Added const to the two draw_sample methods that don't require the RNG

include/eos/morphablemodel/MorphableModel.hpp

@@ -150,7 +150,7 @@ public:
 	 * @param[in] color_coefficients The PCA coefficients used to generate the vertex colouring.
 	 * @return A model instance with given coefficients.
 	 */
-	render::Mesh draw_sample(std::vector<float> shape_coefficients, std::vector<float> color_coefficients)
+	render::Mesh draw_sample(std::vector<float> shape_coefficients, std::vector<float> color_coefficients) const
 	{
 		assert(shape_model.get_data_dimension() == color_model.get_data_dimension() || !has_color_model()); // The number of vertices (= model.getDataDimension() / 3) has to be equal for both models, or, alternatively, it has to be a shape-only model.
 

include/eos/morphablemodel/PcaModel.hpp

@@ -163,7 +163,7 @@ public:
 	 * @param[in] coefficients The PCA coefficients used to generate the sample.
 	 * @return A model instance with given coefficients.
 	 */
-	cv::Mat draw_sample(std::vector<float> coefficients)
+	cv::Mat draw_sample(std::vector<float> coefficients) const
 	{
 		// Fill the rest with zeros if not all coefficients are given:
 		if (coefficients.size() < get_num_principal_components()) {