Added simple volume generation into sphere.h for debugging

src/objs/sphere.h

@@ -20,4 +20,62 @@ struct Sphere {
         t = -b - h;
         return true;
     }
-};
+};
+
+// A function to generate two concentric spherical shells
+__host__ void generateVolume(float* hostVolume, int volW, int volH, int volD) {
+    int cx = volW / 2;
+    int cy = volH / 2;
+    int cz = volD / 2;
+    float maxRadius = static_cast<float>(volW) * 0.5f;
+
+    // Let's define two shells:
+    float shell1Inner = 0.2f * maxRadius;
+    float shell1Outer = 0.3f * maxRadius;
+    float shell2Inner = 0.4f * maxRadius;
+    float shell2Outer = 0.5f * maxRadius;
+
+    // Intensities
+    float shell1Intensity = 0.8f;
+    float shell2Intensity = 0.6f;
+
+    for (int z = 0; z < volD; ++z) {
+        for (int y = 0; y < volH; ++y) {
+            for (int x = 0; x < volW; ++x) {
+                float dx = (float)(x - cx);
+                float dy = (float)(y - cy);
+                float dz = (float)(z - cz);
+                float dist = sqrtf(dx*dx + dy*dy + dz*dz);
+
+                float intensity = 0.0f;
+
+                // Shell 1
+                if (dist >= shell1Inner && dist <= shell1Outer) {
+                    float mid = 0.5f * (shell1Inner + shell1Outer);
+                    if (dist < mid) {
+                        float inFactor = (dist - shell1Inner) / (mid - shell1Inner);
+                        intensity += shell1Intensity * inFactor;
+                    } else {
+                        float outFactor = (shell1Outer - dist) / (shell1Outer - mid);
+                        intensity += shell1Intensity * outFactor;
+                    }
+                }
+
+                // Shell 2
+                if (dist >= shell2Inner && dist <= shell2Outer) {
+                    float mid = 0.5f * (shell2Inner + shell2Outer);
+                    if (dist < mid) {
+                        float inFactor = (dist - shell2Inner) / (mid - shell2Inner);
+                        intensity += shell2Intensity * inFactor;
+                    } else {
+                        float outFactor = (shell2Outer - dist) / (shell2Outer - mid);
+                        intensity += shell2Intensity * outFactor;
+                    }
+                }
+
+                if (intensity > 1.0f) intensity = 1.0f;
+                    hostVolume[z * volW * volH + y * volW + x] = intensity;
+            }
+        }
+    }
+}