本文選題：Android　切入點：三維點云重建　出處：《西北農林科技大學》2017年碩士論文　論文類型：學位論文

【摘要】：作物三維模型渲染是農業(yè)信息化領域的研究熱點。目前,作物的三維模型渲染多數(shù)是基于PC端。但在智能設備迅速發(fā)展的今天,人們希望能夠在移動端有良好的視覺體驗,因此本文通過對一些渲染算法移植,從而實現(xiàn)這一目標。其中的關鍵問題是如何將這些算法進行改進使其適應移動端低帶寬、低功耗的需求。本研究以作物三維模型為研究對象,在詳細分析其原理、實現(xiàn)過程后,基于Android平臺結合OpenGL ES圖形庫實現(xiàn)了作物三維模型的渲染。主要內容如下:(1)實現(xiàn)了作物三維點云的重建算法,獲取了三維模型。針對本設計輸入的點云是精簡去噪的點云,且其來自一個掃描設備或多個掃描設備的特點,選取適合該三維點云的重建算法—貪婪投影算法對玉蘭樹和玉米植株等多種作物進行重建,獲得了很好的重建效果。通過與泊松重建算法對比,針對植物等散亂葉片的點云數(shù)據(jù),雖然貪婪投影算法效率低于泊松重建算法約20.61%,但是能夠體現(xiàn)植物的拓撲結構,而泊松重建雖然時間效率高,但出現(xiàn)冗余面。(2)實現(xiàn)了移動端三維模型的顯示。針對三維模型如何在移動端顯示的問題,本文采用了應用廣泛的3D標準文件類型—STL文件保存獲取到的三維模型。使用OpenGL ES在Android Studio上實現(xiàn)三維模型的獲取,實驗結果表明該讀取方式可以對STL文件讀取并顯示,且顯示位置自適應于手機屏幕。(3)實現(xiàn)了以光照為核心的移動端三維模型的渲染。針對模型不夠真實,視覺效果不佳的問題,本文對模型進行了局部光照處理和全局光照處理。局部光照處理采用Phong氏光照模型,很好的模擬了高光效果;全局光照處理采用光線跟蹤算法,很好的模擬了光照下的陰影效果。在網(wǎng)格面達到85436時,移動端依然可以實現(xiàn)渲染,渲染時間為36.24分。本文還對該方法進行了功能性測試和普適性測試。實驗基于斯坦福Bunny密集點云數(shù)據(jù)對該方法進行功能性測試,選取八組數(shù)量不同的點云數(shù)據(jù)進行渲染對比,測試用例表明模型表面的光滑程度會對渲染結果造成影響,當點云數(shù)量少于3305時,高光面有明顯的缺損;選取不同類型的三維模型進行普適性測試,測試用例表明該方法可以實現(xiàn)多種模型的渲染。通過以上兩方面的測試,結果表明該方法實現(xiàn)了預期的功能,且能夠廣泛使用。
[Abstract]:Crop 3D model rendering is a hot topic in the field of agricultural informatization. At present, most of crop 3D model rendering is based on PC. However, with the rapid development of intelligent devices, people hope to have a good visual experience on mobile side. The key problem in this paper is how to adapt these algorithms to the low bandwidth on the mobile side. In this study, the three dimensional model of crop is taken as the research object, after the detailed analysis of its principle, the realization process, Based on Android platform and OpenGL es graphics library, the rendering of crop 3D model is realized. The main contents are as follows: 1) the reconstruction algorithm of crop 3D point cloud is realized, and the 3D model is obtained. The point cloud input in this design is a reduced denoising point cloud. Based on the characteristics of one or more scanning devices, the greedy projection algorithm, which is suitable for the 3D point cloud reconstruction, is selected to reconstruct magnolia and maize plants. Compared with Poisson's reconstruction algorithm, the greedy projection algorithm is less efficient than Poisson's reconstruction algorithm, but it can reflect the topological structure of plants, although the greedy projection algorithm is less efficient than Poisson's reconstruction algorithm. Poisson reconstruction has high time efficiency, but redundant surface. 2) realize the display of 3D model of mobile terminal. In view of the problem of how to display 3D model on mobile side, This paper adopts 3D standard file type -STL file which is widely used to save the acquired 3D model. We use OpenGL es to obtain 3D model on Android Studio. The experimental results show that the method can read and display the STL file. And the display position adapts to the mobile phone screen. 3) it realizes the rendering of the 3D model of the mobile end with illumination as the core. Aiming at the problem that the model is not real enough and the visual effect is not good, In this paper, the local illumination processing and the global illumination processing are carried out. The Phong illumination model is used in the local illumination processing, and the highlight effect is well simulated, and the global illumination processing is based on the ray-tracking algorithm. Very good simulation of the shadow effect under light. When the mesh surface reaches 85436, the mobile side can still render, The rendering time is 36.24 points. This paper also carries on the functional test and the universality test to this method. The experiment carries on the function test based on the Stanford Bunny dense point cloud data, selects eight groups of points cloud data to render the contrast, Test cases show that the smoothness of the surface of the model will affect the rendering results. When the number of point clouds is less than 3305, the high light surface has obvious defects. The test cases show that the method can be used to render multiple models. The results show that the proposed method achieves the expected function and can be widely used.
【學位授予單位】：西北農林科技大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TP391.41;TP316

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