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OpenGL texture artifact with Perl (but not C)

by japhy (Canon)
on Mar 05, 2005 at 21:25 UTC ( #436961=perlquestion: print w/ replies, xml ) Need Help??
japhy has asked for the wisdom of the Perl Monks concerning the following question:

Below are two identical programs. The first is written in C, and produces a checkerboard texture on a square. The second is written in Perl, and does the same thing, but with one minor artifact: a cyan pixel in the lower left corner.

Has anyone here used the OpenGL module and gotten around this very pesky bug?

/* C checkerboard */ #define GLUT_DISABLE_ATEXIT_HACK #include <windows.h> #include <GL/glut.h> #include <stdlib.h> #include <stdio.h> #define checkImageWidth 64 #define checkImageHeight 64 static GLubyte checkImage[checkImageHeight][checkImageWidth][4]; static GLuint texName; void makeCheckImage(void) { int i, j, c; for (i = 0; i < checkImageHeight; i++) { for (j = 0; j < checkImageWidth; j++) { c = ((((i&0x8)==0)^((j&0x8))!=0))*255; checkImage[i][j][0] = (GLubyte) c; checkImage[i][j][1] = (GLubyte) c; checkImage[i][j][2] = (GLubyte) 0; checkImage[i][j][3] = (GLubyte) 255; } } } void init(void) { glClearColor (0.0, 0.0, 0.0, 0.0); glShadeModel(GL_FLAT); glEnable(GL_DEPTH_TEST); makeCheckImage(); glPixelStorei(GL_UNPACK_ALIGNMENT, 1); glGenTextures(1, &texName); glBindTexture(GL_TEXTURE_2D, texName); 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_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, checkImageWidth, checkImage +Height, 0, GL_RGBA, GL_UNSIGNED_BYTE, checkImage); } void display(void) { glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glEnable(GL_TEXTURE_2D); glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL); glBindTexture(GL_TEXTURE_2D, texName); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); glTranslatef(0.0, 0.0, -2.0); glBegin(GL_QUADS); glTexCoord2f(0.0, 0.0); glVertex3f(-1.0, -1.0, 1.0); glTexCoord2f(0.0, 1.0); glVertex3f(-1.0, 1.0, 1.0); glTexCoord2f(1.0, 1.0); glVertex3f(1.0, 1.0, 1.0); glTexCoord2f(1.0, 0.0); glVertex3f(1.0, -1.0, 1.0); glEnd(); glFlush(); glDisable(GL_TEXTURE_2D); } void reshape(int w, int h) { glViewport(0, 0, (GLsizei) w, (GLsizei) h); glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluPerspective(112.5, (GLfloat) w/(GLfloat) h, 0.1, 30.0); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); glTranslatef(0.0, 0.0, -2.0); } void keyboard (unsigned char key, int x, int y) { switch (key) { case 27: exit(0); break; default: break; } } int main(int argc, char** argv) { glutInit(&argc, argv); glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH); glutInitWindowSize(250, 250); glutInitWindowPosition(100, 100); glutCreateWindow(argv[0]); init(); glutDisplayFunc(display); glutReshapeFunc(reshape); glutKeyboardFunc(keyboard); glutMainLoop(); return 0; }
#!/usr/bin/perl use OpenGL ':all'; use strict; use warnings; my $checker; main(); sub init { glClearColor(0,0,0,0); glShadeModel(GL_FLAT); glEnable(GL_DEPTH_TEST); my $bm; glPixelStorei(GL_UNPACK_ALIGNMENT, 1); glGenTextures_s(1, $checker); $checker = unpack "I", $checker; for my $i (0 .. 63) { for my $j (0 .. 63) { my $c = ((($i & 8) == 0) ^ (($j & 8) != 0)) * 255; $bm .= pack "C4", $c, $c, 0, 255; } } glBindTexture(GL_TEXTURE_2D, $checker); 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_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glTexImage2D_s( GL_TEXTURE_2D, 0, GL_RGBA, 64, 64, 0, GL_RGBA, GL_UNSIGNED_BYTE, $bm, ); } sub display { glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glEnable(GL_TEXTURE_2D); glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL); glBindTexture(GL_TEXTURE_2D, $checker); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); glTranslatef(0.0, 0.0, -2.0); glBegin(GL_QUADS); glTexCoord2f(0.0, 0.0); glVertex3f(-1.0, -1.0, 1.0); glTexCoord2f(0.0, 1.0); glVertex3f(-1.0, 1.0, 1.0); glTexCoord2f(1.0, 1.0); glVertex3f(1.0, 1.0, 1.0); glTexCoord2f(1.0, 0.0); glVertex3f(1.0, -1.0, 1.0); glEnd(); glFlush(); glDisable(GL_TEXTURE_2D); glutSwapBuffers(); } sub reshape { my ($w, $h) = @_; glViewport(0, 0, $w, $h); glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluPerspective(112.5, $w/$h, 0.01, 30.0); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); glTranslatef(0.0, 0.0, -3.0); } sub keyboard { my ($key, $x, $y) = @_; if ($key == 27) { exit } } sub main { glutInit(); glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH); glutInitWindowSize(250, 250); glutInitWindowPosition(100, 100); glutCreateWindow($0); init(); glutDisplayFunc(\&display); glutReshapeFunc(\&reshape); glutKeyboardFunc(\&keyboard); glutMainLoop(); return 0; }
_____________________________________________________
Jeff japhy Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and perl hacker
How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart

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Re: OpenGL texture artifact with Perl (but not C)
by fglock (Vicar) on Mar 06, 2005 at 04:31 UTC

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