Am Freitag, 2. März 2007 schrieb [EMAIL PROTECTED]: > On Fri, 02 Mar 2007 03:26:59 -0500 Per Inge Mathisen > > <[EMAIL PROTECTED]> wrote: > >On 3/2/07, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > >> Before the hardcode of 512, it was change to > > > >BACKDROP_HACK_WIDTH, > > > >> and BACKDROP_HACK_HEIGHT (which still is 512). > >> > >> In code below this with > >> glBegin(GL_TRIANGLE_STRIP); > >> glTexCoord2f(0, 0); > >> glVertex2f(0, 0); > >> glTexCoord2f(255, 0); > >> glVertex2f(screenWidth, 0); > >> glTexCoord2f(0, 255); > >> glVertex2f(0, screenHeight); > >> glTexCoord2f(255, 255); > >> glVertex2f(screenWidth, screenHeight); > >> glEnd(); > >> > >> should not the 255 be also changed? Why is it 255 in first > > > >place? > > > >> if BACKDROP_HACK_HEIGHT = 1024, then it no look right ? > >> > >> Anybody explain why this value used? I think it is mistake? > > > >I believe those are texture coordinates that get translated into > >0.0f > >-> 1.0f. Although I must admit I am a bit mystified about how > >exactly > >this works. > > > > - Per > > I find this, > glViewport(0, 0, width, height); > glMatrixMode(GL_PROJECTION); > glPushMatrix(); > glLoadIdentity(); > glOrtho(0, width, height, 0, 1, -1); > glMatrixMode(GL_TEXTURE); > glScalef(1/256.0, 1/256.0, 1); > glMatrixMode(GL_MODELVIEW); > glLoadIdentity(); > glCullFace(GL_FRONT); > glEnable(GL_CULL_FACE); > > So we deal with glOrtho to set up coordinates. > Then map coordinates of 0 to width and 0 to height is used yes? > Then mapping should be 0 to width = 0 to 1.0, same for height. If > width=1024, height=768 = 1.0,1.0 I thinks. > glTexCoord2f(255, 255) = 255/256 right because call to > glScalef(1/256.0, 1/256.0, 1) is in the GL_TEXTURE matrix ? > > Is logic right? > If yes, then why we scale Texture matrix at all? Is it to save > time from doing division? Why 1/256? Is because original > textures are 256x256? Probably, yes. Thanks for finding this. :)
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