2 files changed, 14 insertions, 0 deletions
diff --git a/src/mbgl/map/transform_state.cpp b/src/mbgl/map/transform_state.cpp
index f052e30a6b..4606e3eece 100644
--- a/src/mbgl/map/transform_state.cpp
+++ b/src/mbgl/map/transform_state.cpp
@@ -385,4 +385,16 @@ void TransformState::setScalePoint(const double newScale, const ScreenCoordinate
     Cc = Projection::worldSize(scale) / util::M2PI;
 }
 
+float TransformState::getCameraToTileDistance(const UnwrappedTileID& tileID) const {
+    mat4 projectionMatrix;
+    getProjMatrix(projectionMatrix);
+    mat4 tileProjectionMatrix;
+    matrixFor(tileProjectionMatrix, tileID);
+    matrix::multiply(tileProjectionMatrix, projectionMatrix, tileProjectionMatrix);
+    vec4 tileCenter = {{util::tileSize / 2, util::tileSize / 2, 0, 1}};
+    vec4 projectedCenter;
+    matrix::transformMat4(projectedCenter, tileCenter, tileProjectionMatrix);
+    return projectedCenter[3];
+}
+
 } // namespace mbgl
diff --git a/src/mbgl/map/transform_state.hpp b/src/mbgl/map/transform_state.hpp
index e6464aeacc..f35f570549 100644
--- a/src/mbgl/map/transform_state.hpp
+++ b/src/mbgl/map/transform_state.hpp
@@ -86,6 +86,8 @@ public:
         return !size.isEmpty() && (scale >= min_scale && scale <= max_scale);
     }
 
+    float getCameraToTileDistance(const UnwrappedTileID&) const;
+
 private:
     bool rotatedNorth() const;
     void constrain(double& scale, double& x, double& y) const;