1 files changed, 37 insertions, 0 deletions
diff --git a/src/4dshapes/4dsphere.cpp b/src/4dshapes/4dsphere.cpp
new file mode 100644
index 0000000..4ebe2ba
--- /dev/null
+++ b/src/4dshapes/4dsphere.cpp
@@ -0,0 +1,37 @@
+#include "raytracer/raytracer.h"
+
+// vector operations on 4d vectors,
+// reference: https://hollasch.github.io/ray4/Four-Space_Visualization_of_4D_Objects.html#chapter5
+
+bool HitSphere(RenderShapeData object, glm::vec4 rayOrigin, glm::vec4 rayDirection, glm::vec4 inter) {
+    float bb;
+    glm::vec4 cdir;
+    float rad;
+    float t1, t2;
+
+    cdir = object.ctm * glm::vec4(0.f,0.f,0.f,1.f) - rayOrigin;
+    bb = glm::dot(cdir, rayDirection);
+    rad = (bb * bb) - glm::dot(cdir, cdir) + 0.25f;
+
+    if (rad < 0.0) {
+        return false;
+    }
+
+    rad = sqrt(rad);
+    t2 = bb - rad;
+    t1 = bb + rad;
+
+    if ((t1 < 0.0) || ((t2 > 0.0) && (t2 < t1))) {
+        t1 = t2;
+    }
+
+    if (t1 <= 0.0) {
+        return false;
+    }
+
+    if (inter != glm::vec4(0.f,0.f,0.f, 1.f)) {
+        inter = rayOrigin + t1 * rayDirection;
+    }
+
+    return true;
+}
+\ No newline at end of file