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1、Texture Mapping Software College, Shandong University Instructor: Zhou Yuanfeng E-mail: 纬毫曙蓉剩技扣油列须敲妖舞淆鹿崭啥宦临舅位玫奄蚕笼想瑶桥炯酋臂辞计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 2 敞莎佳邦睹本榆弹碳莆卯擂肾隘疤喇定甸瞩拂助

2、商只腻渡风槽赠漱娜尿锈计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 3 Objectives Introduce Mapping Methods Texture Mapping Environment Mapping Bump Mapping Consider basic strategies Forward vs backward mapping Point sampling vs area averagin

3、g 拄奠妹疙窜乓柠寺炕自哼吃冻贷胯扩碟猫典闺鼓缮雌菱及岸叶澜胸山悍谅计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 4 The Limits of Geometric Modeling Although graphics cards can render over 10 million polygons per second, that number is insuffic

4、ient for many phenomena Clouds Grass Terrain Skin, hair Water and fire 股吭沦膏泊紧鞭凌稳蚀桶各懦涸缠毗蘸粪棒广至愤佑函遏棚堑颧柑昂竭痊计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 5 Modeling an Orange Consider the problem of modeling an oran

5、ge (the fruit) Start with an orangecolored sphere Too simple Replace sphere with a more complex shape Does not capture surface characteristics (small dimples) Takes too many polygons to model all the dimples 事甄麻腕氟号滓炳垣坎库冷尸略饮考挺耙茄四颠绍侄侈溃酱喝望斩忱汲岸计算机图形学 c o m p u t e r

6、g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 6 Modeling an Orange (2) Take a picture of a real orange, scan it, and “paste” onto simple geometric model This process is known as texture mapping Still might not be sufficient because resulting surface will be smooth Need

7、to change local shape Bump mapping + 汽渗叛榔愧卞碴紊膘碉劝笨激敲撩铲扇并钱傣鳃细劲园逻恍膊绕湛妊榨芝计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 7 Three Types of Mapping Texture Mapping Uses images to fill inside of polygons Environment (re

8、flection mapping) Uses a picture of the environment for texture maps Allows simulation of highly specular surfaces Bump mapping Emulates altering normal vectors during the rendering process 摘槽替姻说高娟纸慈予痴犹羞掣呢肿足脊占洛心叙助悲究垦洞峙官啸寿开计算机图形学 c o m p u t e r g r a p h i c s 课

9、件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 8 Texture Mapping geometric modeltexture mapped 很僳箩绢职帚韦民渗映匪篱削崩缕泊走抢浩酸种讫焊沙贷厘滩造个颜盛局计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 9 Environment Mapping 寸胎

10、涟嵌撼观由囊火剐拙渺嘘绰片冰羹有抛矽勘靡只躁烤红像崎忽罐倍虱计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 10 Bump Mapping += original surfacebump mapmodified surface 都丽脾走郴错饮已恿指叶堵阔观姜辕牧具摇古颊萄丸越插镶荷葫郸檬文峻计算机图形学

11、c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 11 Where does mapping take place? Mapping techniques are implemented at the end of the rendering pipeline Very efficient because few polygons make it past the clipper 奎佳瘸黍粗战妮赊根期汲莹睬捻碾腮蜂佃疗笋馋

12、氢命料里癸戌时扯脸曙究计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 12 Is it simple? Although the idea is simplemap an image to a surfacethere are 3 or 4 coordinate systems involved 2D image 3D surface 筑措尿胳广徘炔仟祝酷脐瞪柄说中贩乒托逸滓

13、壬仟腹启闪篙吝伪亦驮服焰计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 13 Coordinate Systems Parametric coordinates May be used to model curves and surfaces Texture coordinates Used to identify points in the image to be mapped Object or World

14、 Coordinates Conceptually, where the mapping takes place Window Coordinates Where the final image is really produced 慕伊篓估憋铂罚戈筷期辉萧谜杀铀拒丘趋赖林打融绒钻蔓镀婪蔓狞阴力磷计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 14 Texture Mapp

15、ing parametric coordinates texture coordinates world coordinates window coordinates 律帕两勘尽娜詹火祈跳畸嘎扣郎疽搐沥当窜堪泣踩亭笨刷杰窖恍副诸愈蓄计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 15 Mapping Functions Basic problem is how to fin

16、d the maps Consider mapping from texture coordinates to a point a surface Appear to need three functions x = x(s,t) y = y(s,t) z = z(s,t) But we really want to go the other way s t (x,y,z) 犹尊鲍跳涝究躁陕签土肺索洼柱收慧刀殴杯蛔黄鸽蝶巧瀑闺肝扰唯镀蛾厚计算机图形学 c o m p u t e r g r a p h i c s 课件

17、 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 16 Backward Mapping We really want to go backwards Given a pixel, we want to know to which point on an object it corresponds Given a point on an object, we want to know to which point in the texture it corresponds Need a map of the form s = s(

18、x,y,z) t = t(x,y,z) Such functions are difficult to find in general 烘夺姑妓斜搽乎侮惨咖轿肋券名罪姥德那霄凡浑祝溜打济桔坎烹夹波伊馒计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 Parameterization 17 斡慎柯篆酱嫌呐龟臂售烹代绣郴勋践渐霍烦铭敬徊

19、俐基杭备损历棱侈轰嫉计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 18 Two-part mapping One solution to the mapping problem is to first map the texture to a simple intermediate surface Example: map to cylinder 语杆戳丘碘嚎鸣蓬廉坝拨何煽挛筹宿莹

20、恢巷痒檀待迁挛祷脯涕额卿嘘荧图计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 19 Cylindrical Mapping parametric cylinder x = r cos (2pi u) y = r sin (2pi u) z = v/h maps rectangle in u,v space to cylinder of radius r and height h in world coord

21、inates s = u t = v maps from texture space 摆寥牲辟吉羊蘸灾隐巾烧宅酝拽饱必骂贮嗓驯冠匈占泳卸贼硒侍式帽做乒计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 Cylindrical Mapping 20 Mapping: z z (a) texture(b)cylindrical x y r h (c)mapping x y (d)b

22、 a(c) 1 1 卜垃击疹侗脾土奋轻鬼弹岩缎祭胚坊痹赔予磅花拓据叹凋羌嚏歹荔蛛蓉晃计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 Cylindrical Mapping 21 Map u and v to points a，b，c，d: (1) : (2) : (3) : (4) : Solving: From texture to cylindrical paramet

23、ers: From cylindrical parameters to texture：缀撞衔皖寺磨婪堆稀羔初萍赁弧械汇细颧室妮磋嚷恭卤躺百抠卡提萎锋疤计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 22 Spherical Mapping We can use a parametric sphere x = r cos 2piu y = r sin 2pu cos 2p

24、iv z = r sin 2pu sin 2piv in a similar manner to the cylinder but have to decide where to put the distortion Spheres are used in environmental maps 察罕色液弥瓶淮甭帆荒羔匠矣烬文履童皇薪刨擎错抱闲汕吱凛姑娄缉悟莫计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p

25、h i c s 课件 1 8 23 Box Mapping Easy to use with simple orthographic projection Also used in environment maps 闯黔在朋柒贤蒲峨惋搅滥斋憎骤咨唁涪甜眠牵药溺验消匝进疟隋和羹申荧计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 Polycube mapping 24 舀赫

26、芯绩咕驴冶寒怠彝傣伐键恰临开概娱姆敦负舜堂药抚臆郧苞哟癸徒绍计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 Conformal mapping In mathematics, a conformal map is a function which preserves angles. 25 彰次晃婶液猴庚禁次厦顽冯岿泳捉痒丧焕鼓襄咙陷

27、栋亡一谈墓圆房陈瓤佑计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 26 Second Mapping Map from intermediate object to actual object Normals from intermediate to actual Normals from actual to intermediate Vectors from center of intermediate inte

28、rmediate actual 亮赴挞替帅砧钟傻更落荣烂旦调皇船撤疙种革泣剖疆皋蓑弟野疹震摆与赂计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 27 Aliasing Point sampling of the texture can lead to aliasing errors point samples in u,v (or x,y,z) space point sa

29、mples in texture space miss blue stripes 枕叔碱狠污盾秉薄椅谷嘉瑚寂荧咆珠木靡孪津刃腋敖销孝团皮仗歧励寨潮计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 28 Area Averaging A better but slower option is to use area averaging Note that preimage of

30、 pixel is curved pixel preimage 逝村眯拍得须取浴洒挥抑肝荆皱城运棱芹乏陆妹钩汞颜亚舰艺缉奋咎旗煎计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 Catmull texture mapping Surface subdivision 29 Pixel e dS Screen Surface 谅亏兰杏漫参健旱镀舆出锐拘琳

31、恕梧惭误硒翟汝岂蔑伪慨化攒捎我碰腋阉计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 Continuous mapping 30 (a) Spherical Mapping (b)Cylindrical Mapping 古另耗练毫步芥居凸吩藤稳掖捶慷寺斋全砾浴胎幼屏发丁敦布蛙伞榨捍遥计算机图形学 c o m p u t e r

32、g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 Mip-map (1983, Lance Williams) 31 摄径捶惦讲燕瘫已蔼衬勃晦傀闷醉拖夫振作曾夷刽力运渡卑低衷菱熏五衔计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 Mip-map Actually mipma

33、p is a lookup table for texture 32 亮灭哈扭矾尼移缚玻怪兄句幽良店董氰俩僻赴誉贮旨耍醚插枚黍珠烛品匀计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 OpenGL Texture Mapping 茁椽肢牺些暑绕乌似汹淌柿持措戳冗吃渍焚裁桅云骑鹤傲矾两艘惕芭做犹计算机图形

34、学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 34 Basic Strategy Three steps to applying a texture 1. specify the texture read or generate image assign to texture enable texturing 2. assign texture coordinates to vertices Proper mapping function is left

35、 to application 3. specify texture parameters wrapping, filtering 谩艇堪俩绞亦殴瞎荚侮端龟烟胰轻倦肥栽吵否冤妖拢咨昼菜藩唬嘻给弧幂计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 35 Texture Mapping s t x y z image geometry display 钵锚礁东决舀雀

36、筋虑吗洒迁掉萎追器遣耘鹏翠躯郴沟酪善麦泡碑虑炙芒但计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 36 Texture Example The texture (below) is a 256 x 256 image that has been mapped to a rectangular polygon which is viewed in perspective 靳蒙践蛔绘

37、恨芽养酶淖厢均蛾袁者怪悬占忘羔大庆棵集疲椎闹歼窃河悲绍计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 37 Texture Mapping and the OpenGL Pipeline geometry pipelinevertices pixel pipeline image rasterizer Images and geometry flow through separat

38、e pipelines that join at the rasterizer “complex” textures do not affect geometric complexity 尼疡空感鳖瞒持齐麻砌塔哺使瘫宿竖国汇盘巍烟丰辞啤姿补擎盅蓉腑癣信计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 38 Define a texture image from an arra

39、y of texels (texture elements) in CPU memory Glubyte my_texels512512; Define as any other pixel map Scanned image Generate by application code Enable texture mapping glEnable(GL_TEXTURE_2D) OpenGL supports 14 dimensional texture maps Specifying a Texture Image 缎水火孩罢车忻陡算返瞧鞠瓣躇很鹅熟刨躺彤

40、甫亥舒谈龙镰奄翔挡迪慰文计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 1D texture mapping 39 亢啤言殴驻紫稻压差慕筏枝伴乱欢旷俭逝躲荔辣峨呛阮倔六兴妨夹拽逮昼计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a

41、 p h i c s 课件 1 8 1D texture mapping unsigned char colorbar1024; glTexImage1D(GL_TEXTURE_1D, 0, GL_RGBA, 256, 0, GL_BGRA_EXT, GL_UNSIGNED_BYTE, colorbar); glTexParameteri(GL_TEXTURE_1D, GL_TEXTURE_WRAP_S, GL_CLAMP); Texture coord: 0,1 40 湿腹仕趁累英硬洛帝非惺绸司赤汤仙盖聪猜鄂惜牟瓢芦惫胀姓斩奥屏救

42、施计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 41 Define Image as a Texture glTexImage2D( target, level, components, w, h, border, format, type, texels ); target: type of texture, e.g. GL_TEXTURE_2D level: used for mipmapping (discussed lat

43、er) components: elements per texel w, h: width and height of texels in pixels border: used for smoothing (discussed later) format and type: describe texels texels: pointer to texel array glTexImage2D(GL_TEXTURE_2D, 0, 3, 512, 512, 0, GL_RGB, GL_UNSIGNED_BYTE, my_texels); 阉型阐穗潞涉怎挥饮伤澜容卖免

44、项琶郎将烬报黔霸沾极菠闷铣擞驯氨谬败计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 42 Converting A Texture Image OpenGL requires texture dimensions to be powers of 2 If dimensions of image are not powers of 2 gluScaleImage( format, w_in, h_in,

45、 type_in, *data_in, w_out, h_out, type_out, *data_out ); data_in is source image data_out is for destination image Image interpolated and filtered during scaling 凸嘉票夫栽液沪谈敲社浆堑挽罕烛荣的羞宇契臆梅角闺妈谦靖价双顽浴鹰计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u

46、t e r g r a p h i c s 课件 1 8 43 Based on parametric texture coordinates glTexCoord*() specified at each vertex s t 1, 1 0, 1 0, 01, 0 (s, t) = (0.2, 0.8) (0.4, 0.2) (0.8, 0.4) A BC a b c Texture SpaceObject Space Mapping a Texture 展钓亥捐绣遭衫永莆檀合后脖祖稠嘴褪沪豪徘匡慧沮卓钙飞会问肮穴藏塔计算

47、机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 44 Typical Code glBegin(GL_POLYGON); glColor3f(r0, g0, b0); /if no shading used glNormal3f(u0, v0, w0); / if shading used glTexCoord2f(s0, t0); glVertex3f(x0, y0, z0); glColor3f(r1, g1, b1); glNormal3

48、f(u1, v1, w1); glTexCoord2f(s1, t1); glVertex3f(x1, y1, z1); . . glEnd(); Note that we can use vertex arrays to increase efficiency 挺执鳖捕站猩奋奶杠凄烧匹署薄乃届督咏书黄禁命依古兔由炳静闽懦桅滔计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8

49、45 Interpolation OpenGL uses interpolation to find proper texels from specified texture coordinates Can be distortions good selection of tex coordinates poor selection of tex coordinates texture stretched over trapezoid showing effects of bilinear interpolation 症呼偷腥蒋洁池房冗涵趋伟这墟躬然过榜猜梢扑丑梳初偷谦县豫韩榨困贩计算机图形学 c o m p u t e r g r a p h i c s 课件 1 8 计算机图形学

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