From bae05d4df55a39d95c3c23d00e5acca14f422e8f Mon Sep 17 00:00:00 2001
From: kappa <petarkapris@firemail.cc>
Date: Sat, 7 Oct 2023 17:17:09 +0200
Subject: [PATCH] Re-add Parallelepiped with materials

---
 .../graphics3d/solids/Parallelepiped.java     | 108 ++++++++++++++++++
 1 file changed, 108 insertions(+)
 create mode 100644 src/xyz/marsavic/gfxlab/graphics3d/solids/Parallelepiped.java

diff --git a/src/xyz/marsavic/gfxlab/graphics3d/solids/Parallelepiped.java b/src/xyz/marsavic/gfxlab/graphics3d/solids/Parallelepiped.java
new file mode 100644
index 0000000..f7473d7
--- /dev/null
+++ b/src/xyz/marsavic/gfxlab/graphics3d/solids/Parallelepiped.java
@@ -0,0 +1,108 @@
+package xyz.marsavic.gfxlab.graphics3d.solids;
+
+import xyz.marsavic.functions.interfaces.F1;
+import xyz.marsavic.geometry.Vector;
+import xyz.marsavic.gfxlab.Vec3;
+import xyz.marsavic.gfxlab.graphics3d.Hit;
+import xyz.marsavic.gfxlab.graphics3d.Material;
+import xyz.marsavic.gfxlab.graphics3d.Ray;
+import xyz.marsavic.gfxlab.graphics3d.Solid;
+
+public class Parallelepiped implements Solid {
+
+    private final Vec3 p; // starting vertex
+
+    private final Vec3[][][] vertices;
+    HalfSpace [] sides;
+
+    private final Vec3 a, b, c;
+
+    private Parallelepiped(Vec3 point, Vec3 aEdge, Vec3 bEdge, Vec3 cEdge, F1<Material, Vector> mapMaterial) {
+        this.p = point;
+        this.a = aEdge;
+        this.b = bEdge;
+        this.c = cEdge;
+
+        vertices = new Vec3[][][]
+                {{{p,       p.add(c)},        {p.add(b),        p.add(b).add(c)}},
+                {{p.add(a), p.add(a).add(c)}, {p.add(a).add(b), p.add(a).add(b).add(c)}}};
+        sides = new HalfSpace[6];
+        sides[0] = HalfSpace.pef(p, b, a, mapMaterial);
+        sides[1] = HalfSpace.pef(p.add(c), a, b, mapMaterial);
+        sides[2] = HalfSpace.pef(p, a, c, mapMaterial);
+        sides[3] = HalfSpace.pef(p.add(b), c, a, mapMaterial);
+        sides[4] = HalfSpace.pef(p, c, b, mapMaterial);
+        sides[5] = HalfSpace.pef(p.add(a), b, c, mapMaterial);
+    }
+
+
+    public static Parallelepiped pabc(Vec3 p, Vec3 a, Vec3 b, Vec3 c, F1<Material, Vector> mapMaterial) {
+        return new Parallelepiped(p, a, b, c, mapMaterial);
+    }
+
+    public Vec3 p() {
+        return p;
+    }
+
+    public Vec3 a() {
+        return a;
+    }
+
+    public Vec3 b() {
+        return b;
+    }
+
+    public Vec3 c() {
+        return c;
+    }
+
+    public Vec3[][][] vertices() {
+        return vertices.clone();
+    }
+
+    private static boolean pointOnParallelogram(Vec3 p, Vec3 e, Vec3 f) {
+        // we solve p as a linear combination of a*e+b*f, then check if this combination is in
+        // 0<=a<=1 and 0<=b<=1
+        double D = e.lengthSquared() * f.lengthSquared() - e.dot(f)*e.dot(f);
+        if (D == 0)
+            return false;
+        // System determinant
+        double Da = p.dot(e)*f.lengthSquared() - p.dot(f)*e.dot(f);
+        // a's determinant
+        double Db = e.lengthSquared()*p.dot(f) - e.dot(f)*p.dot(e);
+        double a = Da/D;
+        // a's determinant
+        double b = Db/D;
+        // b's determinant
+        return a >= 0 && a <= 1 && b >= 0 && b <= 1;
+    }
+
+
+    @Override
+    public Hit firstHit(Ray ray, double afterTime) {
+        Hit[] planeHits = new Hit[6];
+
+        for (int i = 0; i < 6; i++) {
+            planeHits[i] = sides[i].firstHit(ray, afterTime);
+            if (planeHits[i] == null) {
+                continue;
+            }
+            Vec3 rayPlaneIntersect = ray.at(planeHits[i].t());
+            if (!pointOnParallelogram(rayPlaneIntersect.sub(sides[i].p()), sides[i].e(), sides[i].f())) {
+                planeHits[i] = null;
+            }
+        }
+
+        double minT = Hit.t(null); // Positive infinity
+        int minI = 0;
+        for (int i = 0; i < 6; i++) {
+            if (Hit.t(planeHits[i]) < minT) {
+                minT = Hit.t(planeHits[i]);
+                minI = i;
+            }
+        }
+
+        return planeHits[minI];
+    }
+
+}