A Study On Nonphotorealistic Rendering Of Three-dimensional Trees With Chinese Ink Painting Style

Since the birth of computer graphics,the main goal is to obtain realistic graphics.With the improvement of computer hardware and software,researchers have been able to simulate most of the material and phenomena in nature.Then researchers turn to simulate the realistic drawing with the non-photorealistic rendering.As a result,it is not necessary to require realistic effect for painting,but more attention to art and emotional communication is focused on.In Chinese ink paintings,trees are often an important element in drawing scenes.Compared with the traditional objects,there are more complicated fractal structure for trees.So it is very important to promote the development and popularization of traditional culture by computer simulation.In this thesis,according to the basic requirements of Chinese ink drawing from artists,an ink painting has been generated by maximumly abstracting the essential characteristics of the tree based on 3D model,which forms the similar effect with the real world ink painting.In this thesis,we focused on studying the extraction and processing of contour lines,drawn method of stroke.The following work is mainly completed.(1)The processing of contour line of the model has been implemented.This study considered branches with certain thicknesses.The tree visual contours have been obtained by combining geometric and image-based methods.According to the sign of the dot product of the normal of the smooth surface with the view vector at every mesh vertex,the possible locations of the contour points have been determined.Then,we used Sobel algorithm to detect model depth map and normal graph.By setting the threshold at the image level,we connected the contour segment and to determine the stroke path.We used two dimensional cellular automata to simulate brush strokes with ink style.Finally,we drew contour lines along the stroke path,and got the effect of the artistic style of ink painting.(2)The surface model of the tree with artistic style has been drawn.Firstly,we set the ink style strokes texture patterns.Secondly,referenced the depth map,normal map and curvature map of the model,we used the method of procedural texture to simulate the effect of “TS’UN”.We set the tone color table by referring to the artist tone concept.Thirdly,the model was rendered with the tone-based shading method,and was combined with the color of the model.Finally,it showed that the surface of the model has artistic style.