initial commit

cdf.h

@@ -0,0 +1,29 @@
+#pragma once
+
+#include "diffvg.h"
+
+DEVICE int sample(const float *cdf, int num_entries, float u, float *updated_u = nullptr) {
+    // Binary search the cdf
+    auto lb = 0;
+    auto len = num_entries - 1 - lb;
+    while (len > 0) {
+        auto half_len = len / 2;
+        auto mid = lb + half_len;
+        assert(mid >= 0 && mid < num_entries);
+        if (u < cdf[mid]) {
+            len = half_len;
+        } else {
+            lb = mid + 1;
+            len = len - half_len - 1;
+        }
+    }
+    lb = clamp(lb, 0, num_entries - 1);
+    if (updated_u != nullptr) {
+    	if (lb > 0) {
+    		*updated_u = (u - cdf[lb - 1]) / (cdf[lb] - cdf[lb - 1]);
+    	} else {
+    		*updated_u = u / cdf[lb];
+    	}
+    }
+    return lb;
+}