From d4c19a8ade2a2f2d8d6f5a2acea1f801170533c1 Mon Sep 17 00:00:00 2001
From: Syndamia <kamen@syndamia.com>
Date: Mon, 1 Jul 2024 15:26:42 +0300
Subject: [PATCH] [project-easy] Implemented semi-transparent refractions

---
 flake.lock      | 27 +++++++++++++++++++++++++++
 flake.nix       | 26 ++++++++++++++++++++++++++
 src/main.cpp    |  2 +-
 src/shading.cpp |  8 +++++++-
 src/shading.h   |  4 ++++
 5 files changed, 65 insertions(+), 2 deletions(-)
 create mode 100644 flake.lock
 create mode 100644 flake.nix

diff --git a/flake.lock b/flake.lock
new file mode 100644
index 0000000..25db693
--- /dev/null
+++ b/flake.lock
@@ -0,0 +1,27 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1716061101,
+        "narHash": "sha256-H0eCta7ahEgloGIwE/ihkyGstOGu+kQwAiHvwVoXaA0=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "e7cc61784ddf51c81487637b3031a6dd2d6673a2",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixos-23.11",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/flake.nix b/flake.nix
new file mode 100644
index 0000000..d0a99fd
--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,26 @@
+# Този файл, заедно с flake.lock са си за моета система, да имам копие ако случайно изтрия нещо
+{
+  description = "hexray raytracer in FMI elective";
+
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs/nixos-23.11";
+  };
+
+  outputs = inputs:
+  let
+    pkgs = inputs.nixpkgs.legacyPackages."x86_64-linux";
+  in {
+    devShells."x86_64-linux".default = pkgs.mkShell {
+      nativeBuildInputs = with pkgs; [
+        cmake
+        pkg-config
+      ];
+
+      buildInputs = with pkgs; [
+        SDL2
+        openexr_3
+        zlib
+      ];
+    };
+  };
+}
diff --git a/src/main.cpp b/src/main.cpp
index fdca0f5..865a271 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -525,7 +525,7 @@ void renderThreadEntry() {
 	}
 }
 
-const char* DEFAULT_SCENE = "data/simple.hexray";
+const char* DEFAULT_SCENE = "data/beer.hexray";
 
 int main(int argc, char** argv)
 {
diff --git a/src/shading.cpp b/src/shading.cpp
index 94c417f..3d63dad 100644
--- a/src/shading.cpp
+++ b/src/shading.cpp
@@ -216,19 +216,25 @@ inline std::optional<Vector> refract(const Vector& i, const Vector& n, float ior
 Color Refraction::computeColor(const Ray& ray, const IntersectionInfo& info)
 {
 	std::optional<Vector> refr;
+	double transmittance = 1.0;
 	if (dot(ray.dir, info.norm) < 0) {
 		// entering the geometry
 		refr = refract(ray.dir, info.norm, 1 / ior);
 	} else {
 		// leaving the geometry
 		refr = refract(ray.dir, -info.norm, ior);
+
+		// Beer-Lambert law
+		double depth = (ray.start - info.ip).length();
+		// If absorption = 0; then transmittance = 1;
+		transmittance = exp(-1.0 * absorption * depth);
 	}
 	if (!refr) return Color(0, 0, 0);
 	Ray newRay = ray;
 	newRay.start = info.ip - faceforward(ray.dir, info.norm) * 0.000001;
 	newRay.dir = refr.value();
 	newRay.depth++;
-	return raytrace(newRay) * refrColor;
+	return raytrace(newRay) * refrColor * transmittance + insideColor * (1.0 - transmittance);
 }
 
 Color Refraction::eval(const IntersectionInfo& x, const Vector& w_in, const Vector& w_out)
diff --git a/src/shading.h b/src/shading.h
index 3a00527..005f203 100644
--- a/src/shading.h
+++ b/src/shading.h
@@ -148,6 +148,8 @@ class Refraction: public Shader {
 public:
 	Color refrColor = Color(0.95f, 0.95f, 0.95f);
 	double ior = 1.33;
+	Color insideColor = Color(0.0, 0.0, 0.0);
+	double absorption = 0.0;
 	virtual Color computeColor(const Ray& ray, const IntersectionInfo& info) override;
 	// from BRDF:
 	Color eval(const IntersectionInfo& x, const Vector& w_in, const Vector& w_out) override;
@@ -160,6 +162,8 @@ public:
             refrColor = Color(multiplier, multiplier, multiplier);
         } else pb.getColorProp("refrColor", &refrColor);
 		pb.getDoubleProp("ior", &ior, 1e-6, 10);
+        pb.getColorProp("insideColor", &insideColor);
+        pb.getDoubleProp("absorption", &absorption);
 	}
 };
 
-- 
2.42.0