, interval(rec1.t+0.0001, infinity), rec2)) return false;
+
+            if (debugging) std::clog << "\ntMin=" << rec1.t << ", tMax=" << rec2.t << '\n';
+
+            if (rec1.t < rayT.min) rec1.t = rayT.min;
+            if (rec2.t > rayT.max) rec2.t = rayT.max;
+
+            if (rec1.t >= rec2.t) return false;
+
+            if (rec1.t < 0) rec1.t = 0;
+
+            auto rayLength = r.direction().length();
+            auto distanceInsideBoundary = (rec2.t - rec1.t) * rayLength;
+            auto hitDistance = negativeInvDensity * log(randomDouble());
+
+            if (hitDistance > distanceInsideBoundary) return false;
+
+            rec.t = rec1.t + hitDistance / rayLength;
+            rec.p = r.at(rec.t);
+
+            if (debugging) {
+                std::clog << "hitDistance = " << hitDistance << '\n' << "rec.t = " << rec.t << '\n' << "rec.p = " << rec.p << '\n';
+            }
+
+            rec.normal = vec3(1, 0, 0); // arbitrary
+            rec.frontFace = true;       // also abritrary 
+            rec.mat = phaseFunction;
+
+            return true;
+        }
+
+        aabb boundingBox() const override {
+            return boundary->boundingBox();
+        }
+
+    private: 
+        shared_ptr<hittable> boundary; 
+        double negativeInvDensity;
+        shared_ptr<material> phaseFunction;
+};
+
+#endif