基于球面全景圖的三維實(shí)景制作

1、基于球面全景圖的三維實(shí)景制作摘要：三維實(shí)景也叫虛擬現(xiàn)實(shí)（Virtual Reality）全景，是基于序列圖片的數(shù)字三維全景技術(shù)。它使用專門的魚眼鏡頭拍攝序列真實(shí)圖片，經(jīng)過拼接融合生成球面全景圖。本文結(jié)合三維全景制作相關(guān)流程，探討了與之相關(guān)的理論與關(guān)鍵技術(shù)，形成了一整套全景影像獲取、拼接、發(fā)布技術(shù)流程,最后與*大學(xué)檔案館的數(shù)字化建設(shè)相結(jié)合，介紹了三維全景系統(tǒng)的關(guān)鍵制作步驟。關(guān)鍵詞：虛擬現(xiàn)實(shí) 圖像拼接 圖像融合 球面全景圖Abstract: Three-dimensional virtual reality is also called the Virtual Reality, its a dig

2、ital three-dimensional panoramic technology based on sequence images. It uses specialized fish-eye lens to shoot sequences of real pictures, through the fusion splicing generates a spherical panorama. In this paper, based on three-dimensional panoramic production related processes discussed the asso

3、ciated theories and key technologies, formed a complete set of panoramic imaging gets, splicing, publication technology process, finally combined with the digital construction of * University Archives,introduced the keysteps in the production ofthree-dimensionalpanorama system.Keywords: Virtual real

4、ity Image stitching Image matching Spherical Panoramic Image1 引言廣義上的全景就是視角范圍超過人的正常視角的圖像，本文我們說的全景特指水平視角360，垂直視角180的圖像。360全景最大的三個(gè)特點(diǎn)是： 1、全：全方位，用戶可觀看左右 360，上下180球型范圍內(nèi)的所有景致； 2、景：實(shí)景，在現(xiàn)場采集的一系列照片基礎(chǔ)上經(jīng)過拼接合成得到的最大限度的保留了場景真實(shí)性的全景照片； 3、360：360環(huán)視的效果，雖然照片都是平面的，但是通過軟件處理之后得到的360實(shí)景，卻能給人以三維立體的空間感覺，使觀者猶如身在其中。 由于它給人們帶來全新的

5、真實(shí)現(xiàn)場感和交互式的感受，故可廣泛應(yīng)用于三維電子商務(wù)，如在線的房地產(chǎn)樓盤展示、虛擬旅游、虛擬教育、醫(yī)療、航空等領(lǐng)域。在地質(zhì)勘測、軍事偵察、醫(yī)學(xué)微創(chuàng)手術(shù)、航空航天以及視頻會議等多個(gè)領(lǐng)域都發(fā)揮著重要作用。1 Introduction Panorama in a broad sense is the image perspective beyond the normal , panoramic of this article we say especially a horizontal angle of 360 , 180 vertical perspective image. Three larg

6、est features of the 360 panorama are:1. Entire: Omni-directional, users can watch around 360 , 180 spherical range up and down all of the landscape;2. Scenery: Outdoor scene, panorama basedona series of photoscollectedand throughthe mosaicsynthesishas retainedthe authenticity of the scene;3. 360: Th

7、e effect of 360 look around, although the pictures are flat, but the 360 virtual when processed through the software will bring a person with three-dimensional feeling, just like the Viewer is in it.2 三維全景關(guān)鍵技術(shù)2 The key technology of three-dimensional panorama2.1 The general process ofpanorama genera

8、tion 2.1 全景圖生成一般流程本文系統(tǒng)在基于IBR方法基礎(chǔ)上，先利用數(shù)碼相機(jī)+魚眼鏡頭采集場景序列圖片，然后把多幅全景圖投影到合適的空間模型，本文采用的是球面投影模型，再把拼接處理過的全景圖組織成虛擬的全景空間，用戶通過場景中導(dǎo)航圖標(biāo)可以在這個(gè)虛擬空間進(jìn)行前進(jìn)、后退、轉(zhuǎn)彎、切換場景等漫游；每個(gè)場景都可以進(jìn)行360環(huán)視、變焦瀏覽等操作。綜上所述，基于全景圖技術(shù)的虛擬場景生成過程可以用圖2.1表示。The system in this paper isbased on the IBR method,and use thedigital camera withfisheye lensacqui

9、sitionsequence of scenes, Then put a number of images projected onto the appropriate space model of panoramic image, we use the spherical projection model this paper, Then treated stitching panorama organized into virtual panoramic space, Users navigate through the scenario icon can be forward, back

10、ward, turn, switch scenes roaming in this virtual space; Each scene can be 360 degrees around, zoom browsing operations etc. In summary, virtual scene generation process based on panorama technology can be represented by Figure 2.1確定圖像的生成方式計(jì)算機(jī)繪制普通相機(jī)全景相機(jī)投影變換拼接融合生成全景圖鏈接全景圖瀏覽虛擬場景圖2.1 全景圖生成流程圖Figure 2.1

11、 Flowchart of panoramas generate 2.2 全景圖像采集全景圖像的拍攝要求360無死角的視角角度，所以對全景設(shè)備有著較高的要求，總體來說在圖像的采集過程中要求有以下幾點(diǎn)1：1、拍攝角度要恰當(dāng)，相機(jī)應(yīng)大致位于一個(gè)場景的中心位置。2、拍攝水平角度圖像時(shí)，要盡可能的避免平轉(zhuǎn)數(shù)碼相機(jī)時(shí)鏡頭的偏斜和俯仰，盡量保持相機(jī)水平旋轉(zhuǎn)。3、相機(jī)要盡可能的繞光心旋轉(zhuǎn)。偏離光心引入的誤差會導(dǎo)致插值圖像時(shí)的重影和定位困難。 4、拍攝時(shí)光圈和焦距要固定不變。不同的光圈會使拍攝的不同方向的照片亮度、對比度和色彩差異較大。5、同一場景的序列圖像必須有重疊部分，一般重疊區(qū)域約為30%-50%之間，

12、這樣拼接圖像的時(shí)候才有足夠的匹配點(diǎn)。 6、同一場景的采集時(shí)間要盡快，間隔不要太久，以免風(fēng)云變色，帶來外界環(huán)境變化，影響拼接效果。7、在拍攝時(shí)，場景中盡量不要出現(xiàn)移動(dòng)的物體。2.2 Panoramic image acquisitionPanoramashooting requires360 no dead angle ofview,therefore has a higher requestto thepanoramic equipment, In generalthe image acquisition processrequirementsare as follows1:The camer

13、a angle to be appropriate, the camera should be roughly located in the center of a scene.When shootingHorizontal angle image,to avoid as much as possibledeviationand pitch when the digital camera pan,and try tokeep the camerarotation.Rotation around the optical center of the camera as much as possib

14、le. Errorintroduced by deviating from the optical center will cause interpolation image ghosting and difficult to locate.When shooting, aperture and focal length to be fixed. Different aperture would make photos of the different direction of brightness, contrast and color quite different.Sequenceima

15、ges of the same scenemusthave overlapping parts. General overlap area approximately 30% to 50%, so when stitching images have enough matching points.Acquisition time of the same scene as soon as possible, not too long intervals, in order to avoid the situation discoloration, bringing the external en

16、vironment changes that affect splicing effect.In filming, try not to appear moving object in the scene.球面全景空間的視點(diǎn)空間對應(yīng)單一視點(diǎn)處的球面范圍，要獲取該范圍內(nèi)的實(shí)景圖，需要固定照相機(jī)或攝像機(jī)的位置，平轉(zhuǎn)照相機(jī)或攝像機(jī)，每旋轉(zhuǎn)一定的角度，拍攝一張照片2，完成水平360景象的拍攝后，需要將相機(jī)從最初的水平位置向上翻轉(zhuǎn)90，使鏡頭朝上拍一張此場景天空的照片。但是由于拍攝天空時(shí)的鏡頭比拍攝水平方向時(shí)的鏡頭要高，所以要把相機(jī)往下調(diào)一點(diǎn)。完成對天空的拍攝后，再將三腳架向后移動(dòng)一定距離，把相機(jī)向下旋

17、轉(zhuǎn)到最大角度（大約75左右）拍一張地的照片，這樣就完成了一個(gè)場景的360拍攝。拍攝實(shí)景圖像使用的器材包括三腳架、水平儀和數(shù)碼相機(jī)等。如圖2.2所示。View space in spherical panoramic space corresponding to the singleview pointof Sphericalrange,to get thereal mapin the range,you need fixedcamera orcamera position, swingthe camera, rotatesa certain angle,take a photo 2, Comp

18、lete thelevel360 degreesceneshooting,the camera needs tobeturned up 90 degreesfrom the originalhorizontal position,make the lens upward to shoot sky of this scene. However, due to the lens when shooting the sky higher than shooting horizontal, so put the cameradowna bit. After completing the shoot t

19、o the sky, and then moving the tripod backward at a distance，put the camera down to its maximum angle (about 75 or so) to take a photo of earth, this completesa scene of360 shooting. Shooting real images using equipment includes tripods, levels and digital cameras, etc. As shown in Figure 2.2.圖2.2 拍

20、攝實(shí)景圖像裝置圖Figure 2.2 Diagram of apparatus to taken real images 2.3 球面投影球面全景圖的投影是將魚眼照片上的點(diǎn)映射到球面模型上(如圖2.3所示)，所有的投影線都是與球面垂直的，所以沒有如傳統(tǒng)平面圖像中的光軸3。因此，只要在球面視圖中可見，空間中的每個(gè)點(diǎn)都能在球面投影中展示出來。2.3 Spherical projection Spherical panorama projection is to map the points on the fisheye photos to spherical model (as shown in

21、figure 2.3), All projection lines are perpendicular to the sphere s, so there is no optical axis like tradition plane image3. Therefore, as long as visible in the spherical view, each point in the space can be displayed in the stereographic projection.圖2.3 球面變換示意Figure 2.3 spherical transform indica

22、tion如圖2.3所示，相機(jī)位于半徑為 f 的球體中心，相機(jī)的拍攝方向即投影的方向由極角 (相機(jī)視線與相機(jī)坐標(biāo)系Z 軸的夾角)和方位角 (相機(jī)視線在相機(jī)坐標(biāo)系中 XY 平面內(nèi)的投影與 X 軸的夾角)決定。在球面投影中，相機(jī)坐標(biāo)系與球面坐標(biāo)系是一樣的。假設(shè) P 在世界坐標(biāo)系中的坐標(biāo)為： (1)P 在球面上的投影點(diǎn) p 的球面坐標(biāo)可以表示為: (2)推導(dǎo)出: (3)這里 。由此，可以通過該公式算出照片上任意點(diǎn) P 在投影球面的對應(yīng)點(diǎn) p 的坐標(biāo)。2.3.1 而我等均為地哦我去山東龍口就愛死爹我As shown in figure 2.3, the camera is located in the

23、center of a sphere with a radius of f, Camera shooting direction that is projection direction is determined by the polar Angle(The angle between the camera line of sight and Camera coordinate system z axis)and azimuth Angle(The angle between the camera line of sight in the camera coordinate system X

24、Y plane and the X axis). In spherical projection, the camera coordinate system and the spherical coordinate system is the same. Assume that the coordinates of P in the world coordinate system is: (1)The spherical coordinates of the projection point p of P can be expressed as: (2)Can be deduced: (3)H

25、ere.Thus, the coordinates of anypoint P correspondsP in projectionsurface Can be calculated by the formula.2.4全景圖拼接簡單地說，圖像拼接就是把采集到的一些有相互重疊區(qū)域的圖像序列變成一副無縫的360全景圖。對于由于經(jīng)濟(jì)原因而采用非全視角相機(jī)拍攝的圖片來說，圖像的拼接是構(gòu)建360虛擬全景空間的一個(gè)重要步驟，拼接質(zhì)量的好壞，決定了能否給用戶一個(gè)逼真的、真實(shí)的瀏覽效果。一般來說，圖像拼接的誤差應(yīng)小于一個(gè)像素。由于拍攝到的相鄰的圖片之間存在一定區(qū)域的重疊，如圖2.4所示，可以以此為拼接方法的

26、入手點(diǎn)，用拼接工具識別出相鄰圖片的重疊區(qū)域，從而達(dá)到生成全景圖的目的。為了達(dá)到讓人滿意的拼接效果，重疊區(qū)域大小要適當(dāng)，對于圖像特征明顯的圖片，重疊區(qū)域可以小一些，反之，就要大一些。一般情況下，相鄰兩幅圖像的重疊部分應(yīng)該在30%50%之間。2.4 Panorama stitching In brief, image stitching is to put sequence of overlapping images into a seamless 360panoramas. Images which for economic reason that use non-full-view camer

27、a shoot, image stitching is an important step to build 360 virtual panorama space, stitchingquality,decides whetherto give users a realistic and authentic view. In general, image stitching error should be less than one pixel. Because of there is a certain area of overlap between adjacent images, as

28、shown in figure 2.4, we can take this as a starting point of stitching method, with splicing tool to identify the overlap of adjacent images, so as to achieve the purpose of generating panorama. In order to achieve satisfactory splicing effect, overlapping region size should be appropriate, for Imag

29、es which have significant feature, overlapping area can be smaller, conversely, will greatly. In general, the overlap between two images should be between 30% - 50%.圖2.4 全景圖拼接示意圖2.5圖像融合對圖像進(jìn)行匹配之后，只是完成了對圖像的定位。如果這時(shí)只根據(jù)拼接算法求得的兩幅圖像上下和水平方向的平移參數(shù)將兩幅圖簡單的疊加起來，由于相鄰圖像之間存在的亮度差異和拍攝時(shí)三腳架旋轉(zhuǎn)對拍攝圖像帶來的影響等原因，就會出現(xiàn)合成的圖像有清晰的

30、邊界，拼接痕跡明顯等讓我們不能接受的現(xiàn)象。而圖像融合4就是在圖像匹配之后對圖像像素值進(jìn)行處理，目的是在保證圖像的質(zhì)量不發(fā)生改變的前提下消除圖像拼接后出現(xiàn)的拼接痕跡。2.5 Image Fusion After the image matching, just completed the positioning of the image. At this time, if you simply overlay two images together only according to vertical and horizontal translational parametersobtained

31、by stitching algorithm, Due to brightness differences exist between adjacent images and effects of rotation on a tripod when shooting images and other reasons, there will bethe synthetic images haveclear boundaries,obvious splicing traces, which we obviously cannot accept phenomenon. Image fusion is

32、 to processing image pixels after image matching, objective is to removing splicing traces under the premise of guarantee the quality of the image does not change. 3 應(yīng)用實(shí)例本節(jié)將結(jié)合相關(guān)理論和算法實(shí)現(xiàn)一個(gè)全景圖漫游系統(tǒng)，本系統(tǒng)是大學(xué)校史館的三維全景漫游系統(tǒng)。為廣大校友提供了一個(gè)足不出戶便可身臨其境的瀏覽母校歷史的平臺。系統(tǒng)中對關(guān)鍵圖片和文字配有多邊形熱區(qū)，用戶通過點(diǎn)擊想要細(xì)致閱讀查看的區(qū)域，即可彈出相應(yīng)的放大圖片或相關(guān)視頻文件。

33、不僅方便了用戶查看，更增加了系統(tǒng)的生動(dòng)性和真實(shí)感。系統(tǒng)主界面如圖所示：3 Application examples This section will combine related theories and algorithms to achieve a panorama roaming system, this system is a three-dimensional panoramic roaming system of xx university History Museum. For our alumni provides a platform for immersive browsing alma mater history without leaving home. In this system, key image and text are equipped with polygon hot spot, users by clicking on the area which he want careful reading, the corresponding enlarge images or related video files will pop up. Not only convenient for users to view,