progs/demos/lodbias.c

/*
 * GL_EXT_texture_lod_bias demo
 *
 * Thanks to Michael Vance for implementing this extension in Mesa.
 *
 * Brian Paul
 * 20 March 2000
 *
 * Copyright (C) 2000  Brian Paul   All Rights Reserved.
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
 * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */


#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <GL/glut.h>
#include <GL/glext.h>

#include "readtex.c"   /* I know, this is a hack. */

#define TEXTURE_FILE "../images/girl.rgb"

static GLfloat Xrot = 0, Yrot = -30, Zrot = 0;
static GLboolean Anim = GL_TRUE;
static GLint Bias = 0, BiasStepSign = +1; /* ints avoid fp precision problem */
static GLint BiasMin = -200, BiasMax = 500;



static void
PrintString(const char *s)
{
   while (*s) {
      glutBitmapCharacter(GLUT_BITMAP_8_BY_13, (int) *s);
      s++;
   }
}

static void Idle( void )
{
   static int lastTime = 0;
   int time = glutGet(GLUT_ELAPSED_TIME);
   int step;

   if (lastTime == 0)
      lastTime = time;
   else if (time - lastTime < 10)
      return;

   step = (time - lastTime) / 10 * BiasStepSign;
   lastTime = time;

   Bias += step;
   if (Bias < BiasMin) {
      Bias = BiasMin;
      BiasStepSign = +1;
   }
   else if (Bias > BiasMax) {
      Bias = BiasMax;
      BiasStepSign = -1;
   }

   glutPostRedisplay();
}


static void Display( void )
{
   char str[100];

   glClear( GL_COLOR_BUFFER_BIT );

   glMatrixMode( GL_PROJECTION );
   glLoadIdentity();
   glOrtho(-1, 1, -1, 1, -1, 1);
   glMatrixMode( GL_MODELVIEW );
   glLoadIdentity();
   
   glDisable(GL_TEXTURE_2D);
   glColor3f(1,1,1);
   glRasterPos3f(-0.9, -0.9, 0.0);
   sprintf(str, "Texture LOD Bias = %4.1f", Bias * 0.01);
   PrintString(str);

   glMatrixMode( GL_PROJECTION );
   glLoadIdentity();
   glFrustum( -1.0, 1.0, -1.0, 1.0, 5.0, 25.0 );
   glMatrixMode( GL_MODELVIEW );
   glLoadIdentity();
   glTranslatef( 0.0, 0.0, -8.0 );

   glPushMatrix();
   glRotatef(Xrot, 1, 0, 0);
   glRotatef(Yrot, 0, 1, 0);
   glRotatef(Zrot, 0, 0, 1);

   glEnable(GL_TEXTURE_2D);
   glTexEnvf(GL_TEXTURE_FILTER_CONTROL_EXT, GL_TEXTURE_LOD_BIAS_EXT, 0.01 * Bias);

   glBegin(GL_POLYGON);
   glTexCoord2f(0, 0);  glVertex2f(-1, -1);
   glTexCoord2f(2, 0);  glVertex2f( 1, -1);
   glTexCoord2f(2, 2);  glVertex2f( 1,  1);
   glTexCoord2f(0, 2);  glVertex2f(-1,  1);
   glEnd();

   glPopMatrix();

   glutSwapBuffers();
}


static void Reshape( int width, int height )
{
   glViewport( 0, 0, width, height );
}


static void Key( unsigned char key, int x, int y )
{
   const GLfloat step = 3.0;
   (void) x;
   (void) y;
   switch (key) {
      case 'a':
         Anim = !Anim;
         if (Anim)
            glutIdleFunc(Idle);
         else
            glutIdleFunc(NULL);
         break;
      case 'z':
         Zrot -= step;
         break;
      case 'Z':
         Zrot += step;
         break;
      case 'b':
         Bias -= 10;
         break;
      case 'B':
         Bias += 10;
         break;
      case 27:
         exit(0);
         break;
   }
   glutPostRedisplay();
}


static void SpecialKey( int key, int x, int y )
{
   const GLfloat step = 3.0;
   (void) x;
   (void) y;
   switch (key) {
      case GLUT_KEY_UP:
         Xrot -= step;
         break;
      case GLUT_KEY_DOWN:
         Xrot += step;
         break;
      case GLUT_KEY_LEFT:
         Yrot -= step;
         break;
      case GLUT_KEY_RIGHT:
         Yrot += step;
         break;
   }
   glutPostRedisplay();
}


static void Init( void )
{
   const char *exten = (const char *) glGetString(GL_EXTENSIONS);
   if (!strstr(exten, "GL_EXT_texture_lod_bias")) {
      printf("Sorry, GL_EXT_texture_lod_bias not supported by this renderer.\n");
      exit(1);
   }

   glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
   if (!LoadRGBMipmaps(TEXTURE_FILE, GL_RGB)) {
      printf("Error: could not load texture image %s\n", TEXTURE_FILE);
      exit(1);
   }

   /* mipmapping required for this extension */
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
   glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
}


int main( int argc, char *argv[] )
{
   glutInit( &argc, argv );
   glutInitWindowPosition( 0, 0 );
   glutInitWindowSize( 350, 350 );
   glutInitDisplayMode( GLUT_RGB | GLUT_DOUBLE );
   glutCreateWindow(argv[0]);
   glutReshapeFunc( Reshape );
   glutKeyboardFunc( Key );
   glutSpecialFunc( SpecialKey );
   glutDisplayFunc( Display );
   if (Anim)
      glutIdleFunc(Idle);
   Init();
   glutMainLoop();
   return 0;
}