texture.cpp

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// Texture handling

#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <string.h>
#include <GL/glu.h>

#include "config.h"
#include "texture.h"

// Textures file names
static const char *g_texfiles[TEX_N] = {
  "rock.raw_256x256_rgba_byte",
  "snow.raw_256x256_rgba_byte",
  "grass.raw_256x256_rgba_byte",
  "sand.raw_256x256_rgba_byte"
};

// Texture handles
static GLuint g_handles[TEX_N];
// Texture data
typedef unsigned char rgba[4];
typedef rgba teximage[ 256*256 ];
static teximage g_textures[TEX_N];


// Initialize all textures
void initTextures()
{
  // Generate handles
  glGenTextures( TEX_N, g_handles );

  // Load textures
  for (int i=0; i<TEX_N; i++) {

    // Generate filename
    char filename[200];
    strcpy( filename, g_strResourceDir );
    strcat( filename, g_texfiles[i] );

    // Open and read file (binary mode)
    FILE *f = fopen( filename, "rb" );
    if (f == NULL) {
      printf( "Error opening texture file %s\n.", g_texfiles[i] );
      exit(1);
    }

    int n = fread( g_textures[i], 4, 256*256, f );
    if (n != 256*256) {
      printf( "Error reading texture file %s: Only %i pixels read.\n",
              g_texfiles[i], n );
    }
    else {
      printf( "Successfully loaded texture %s.\n", g_texfiles[i] );
    }

    // Load texture image to OpenGL
    glBindTexture( GL_TEXTURE_2D, g_handles[i] );
    // Build all mipmap stages
    gluBuild2DMipmaps( GL_TEXTURE_2D, GL_RGBA, 256, 256, GL_RGBA, GL_UNSIGNED_BYTE, g_textures[i] );

    // Set filtering modes
    // LINEAR_MIPMAP_LINEAR specifies the highest quality mode, sometimes called
    // "trilinear filtering". Anisotropic is even better, but not yet officially supported in OpenGL.
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR );
    glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
  }
}

// Delete all textures
void deleteTextures()
{
  // Release handles
  glDeleteTextures( TEX_N, g_handles );
}


// Get the OpenGL texture handle of a texture
GLuint texture( TEXTURE t )
{
  assert( t>=0 && t<TEX_N );
  return g_handles[t];
}

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