CS559: Computer Graphics

Transcription

1 CS559: Compute Gaphics Lectue 7: Textue Mapping Li Zhang Sping 008 Many slides fom Ravi Ramamoothi, Columbia Univ, Geg Humpheys, UVA and Rosalee Wolfe, DePaul tutoial teaching textue mapping visually, Jingyi Yu, U Kentucky.

2 Today Continue on Textue mapping Reading Redbook: Ch 9, Ch 6 (Blending only) (highly ecommended) Molle and Haines: Real Time Rendeing, 3e, Ch 6 Linux: /p/couse/cs559 lizhang/public/eadings/6_textue.pdf Windows: P:\couse\cs559 lizhang\public\eadings\6_textue.pdf (optional) Shiley: Ch

3 Pojective (slide pojecto) Textue GL_OBJECT_LINEAR vs GL_EYE_LINEAR

4 Bump map vs Displacement map Figue 6.4 and 30 fom RTR book

5 Displacement map in a scene

6 Solid textues y x z Use model space coodinates to index into a 3D textue Like caving the object fom the mateial One difficulty of solid textuing is coming up with the textues.

7 Solid textues (cont'd) Hee's an example fo a vase cut fom a solid mable textue: Solid mable textue by Ken Pelin

8 Envionment Maps Images fom Illumination and Reflection Maps: Simulated Objects in Simulated and Real Envionments Gene Mille and C. Robet Hoffman SIGGRAPH 1984 Advanced Compute Gaphics Animation Couse Notes

9 Envionment Maps Instead of using tansfomed vetices to index the pojected textue', we can use tansfomed suface nomal s to compute indices into the textue map. These sots of mapping can be used to simulate eflections, and othe shading effects. This appoach is not completely accuate. It assumes that all eflected ays begin fom the same point, and that all objects in the scene ae the same distance fom that point. 4/9/008 Lectue 0 9

10 Applications of Envionment Map "Inteface", coutesy of Lance Williams, 1985 williams_obot4.mov Teminato, 1991 Moe histoy info on Reflectance map

11 Sphee Mapping Basics OpenGL povides special suppot fo a paticula fom of Nomal mapping called sphee mapping. It maps the nomals of the object to the coesponding nomal of a sphee. It uses a textue map of a sphee viewed fom infinity to establish the colo fo the nomal. 4/9/008 Lectue 0 11

12 Lectue 0 4/9/008 1 Sphee Mapping Mapping the nomal to a point on the sphee n v v 1 n 1 1 n 3 v 3 3

13 4/9/008 Lectue 0 13 Sphee Mapping Mapping the nomal to a point on the sphee + = + = z y x v αn 1 ' 1 ' + = + = p t p s y x 1 3 n 3 v 3 n v n 1 v 1 n v v n v n = α + = ) ( Recall: n v (-1,-1) (1,1) = 0 1 t s t s n 1 )1 ( = = + z y x p p p p n n z y x α α p t p s y x = = 1 ' 1 ' + = + = t t s s

14 OpenGL code Example // this gets inseted whee the textue is ceated gltexgeni(gl_s, GL_TEXTURE_GEN_MODE, (int) GL_SPHERE_MAP); gltexgeni(gl_t, GL_TEXTURE_GEN_MODE, (int) GL_SPHERE_MAP); glenable(gl_texture_d); glenable(gl_texture_gen_s); glenable(gl_texture_gen_t); Without a mio ball, whee to get envionment map images? When doesn t EM wok well? Flat/plana suface In paticula unde othogaphic pojection

15 What s the Best Map? A sphee map is not the only epesentation choice fo envionment maps. Thee ae altenatives, with moe unifom sampling popeties, but they equie diffeent nomal to textue mapping functions. 4/9/008 Lectue 0 15

16 Multi Textuing

17 Intepolating Textues Fom day to night Why Multi textuing Implementing Bump maps Ceate textue fo diffuse coefficient, light vecto, and nomal maps: kd * max(l n, 0)

18 Multi Textue: OpenGL Gluint textue0, textue1; //in Initi() Load in images, Initialize textues as befoe //in Display() do the following 4/9/008 Lectue 0 18

19 Combining Textues glactivetextue( GL_TEXTURE0 ); glenable( GL_TEXTURE_D ); glbindtextue(gl_texture_d, texname0); gltexenvi( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE ); glactivetextue( GL_TEXTURE1 ); glenable( GL_TEXTURE_D ); glbindtextue(gl_texture_d, texname1); int choice = 0; if (choice == 0) //modulate the two textues { gltexenvi( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE ); } else if (choice == 1) //intepolate the two textues using the alpha of cuent pimay colo { gltexenvi( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_COMBINE ); gltexenvi( GL_TEXTURE_ENV, GL_COMBINE_RGB, GL_INTERPOLATE ); gltexenvi( GL_TEXTURE_ENV, GL_SRC0_RGB, GL_TEXTURE1); gltexenvi( GL_TEXTURE_ENV, GL_SRC1_RGB, GL_PREVIOUS); gltexenvi( GL_TEXTURE_ENV, GL_SRC_RGB, GL_PRIMARY_COLOR); gltexenvi( GL_TEXTURE_ENV, GL_OPERAND0_RGB, GL_SRC_COLOR); gltexenvi( GL_TEXTURE_ENV, GL_OPERAND1_RGB, GL_SRC_COLOR); gltexenvi( GL_TEXTURE_ENV, GL_OPERAND_RGB, GL_SRC_ALPHA); } else //disable the second textue { glactivetextue(gl_texture1); gldisable(gl_texture_d); } // continue on the ight glcolo4f(0,0,0,0.); glbegin(gl_quads); glmultitexcoodf(gl_texture0, 0.0, 0.0); glmultitexcoodf(gl_texture1, 0.0, 0.0); glvetex3f(.0, 1.0, 0.0); glmultitexcoodf(gl_texture0, 0.0, 1.0); glmultitexcoodf(gl_texture1, 0.0, 1.0); glvetex3f(.0, 1.0, 0.0); glmultitexcoodf(gl_texture0, 1.0, 1.0); glmultitexcoodf(gl_texture1, 1.0, 1.0); glvetex3f(0.0, 1.0, 0.0); glmultitexcoodf(gl_texture0, 1.0, 0.0); glmultitexcoodf(gl_texture1, 1.0, 0.0); glvetex3f(0.0, 1.0, 0.0); glend();

20 Diffeent Combinations fo diffeent apps Intepolate fo fade in fade out between textues Night and day Dot poduct followed by modulation fo bump map /simplebump.html

21 Multi Textue: OpenGL Each textue unit (GL_TEXTURE*) has its own state: Textue image Envionment mode Filteing paametes Textue matix stack Automatic textue coodinate geneation Ceate visual effect using you imagination.

22 GL Extensions Multi textuing is not suppoted in visual studio. Need to download GL extension manages: GLEE stone.com/glee.php The "Easy" Gl Extension manage. GLEW The Open GL Extension Wangle. Moe info: 1/GlExtensions.htm

23 Textue animation Moving wate textue to simulate flow zoom, otation, and sheaing image on a suface Fading in and fading out (Blending mable to skin) with multi textuing