CS559: Computer Graphics

Transcription

1 CS559: Computer Grphic Lecture 7: Texture Mpping Li Zhng Spring 008 Mn lide from Rvi Rmmoorthi, Columbi Univ, Greg Humphre, UVA nd Rolee Wolfe, DePul tutoril teching texture mpping viull, Jingi Yu, U Kentuck.

2 Tod Continue on Texture mpping Reding Redbook: Ch 9 highl recommended Moller nd Hine: Rel Time Rendering, 3e, Ch 6 Linux: /p/coure/c559 lizhng/public/reding/6_texture.pdf Windo: P:\coure\c559 lizhng\public\reding\6_texture.pdf optionl Shirle: Ch.4.8

3 Artifct McMilln demo of thi i t Another exmple Wht rtifct do ou ee? Wh? Hint: problem i in interpolting prmeter

4 t ide: Gourud interp. of texcoord Scn line I I I 3 3 I b I I Replce I to u, v, nd, then compute u/, nd v/ I I I + = b b b x x x x I x x I I + = I I I b + =

5 t ide: Gourud interp. of texcoord Scn line 3 v v v + = u u = Do me thing for point b. From nd b, interpolte for + = u u u + = v v =,, z v u =,, z v u =,, z v u =,, z v u =,, b b b b z v u =,, z v u =

6 Perpective Correct Interpoltion In hort Rther thn interpolting u nd v directl, interpolte u / z nd v / z Thee do interpolte correctl in creen pce Alo need to interpolte /z nd multipl per pixel In prctice: e keep / z So interpolte u nd v nd, nd compute u = u/ nd v = v/ for ech pixel Thi unfortuntel involve divide per pixel

7 Texture Mpping Liner interpoltion of texture coordinte Correct interpoltion ith perpective divide 37/F98/Lecture/Slide4.html Hill Figure 8.4

8 Wh don t e notice? Trditionl creen pce Gournd hding i rong. Hoever, ou uull ill not notice becue the trnition in color i ver mooth And e don't kno ht the right color hould be n, ll e cre bout i prett picture. There re ome ce here the error in Gournd hding become obviou. When do e notice? When itching beteen different level of detil repreenttion At "T" joint.

9 Deling ith Incorrect Interpoltion You cn reduce the perceived rtifct of non perpective correct interpoltion b ubdividing the texture mpped tringle into mller tringle h doe thi ork?. But, fundmentll the creen pce interpoltion of projected prmeter i inherentl fled

10 Outline Tpe of mpping Interpolting texture coordinte Texture Rempling Broder ue of texture

11 Texture Mp Filtering Nive texture mpping lie bdl Look fmilir? int uvl = roundu * W; int vvl = roundv * H; int pix = texture.getpixeluvl, vvl; Neret Neighbor Smpling

12 Texture Mp Filtering Nive texture mpping lie bdl Look fmilir? int uvl = roundu * W; int vvl = roundv * H; int pix = texture.getpixeluvl, vvl; Actull, ech pixel mp to region in texture PIX < TEX E: interpolte biliner beteen texel vlue PIX > TEX Hrd: verge the contribution from multiple texel PIX ~ TEX Still need interpoltion!

13 Mipmp d= d=3 d= d=0 Smple u,v,d Uing tri-liner interpoltion Wht the memor overhed? Let d = PIX be meure of pixel ize Option : ue the longer edge of the qudrilterl formed b the pixel' cell to pproximte the pixel' coverge Option : ue the mx of du/dx, du/d, dv/x, dv/d Then tke logrithm

14 Storing MIP Mp One convienent method of toring MIP mp i hon belo It lo nicel illutrte the /3 overhed of mintining the MIP mp.

15 Neret Neighbor Smpling Mipmp Smpling

16 Ripmp Smple u,v,du,dv Uing Triliner => qudriliner Wht the memor overhed?

17 Wht the memor overhed? Summed Are Tble

18 Neret Neighbor Smpling Mipmp Smpling Summed Are Tble

19 Summed Are Tble Ho much torge doe ummed re tble require? Doe it require more or le ork per pixel thn MIP mp? Wht ort of lo p filter doe ummed re tble implement? No Filtering MIP mpping Summed- Are Tble

20 Other filtering method, ee Rel Time Rendering chpter 6.

21 Outline Tpe of mpping Interpolting texture coordinte Texture Rempling Texture mpping OpenGL Broder ue of texture

22 Specif texture coordinte t ech vertex, t Cnonicl coordinte here nd t re beteen 0 nd Simple OpenGL Exmple } public void Dr { glclergl_color_buffer_bit GL_DEPTH_BUFFER_BIT; gllodidentit; gltrnltedcenterx, center, depth; glmultmtrixfrottion; : // Dr Front of the Cube glenblegl_texture_d; glbegingl_quads; gltexcoordd0, ; glvertex3d.0,.0,.0; gltexcoordd, ; glvertex3d-.0,.0,.0; gltexcoordd, 0; glvertex3d-.0,-.0,.0; gltexcoordd0, 0; glvertex3d.0,-.0,.0; glend; gldiblegl_texture_d; : glfluh; gltexcoord ork like glcolor Slide from Jingi Yu

23 Initilizing Texture Mpping ttic GLubte imge[64][64][4]; ttic GLuint texnme; void initvoid { glclercolor 0.0, 0.0, 0.0, 0.0; glshdemodelgl_flat; glenblegl_depth_test; //lod in or generte imge; glpixelstoreigl_unpack_alignment, ; glgentexture, &texnme; glbindtexturegl_texture_d, texnme; } gltexprmeterigl_texture_d, GL_TEXTURE_WRAP_S, GL_REPEAT; gltexprmeterigl_texture_d, GL_TEXTURE_WRAP_T, GL_REPEAT; gltexprmeterigl_texture_d, GL_TEXTURE_MAG_FILTER, GL_NEAREST; gltexprmeterigl_texture_d, GL_TEXTURE_MIN_FILTER, GL_NEAREST; glteximgedgl_texture_d, 0, GL_RGBA, checkimgewidth, checkimgeheight, 0, GL_RGBA, GL_UNSIGNED_BYTE, imge; Level index in the Prmid

24 OpenGL Texture Peculiritie The idth nd height of Texture in OpenGL mut be poer of The prmeter pce of ech dimenion of texture rnge from [0, regrdle of the texture ctul ize. The behvior of texture indice outide of the rnge [0, i determined b the texture rp option. gltexprmeterigl_texture_d, GL_TEXTURE_WRAP_S, GL_REPEAT; gltexprmeterigl_texture_d, GL_TEXTURE_WRAP_T, GL_REPEAT; // Dr Front of the Cube glenblegl_texture_d; glbegingl_quads; gltexcoordd-, ; glvertex3d.0,.0,.0; gltexcoordd, ; glvertex3d-.0,.0,.0; gltexcoordd, -; glvertex3d-.0,-.0,.0; gltexcoordd-, -; glvertex3d.0,-.0,.0; glend; gldiblegl_texture_d; gltexprmeterigl_texture_d, GL_TEXTURE_WRAP_S, GL_CLAMP; gltexprmeterigl_texture_d, GL_TEXTURE_WRAP_T, GL_CLAMP;

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