1 files changed, 19 insertions, 0 deletions
diff --git a/src/mbgl/util/interpolate.cpp b/src/mbgl/util/interpolate.cpp
new file mode 100644
index 0000000000..306a5c6630
--- /dev/null
+++ b/src/mbgl/util/interpolate.cpp
@@ -0,0 +1,19 @@
+#include <mbgl/util/interpolate.hpp>
+
+#include <cmath>
+
+namespace mbgl {
+namespace util {
+
+float interpolationFactor(float base, Range<float> range, float z) {
+    const float zoomDiff = range.max - range.min;
+    const float zoomProgress = z - range.min;
+    if (base == 1.0f) {
+        return zoomProgress / zoomDiff;
+    } else {
+        return (std::pow(base, zoomProgress) - 1) / (std::pow(base, zoomDiff) - 1);
+    }
+}
+
+} // namespace util
+} // namespace mbgl