本文選題：樹 + 動態(tài)參數(shù)　； 參考：《西北農(nóng)林科技大學(xué)》2017年碩士論文

【摘要】：真實(shí)感樹動畫對于增加游戲感染力與沉浸感有重要意義。近幾年,為提高樹動畫模擬的真實(shí)感,基于數(shù)據(jù)驅(qū)動的樹動畫模擬方法成為研究熱點(diǎn),而當(dāng)前基于數(shù)據(jù)驅(qū)動的方法存在數(shù)據(jù)獲取設(shè)備昂貴、過程復(fù)雜,樹模型與真實(shí)模型差距較大、模擬樹木運(yùn)動形式有限等問題。針對上述問題,本文采用廉價的Kinect體感設(shè)備,研究基于運(yùn)動視頻和深度數(shù)據(jù)的樹木動態(tài)參數(shù)提取方法和基于點(diǎn)云的樹三維模型構(gòu)建方法,然后將樹動態(tài)參數(shù)與真實(shí)感樹模型輸入到樹動力學(xué)模型,基于模態(tài)分析構(gòu)建動畫模擬系統(tǒng)實(shí)現(xiàn)數(shù)據(jù)驅(qū)動的真實(shí)感樹運(yùn)動模擬。論文主要研究內(nèi)容和結(jié)論如下:(1)利用Kinect V2搭建數(shù)據(jù)實(shí)時采集的試驗(yàn)平臺。通過PC工作站控制架設(shè)于三角支架上的Kinect設(shè)備,同步采集具有標(biāo)記點(diǎn)的樹枝干運(yùn)動視頻流和深度信息流,并采取先寫內(nèi)存、后寫磁盤的存儲策略保存采集的運(yùn)動數(shù)據(jù),以滿足高幀率連續(xù)運(yùn)動數(shù)據(jù)的需求。試驗(yàn)表明,在陽光條件較弱的室外,試驗(yàn)平臺獲取的運(yùn)動視頻流和對應(yīng)的深度信息流的幀率可達(dá)30fps(frames per second),采集的運(yùn)動數(shù)據(jù)滿足后續(xù)研究的需求。(2)針對樹木真實(shí)動態(tài)參數(shù)獲取設(shè)備昂貴、過程復(fù)雜的問題,提出基于局部相對偏轉(zhuǎn)角度量準(zhǔn)則的樹枝干振動頻率與阻尼比獲取方法。該方法通過跟蹤樹枝干顏色特征標(biāo)記,提取各樹枝標(biāo)記點(diǎn)運(yùn)動的二維軌跡;依據(jù)跟蹤結(jié)果構(gòu)建二維樹骨架運(yùn)動模型,并計算子樹枝相對于父樹枝的局部偏轉(zhuǎn)角,通過快速傅里葉變換將時域振動信號變換到頻域,頻域信號的一階振動波峰對應(yīng)的頻率即為擬獲取的樹枝振動頻率;利用阻尼比與一階振動頻率振幅衰減的關(guān)系,采用半波法計算出阻尼比。結(jié)果表明,供試樹木的振動頻率分別為2.4Hz和2.0Hz,樹的振動頻率為樹的固有特征,不隨外力的改變而改變;而樹在運(yùn)動過程中受到的阻尼與外力大小、樹的分支結(jié)構(gòu)有明顯的關(guān)系。(3)為解決數(shù)據(jù)驅(qū)動樹動畫的真實(shí)樹模型構(gòu)建問題,基于空間殖民算法提取樹骨架,并提出樹層次結(jié)構(gòu)模型構(gòu)建及曲率精簡骨架的方法�？臻g殖民算法通過調(diào)整影響半徑、刪除閾值、骨架點(diǎn)距離和生長角度4個參數(shù)迭代生成樹骨架;在設(shè)計樹骨架、樹枝干數(shù)據(jù)結(jié)構(gòu)的基礎(chǔ)上,依據(jù)樹骨架點(diǎn)的關(guān)系構(gòu)建樹枝模型與樹層次結(jié)構(gòu)模型;為保留樹枝彎曲特性,利用相鄰骨架點(diǎn)曲率對骨架進(jìn)行分類與精簡;基于管道模型估算樹枝干粗度,通過廣義圓柱體渲染最終的樹幾何模型。重建結(jié)果表明,基于樹點(diǎn)云重構(gòu)的樹三維模型與原點(diǎn)云吻合度較高,樹形態(tài)結(jié)構(gòu)自然,且樹冠細(xì)枝結(jié)構(gòu)突出,符合真實(shí)樹特征。(4)為實(shí)現(xiàn)真實(shí)感樹木運(yùn)動模擬,基于提取的樹運(yùn)動動態(tài)參數(shù)、真實(shí)點(diǎn)云重建的樹模型,用簡易模態(tài)法實(shí)現(xiàn)了基于數(shù)據(jù)驅(qū)動的樹動畫模擬。通過fBm噪聲模型構(gòu)建樹運(yùn)動風(fēng)速場,并基于空氣動力學(xué)模型計算風(fēng)力;采用簡化的彎曲梁模型表示彎曲樹枝干結(jié)構(gòu),振動頻率和阻尼比作為時域運(yùn)動方程的參數(shù)引入各占優(yōu)振動模態(tài)的運(yùn)動方程,通過求解簡易模態(tài)分析方法的時域方程和空域方程實(shí)現(xiàn)樹枝形變彎曲角度計算;整合彎曲樹枝各節(jié)段的運(yùn)動得到彎曲樹枝整體運(yùn)動,整合各彎曲樹枝運(yùn)動得到樹整體運(yùn)動。模擬試驗(yàn)結(jié)果表明,本文實(shí)現(xiàn)的樹動畫模擬系統(tǒng)交互式操作風(fēng)向、風(fēng)速的同時,可渲染幀率約為25~30fps的流暢樹運(yùn)動動畫,效率較高;樹的運(yùn)動形態(tài)隨風(fēng)力與風(fēng)向的改變而變化,中間層次長樹枝彈性形變明顯,樹冠細(xì)枝隨父樹枝運(yùn)動而運(yùn)動,模擬的樹運(yùn)動符合冬季無葉玉蘭樹的特征;此外,對均勻點(diǎn)云及地面激光點(diǎn)云樹模型的運(yùn)動模擬表明本文模擬系統(tǒng)具有普適性。
[Abstract]:Realistic tree animation is of great significance to increase the appeal and immersion of the game. In recent years, in order to improve the realistic sense of tree animation simulation, data driven tree animation simulation method has become a hot topic, and the current data driven method is expensive, the process is complex and the gap between the tree model and the real model is large. In view of the above problems, this paper uses cheap Kinect somatosensory equipment to study the method of tree dynamic parameters extraction based on motion video and depth data and the building method of tree 3D model based on point cloud. Then the tree dynamic parameters and real real tree model are input into the tree dynamics model, and the model is based on the model. The main research contents and conclusions of this paper are as follows: (1) build a test platform for real-time data acquisition by using Kinect V2. Control the Kinect equipment erected on the triangular scaffold by PC workstation, and synchronize the video stream of branch trunk motion video with marked point. The experiment shows that the frame rate of the motion video stream and the corresponding depth information stream can reach 30fps (frames per second), and the collection is carried out. The dynamic data meet the needs of subsequent research. (2) a method of obtaining the vibration frequency and damping ratio of branches based on the local relative deflection angle criterion is proposed to obtain the expensive and complicated process of the tree real dynamic parameters. This method is used to track the two dimensional trajectories of the movement of the branches of the branches by tracking the color characteristics of the branches of the branches. Based on the tracking results, the two-dimensional tree skeleton motion model is constructed, and the local deflection angle of the sub branches relative to the parent branch is calculated. The time domain vibration signals are converted to the frequency domain by the fast Fourier transform. The frequency of the corresponding vibration peaks of the first order vibration peaks of the frequency domain signals is the frequency of the proposed branch vibration, and the damping ratio and the first order vibration frequency amplitude are used. The damping ratio is calculated by the semi wave method. The results show that the vibration frequency of the tested trees is 2.4Hz and 2.0Hz respectively. The vibration frequency of the tree is the inherent characteristic of the tree and does not change with the change of the external force; and the damping and external force of the tree are obviously related to the branch structure of the tree in the process of movement. (3) the data drive is solved. The real tree model of dynamic tree animation is built. Based on the spatial colony algorithm, the tree skeleton is extracted and the tree hierarchy model is constructed and the curvature simplification method is proposed. The spatial colony algorithm generates the tree skeleton by 4 parameters, which are adjusting the influence radius, removing the threshold, the distance of the skeleton point and the growth angle, and designing the tree skeleton and the trunk number. Based on the structure, the branch model and the tree hierarchy model are constructed according to the relationship between the tree skeleton points. In order to preserve the bending characteristics of the branches, the curvature of the adjacent skeleton points is used to classify and simplify the skeleton, and the trunk roughness is estimated based on the pipeline model and the final tree geometry model is rendered through the generalized cylinder. The reconstruction results show that the tree is based on the tree. The three dimensional model of point cloud reconstruction is higher than the original point cloud kiss, the tree structure is natural, and the tree crown fine branch structure is prominent. (4) in order to realize the realistic tree motion simulation, the tree model based on the dynamic parameters of the extracted tree motion, the real point cloud reconstruction model, and the simple modal method to realize the tree animation model based on data driven. The wind velocity field of tree motion is constructed by the fBm noise model, and the wind is calculated based on the aerodynamics model. The simplified bending beam model is used to express the bending branch structure. The vibration frequency and damping ratio are used as the parameters of the time domain motion equation to introduce the motion square of each dominant vibration mode, and the time domain formula is solved by solving the simple modal analysis method. The bending angle of the branch is calculated by the equation of the range and the space domain, and the motion of the curved branch is obtained by integrating the motion of the flexural branches, and the whole motion of the tree is obtained by the integration of the curved branches. The simulation results show that the tree animation simulation system is interactive with the wind direction and the wind speed is at the same time, the rendering frame rate is about 25~30fps The fluency tree motion animation has high efficiency, the tree movement pattern changes with the change of wind force and wind direction, the elastic deformation of the long branch in the middle level is obvious, the tree crown fine branch moves with the parent branch, and the simulated tree motion is in accordance with the characteristics of no Ye Yulan tree in winter. In addition, the motion simulation table of uniform point cloud and ground laser point cloud tree model is also made. The simulation system of this article is universally applicable.
【學(xué)位授予單位】：西北農(nóng)林科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TP391.41

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