diff --git a/simulation/include/pcl/simulation/range_likelihood.h b/simulation/include/pcl/simulation/range_likelihood.h
index 72d3e4b3079..39334f9030c 100644
--- a/simulation/include/pcl/simulation/range_likelihood.h
+++ b/simulation/include/pcl/simulation/range_likelihood.h
@@ -107,7 +107,7 @@ namespace pcl
                                        float &camera_fx_in,
                                        float &camera_fy_in,
                                        float &camera_cx_in,
-                                       float &camera_cy_in)
+                                       float &camera_cy_in) const
         {
           camera_width_in = camera_width_;
           camera_height_in = camera_height_;
@@ -124,23 +124,23 @@ namespace pcl
         void setSigma (double sigma_in){  sigma_ = sigma_in;	}
         void setFloorProportion (double floor_proportion_in){  floor_proportion_ = floor_proportion_in;}
 
-        int getRows () {return rows_;}
-        int getCols () {return cols_;}
-        int getRowHeight () {return row_height_;}
-        int getColWidth () {return col_width_;}
-        int getWidth () {return width_;}
-        int getHeight () {return height_;}
+        int getRows () const {return rows_;}
+        int getCols () const {return cols_;}
+        int getRowHeight () const {return row_height_;}
+        int getColWidth () const {return col_width_;}
+        int getWidth () const {return width_;}
+        int getHeight () const {return height_;}
 
         // Convenience function to return simulated RGB-D PointCloud
         // Two modes:
         // global=false - PointCloud is as would be captured by an RGB-D camera [default]
         // global=true  - PointCloud is transformed into the model/world frame using the camera pose
         void getPointCloud (pcl::PointCloud<pcl::PointXYZRGB>::Ptr pc,
-              bool make_global, const Eigen::Isometry3d & pose, bool organized = false);
+              bool make_global, const Eigen::Isometry3d & pose, bool organized = false) const;
 
         // Convenience function to return RangeImagePlanar containing
         // simulated RGB-D:
-        void getRangeImagePlanar (pcl::RangeImagePlanar &rip);
+        void getRangeImagePlanar (pcl::RangeImagePlanar &rip) const;
 
         // Add various types of noise to simulated RGB-D data
         void addNoise ();
@@ -156,19 +156,19 @@ namespace pcl
         setUseColor(bool use_color) { use_color_ = use_color; }
 
         const uint8_t*
-        getColorBuffer ();
+        getColorBuffer () const;
 
         const float*
-        getDepthBuffer ();
+        getDepthBuffer () const;
 
         const float*
-        getScoreBuffer ();
+        getScoreBuffer () const;
 
         float 
-        getZNear (){ return z_near_; }
+        getZNear () const { return z_near_; }
         
         float 
-        getZFar (){ return z_far_; }
+        getZFar () const { return z_far_; }
         
         void 
         setZNear (float z){ z_near_ = z; }
@@ -228,9 +228,10 @@ namespace pcl
         float z_near_;
         float z_far_;
 
-        bool depth_buffer_dirty_;
-        bool color_buffer_dirty_;
-        bool score_buffer_dirty_;
+        // For caching only, not part of observable state.
+        mutable bool depth_buffer_dirty_;
+        mutable bool color_buffer_dirty_;
+        mutable bool score_buffer_dirty_;
 	
 	int which_cost_function_;
 	double floor_proportion_;
diff --git a/simulation/src/range_likelihood.cpp b/simulation/src/range_likelihood.cpp
index dca919f0e5c..1b05e4c6537 100644
--- a/simulation/src/range_likelihood.cpp
+++ b/simulation/src/range_likelihood.cpp
@@ -651,7 +651,7 @@ void
 pcl::simulation::RangeLikelihood::getPointCloud (pcl::PointCloud<pcl::PointXYZRGB>::Ptr pc,
   bool make_global,
   const Eigen::Isometry3d & pose,
-  bool organized)
+  bool organized) const
 {
   // TODO: check if this works for for rows/cols >1  and for width&height != 640x480
   // i.e. multiple tiled images
@@ -762,7 +762,7 @@ pcl::simulation::RangeLikelihood::getPointCloud (pcl::PointCloud<pcl::PointXYZRG
 }
 
 void
-pcl::simulation::RangeLikelihood::getRangeImagePlanar(pcl::RangeImagePlanar &rip)
+pcl::simulation::RangeLikelihood::getRangeImagePlanar(pcl::RangeImagePlanar &rip) const
 {
   rip.setDepthImage (depth_buffer_,
     camera_width_,camera_height_, camera_fx_,camera_fy_,
@@ -1053,7 +1053,7 @@ RangeLikelihood::render (const std::vector<Eigen::Isometry3d, Eigen::aligned_all
 }
 
 const float*
-RangeLikelihood::getDepthBuffer ()
+RangeLikelihood::getDepthBuffer () const
 {
   if (depth_buffer_dirty_)
   {
@@ -1073,7 +1073,7 @@ RangeLikelihood::getDepthBuffer ()
 }
 
 const uint8_t*
-RangeLikelihood::getColorBuffer ()
+RangeLikelihood::getColorBuffer () const
 {
   // It's only possible to read the color buffer if it
   // was rendered in the first place.
@@ -1105,7 +1105,7 @@ RangeLikelihood::getColorBuffer ()
 
 // The scores are in score_texture_
 const float*
-RangeLikelihood::getScoreBuffer ()
+RangeLikelihood::getScoreBuffer () const
 {
   if (score_buffer_dirty_ && !compute_likelihood_on_cpu_)
   {