#!/usr/local/bin/perl
#
#          texture
#
#  This program demonstrates texture mapping  
#  An image file (wolf.ppm) is read in as the texture
#  then packed into a C array format and given to glTexImage2D 
#

BEGIN{ unshift(@INC,"../blib"); }  # in case OpenGL is built but not installed
BEGIN{ unshift(@INC,"../blib/arch"); } # 5.002 gamma needs this
BEGIN{ unshift(@INC,"../blib/lib"); } # 5.002 gamma needs this
use OpenGL;
 
$spin=0.0;

sub read_ascii_ppm{
	# reads in an ascii ppm format image file
	# returns the list (width,height,packed rgb image data)
	#
	# I'm not to familiar with the ppm file format 
	# this subroutine may not work for all valid ppm files
	#
	local($file) = @_;
	local($w,$h,$image);
	local(@image);
	open(PPM,"<$file") || die "cant open $file";
	(<PPM>);  		# the first line is just a header: "P3"
	(<PPM>);  		# The second line is a comment 
	($_=<PPM>); 		# the 3rd line gives width and height
	m/(\d+)\s+(\d+)/; 
	$w=$1 ; $h=$2 ;
	($w>=64 && $h>=64 && $w<10000 && $h<10000) || die "strange sizes $w,$h";
	($_=<PPM>);		# 4th line is depth (should be 255)
	(/255/) || die " improper depth $_";
	$image="";
	while(<PPM>) {
		chop;
		$image .= $_ . " ";
	}
	@image=split(/\s+/,$image);
	$size=$w*$h*3;
	($size == $#image +1) || die "array length $#image +1  differs from expected size $size" ; 
	$image=pack("C$size",@image);
	close(PPM);
	($w,$h,$image);
}

sub myReshape {
    # glViewport(0, 0, w, h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(60.0, 1.0 , 1.0, 30.0);

    glMatrixMode(GL_MODELVIEW);
 }

sub display{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity ();
    glTranslatef(0.0, 0.0, -2.6);

    glPushMatrix();
    glRotatef($spin,0,1,0);
    glRotatef($spin,0,0,1);
    glBegin(GL_QUADS);
    glTexCoord2f(0.0, 1.0); glVertex3f(-1.0, -1.0, 0.0);
    glTexCoord2f(0.0, 0.0); glVertex3f(-1.0, 1.0, 0.0);
    glTexCoord2f(1.0, 0.0); glVertex3f(1.0, 1.0, 0.0);
    glTexCoord2f(1.0, 1.0); glVertex3f(1.0, -1.0, 0.0);

    glPopMatrix();
    glEnd();
    glFlush();
    glXSwapBuffers();
}


glpOpenWindow(width=>200,height=>200,attributes=>[GLX_RGBA,GLX_DOUBLEBUFFER]);
glClearColor(0,0,0,1);
glColor3f (1.0, 1.0, 1.0);
glShadeModel (GL_FLAT);
myReshape();
 
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LESS);

glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
($w,$h,$image)=&read_ascii_ppm("wolf.ppm");
glTexImage2D(GL_TEXTURE_2D, 0, 3, $w,$h, 0, GL_RGB, GL_UNSIGNED_BYTE,$image);

glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
glEnable(GL_TEXTURE_2D);

while(1){$spin=$spin+1.0;display; }

