# texture wrapping with openGL **URL:** \ **Category:** Uncategorized\ **Created:** [November 4, 2008, 9:48pm UTC](https://psychtoolbox.discourse.group/t/texture-wrapping-with-opengl/1806 "2008-11-04T21:48:32Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![Allen\_Ingling](https://avatars.discourse-cdn.com/v4/letter/a/a183cd/32.png) [@Allen\_Ingling](https://psychtoolbox.discourse.group/u/Allen_Ingling)\ **Post date:** [November 4, 2008, 9:48pm UTC](https://psychtoolbox.discourse.group/t/texture-wrapping-with-opengl/1806/1 "2008-11-04T21:48:32Z")
Hi everyone I'm trying to wrap a texture to a sphere using openGL. My aim is a gray and white checkers board texture. I'm getting odd textures, like a striped sphere. I've looked at the demos but in my case Im generated my own texture not loading an image. Here are the relevant parts of my code: The texture: texSize = 512; soccerBall = zeros(texSize,texSize,3); for i = 1: texSize for j = 1: texSize a = uint8(bitand(i,8)==0); b = uint8(bitand(j,8)==0); c = (a^b)\*255; soccerBall(i,j,1) = c; soccerBall(i,j,2) = c; soccerBall(i,j,3) = c; end end InitializeMatlabOpenGL(1); Screen('BeginOpenGL', displayParams.window); glEnable(GL\_TEXTURE\_2D); glMatrixMode(GL\_PROJECTION); glPushMatrix(); glLoadIdentity(); %%% Reset The Modelview Matrix gluPerspective(displayParams.windowRect(4),displayParams.aspectRatio, 1.0, 3\*2.0); glMatrixMode(GL\_MODELVIEW); glPushMatrix(); %% Push The Matrix Onto The Stack glLoadIdentity(); %%/ Reset The Modelview Matrix glClearColor(0.5, 0.5, 0.5, 1.0); %%// Background glClearDepth(0.0); mysphere = gluNewQuadric; gluQuadricTexture(mysphere, GL\_TRUE); glTexGeni(GL\_S, GL\_TEXTURE\_GEN\_MODE, GL\_SPHERE\_MAP); glTexGeni(GL\_T, GL\_TEXTURE\_GEN\_MODE, GL\_SPHERE\_MAP); glColor3f(0.8, 0.8, 0.8); gluQuadricNormals(mysphere, GL\_SMOOTH); glEnable(GL\_TEXTURE\_2D); glShadeModel(GL\_SMOOTH); glEnable(GL\_DEPTH\_TEST); glDepthFunc(GL\_LEQUAL); glHint(GL\_PERSPECTIVE\_CORRECTION\_HINT, GL\_NICEST); glLightfv(GL\_LIGHT0, GL\_AMBIENT, [3 3 3 1]); glLightfv(GL\_LIGHT0, GL\_DIFFUSE, [3 3 3 1]); glLightfv(GL\_LIGHT0, GL\_POSITION, [0 -2 -1 1]); tex = glGenTextures(1); glBindTexture(GL\_TEXTURE\_2D, tex); glTexParameteri(GL\_TEXTURE\_2D, GL\_TEXTURE\_WRAP\_S, GL\_REPEAT); glTexParameteri(GL\_TEXTURE\_2D, GL\_TEXTURE\_WRAP\_T, GL\_REPEAT); glTexParameteri(GL\_TEXTURE\_2D, GL\_TEXTURE\_MAG\_FILTER, GL\_LINEAR); glTexParameteri(GL\_TEXTURE\_2D, GL\_TEXTURE\_MIN\_FILTER, GL\_LINEAR); glTexImage2D(GL\_TEXTURE\_2D,0,GL\_LUMINANCE,texSize,texSize,0,GL\_RGB,GL\_UNSIGNED \_BYTE,soccerBall); glMatrixMode(GL\_PROJECTION); glLoadIdentity; glColor3f(0.8, 0.8, 0.8); gluQuadricNormals(mysphere, GL\_SMOOTH); glEnable(GL\_TEXTURE\_2D); gluPerspective(25,1/aspectRatio,0.1,100); glMatrixMode(GL\_MODELVIEW); glLoadIdentity; gluLookAt(3,3,5,0,0,0,0,1,0); glClearColor(0.5,0.5,0.5,0); Any pointers or suggestions are appreciated ---
**Author:** ![mariokleiner](https://avatars.discourse-cdn.com/v4/letter/m/13edae/32.png) [@mariokleiner](https://psychtoolbox.discourse.group/u/mariokleiner)\ **Post date:** [November 5, 2008, 2:59am UTC](https://psychtoolbox.discourse.group/t/texture-wrapping-with-opengl/1806/2 "2008-11-05T02:59:50Z")
It's simpler than that, because the line > \> gluQuadricTexture(mysphere, GL\_TRUE); already creates proper texture coordinates for the sphere. You don't need GL\_SPHERE\_MAP, and if i remember correctly, using it is a bit more complex than that 2 calls. Try this: edit MinimalisticOpenGLDemo.m then replace line 271 (the imread() command), by this to create a standard Matlab checkerboard image: myimg = double(checkerboard(16, 32, 32)\>0.5) \* 255; Save and run the demo and you'll see a nice checkerboard-textured rotating sphere. To reduce aliasing, you can replace the line glTexParameteri(gltextarget, GL.TEXTURE\_MIN\_FILTER, GL.LINEAR); by glTexParameteri(gltextarget, GL.TEXTURE\_MIN\_FILTER, GL.LINEAR\_MIPMAP\_LINEAR); and add this after the glBindTexture(gltextarget, gltex); command: glGenerateMipmapEXT(GL.TEXTURE\_2D); This will enable trilinear filtering for improved customer satisfaction - or throw an error if your hardware is too old to support glGenerateMipmapExt, in which case you'll need to learn about gluBuild2DMipmaps(), or simply look into the corresponding parts of ShepardZoomDemo.m, for the old-style "more hazzle, but runs everywhere" method of creating mipmaps. good luck, -mario > --- In [psychtoolbox@yahoogroups.com](mailto:psychtoolbox@yahoogroups.com), "mniprog" \ wrote: > \> > \> Hi everyone I'm trying to wrap a texture to a sphere using openGL. My aim is a gray and > \> white checkers board texture. I'm getting odd textures, like a striped sphere. I've > looked > \> at the demos but in my case Im generated my own texture not loading an image. Here > are > \> the relevant parts of my code: > \> > \> The texture: > \> > \> texSize = 512; > \> > \> soccerBall = zeros(texSize,texSize,3); > \> for i = 1: texSize > \> for j = 1: texSize > \> > \> a = uint8(bitand(i,8)==0); > \> b = uint8(bitand(j,8)==0); > \> c = (a^b)\*255; > \> soccerBall(i,j,1) = c; > \> soccerBall(i,j,2) = c; > \> soccerBall(i,j,3) = c; > \> > \> end > \> end > \> > \> > \> > \> InitializeMatlabOpenGL(1); > \> Screen('BeginOpenGL', displayParams.window); > \> glEnable(GL\_TEXTURE\_2D); > \> glMatrixMode(GL\_PROJECTION); > \> glPushMatrix(); > \> glLoadIdentity(); %%% Reset The Modelview Matrix > \> gluPerspective(displayParams.windowRect(4),displayParams.aspectRatio, 1.0, 3\*2.0); > \> glMatrixMode(GL\_MODELVIEW); > \> glPushMatrix(); %% Push The Matrix Onto The Stack > \> glLoadIdentity(); %%/ Reset The Modelview Matrix > \> glClearColor(0.5, 0.5, 0.5, 1.0); %%// Background > \> glClearDepth(0.0); > \> > \> mysphere = gluNewQuadric; > \> gluQuadricTexture(mysphere, GL\_TRUE); > \> > \> glTexGeni(GL\_S, GL\_TEXTURE\_GEN\_MODE, GL\_SPHERE\_MAP); > \> glTexGeni(GL\_T, GL\_TEXTURE\_GEN\_MODE, GL\_SPHERE\_MAP); > \> > \> glColor3f(0.8, 0.8, 0.8); > \> gluQuadricNormals(mysphere, GL\_SMOOTH); > \> glEnable(GL\_TEXTURE\_2D); > \> > \> glShadeModel(GL\_SMOOTH); > \> glEnable(GL\_DEPTH\_TEST); > \> glDepthFunc(GL\_LEQUAL); > \> glHint(GL\_PERSPECTIVE\_CORRECTION\_HINT, GL\_NICEST); > \> glLightfv(GL\_LIGHT0, GL\_AMBIENT, [3 3 3 1]); > \> glLightfv(GL\_LIGHT0, GL\_DIFFUSE, [3 3 3 1]); > \> glLightfv(GL\_LIGHT0, GL\_POSITION, [0 -2 -1 1]); > \> > \> tex = glGenTextures(1); > \> glBindTexture(GL\_TEXTURE\_2D, tex); > \> > \> glTexParameteri(GL\_TEXTURE\_2D, GL\_TEXTURE\_WRAP\_S, GL\_REPEAT); > \> glTexParameteri(GL\_TEXTURE\_2D, GL\_TEXTURE\_WRAP\_T, GL\_REPEAT); > \> glTexParameteri(GL\_TEXTURE\_2D, GL\_TEXTURE\_MAG\_FILTER, GL\_LINEAR); > \> glTexParameteri(GL\_TEXTURE\_2D, GL\_TEXTURE\_MIN\_FILTER, GL\_LINEAR); > \> > \> > \> > glTexImage2D(GL\_TEXTURE\_2D,0,GL\_LUMINANCE,texSize,texSize,0,GL\_RGB,GL\_UNSIGNED > \> \_BYTE,soccerBall); > \> > \> > \> glMatrixMode(GL\_PROJECTION); > \> glLoadIdentity; > \> > \> glColor3f(0.8, 0.8, 0.8); > \> gluQuadricNormals(mysphere, GL\_SMOOTH); > \> glEnable(GL\_TEXTURE\_2D); > \> gluPerspective(25,1/aspectRatio,0.1,100); > \> glMatrixMode(GL\_MODELVIEW); > \> glLoadIdentity; > \> gluLookAt(3,3,5,0,0,0,0,1,0); > \> glClearColor(0.5,0.5,0.5,0); > \> > \> > \> > \> Any pointers or suggestions are appreciated > \>