Programming Forums > Application Development > C

Johnny Redburn · Jun 2nd, 2006, 10:14 AM

Hiya

Im writing a program in C using openGL (GLUT) and im having a little trouble with the function to process textures (RAW files). It compiles ok but when i bind the texture in my display function and apply it to a quad it does not display it at runtime (just has a simple RGB default colour i had assigned with glColor3f). It has to be because its not allocating the memory correctly with the malloc i think? but i cant think of a way to just get it working, can anyone please maybe help me.. Pretty please? Im getting really frustrated lol.

Below is the texture processing function:

(Toggle Plain Text)

// load a 256x256 RGB .RAW file as a texture
GLuint LoadTextureRAW( const char * filename, int wrap ) {

  GLuint texture;
  int width, height;
  BYTE * data;
  FILE * file;

  // open texture data
  file = fopen( filename, "rb" );
  if ( file == NULL ) return 0;

  // allocate buffer
  width	 = 256;
  height = 256;
  data = (BYTE*)malloc( width * height * 3 );  // <---- is this right?

  // read texture data
  fread( data, width * height * 3, 1, file );
  fclose( file );

  // allocate a texture name
  glGenTextures( 1, &texture );

  // select our current texture
  glBindTexture( GL_TEXTURE_2D, texture );

  // select modulate to mix texture with color for shading
  glTexEnvf( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE );

  // when texture area is small, bilinear filter the closest MIP map
  glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST );
  // when texture area is large, bilinear filter the first MIP map
  glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );

  // if wrap is true, the texture wraps over at the edges (repeat)
  //       ... false, the texture ends at the edges (clamp)
  glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, wrap ? GL_REPEAT : GL_CLAMP );
  glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, wrap ? GL_REPEAT : GL_CLAMP );

  // build our texture MIP maps
  gluBuild2DMipmaps( GL_TEXTURE_2D, 3, width, height, GL_RGB, GL_UNSIGNED_BYTE, data );

  // free buffer
  free( data );

  return texture;
}

Im using it like this (just showing the parts that matter):

(Toggle Plain Text)

GLuint texture;
texture = LoadTextureRAW("bush.raw", TRUE);

glBindTexture(GL_TEXTURE_2D, texture);

glBegin(GL_QUADS);				
	glColor3f(0.0, 0.6, 0.0); //Just the default colour
	glTexCoord2f(0.0,0.0);
	glVertex3f(-1000.0, 0.0, 1000.0);
	glTexCoord2f(0.0,1.0);
	glVertex3f(1000.0, 0.0, 1000.0);
	glTexCoord2f(1.0,1.0); 
	glVertex3f(1000.0, 0.0, -1000.0);
	glTexCoord2f(1.0,0.0); 
	glVertex3f(-1000.0, 0.0, -1000.0);		
glEnd();

I really need to get this working

Thanks.

volatile · Jun 2nd, 2006, 11:11 AM

yes, your malloc is correct. However, you should always check if your memory allocation was successfull. ie check if data is NULL, and take action accordingly.

You should call glPixelStorei(GL_UNPACK_ALIGNMENT, 1); before you call gluBuild2DMipmaps. You need to tell openGL how it should unpack your image from memory. Look it up in the reference.

And then ofcourse, the most important thing, I assume you have this pice of code somewhere in the beginning of you app.

(Toggle Plain Text)

glEnable(GL_TEXTURE_2D);

Can's see anything else that needs fixing. Hope this helps.

Adak · Jun 3rd, 2006, 7:55 PM

I've always been told to use sizeof(whatever), rather than multiplying it out yourself, to avoid getting a mean bite from possible alignment adjustments of the compiler.

Adak

Jun 2nd, 2006, 10:14 AM	#1
Johnny Redburn Newbie Join Date: Jun 2006 Posts: 1 Rep Power: 0	need help with texture mapping (C and openGL) :( Hiya Im writing a program in C using openGL (GLUT) and im having a little trouble with the function to process textures (RAW files). It compiles ok but when i bind the texture in my display function and apply it to a quad it does not display it at runtime (just has a simple RGB default colour i had assigned with glColor3f). It has to be because its not allocating the memory correctly with the malloc i think? but i cant think of a way to just get it working, can anyone please maybe help me.. Pretty please? Im getting really frustrated lol. Below is the texture processing function: (Toggle Plain Text) // load a 256x256 RGB .RAW file as a texture GLuint LoadTextureRAW( const char * filename, int wrap ) { GLuint texture; int width, height; BYTE * data; FILE * file; // open texture data file = fopen( filename, "rb" ); if ( file == NULL ) return 0; // allocate buffer width = 256; height = 256; data = (BYTE)malloc( width height * 3 ); // <---- is this right? // read texture data fread( data, width * height * 3, 1, file ); fclose( file ); // allocate a texture name glGenTextures( 1, &texture ); // select our current texture glBindTexture( GL_TEXTURE_2D, texture ); // select modulate to mix texture with color for shading glTexEnvf( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE ); // when texture area is small, bilinear filter the closest MIP map glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST ); // when texture area is large, bilinear filter the first MIP map glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR ); // if wrap is true, the texture wraps over at the edges (repeat) // ... false, the texture ends at the edges (clamp) glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, wrap ? GL_REPEAT : GL_CLAMP ); glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, wrap ? GL_REPEAT : GL_CLAMP ); // build our texture MIP maps gluBuild2DMipmaps( GL_TEXTURE_2D, 3, width, height, GL_RGB, GL_UNSIGNED_BYTE, data ); // free buffer free( data ); return texture; } // load a 256x256 RGB .RAW file as a texture GLuint LoadTextureRAW( const char * filename, int wrap ) { GLuint texture; int width, height; BYTE * data; FILE * file; // open texture data file = fopen( filename, "rb" ); if ( file == NULL ) return 0; // allocate buffer width = 256; height = 256; data = (BYTE)malloc( width height * 3 ); // <---- is this right? // read texture data fread( data, width * height * 3, 1, file ); fclose( file ); // allocate a texture name glGenTextures( 1, &texture ); // select our current texture glBindTexture( GL_TEXTURE_2D, texture ); // select modulate to mix texture with color for shading glTexEnvf( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE ); // when texture area is small, bilinear filter the closest MIP map glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST ); // when texture area is large, bilinear filter the first MIP map glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR ); // if wrap is true, the texture wraps over at the edges (repeat) // ... false, the texture ends at the edges (clamp) glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, wrap ? GL_REPEAT : GL_CLAMP ); glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, wrap ? GL_REPEAT : GL_CLAMP ); // build our texture MIP maps gluBuild2DMipmaps( GL_TEXTURE_2D, 3, width, height, GL_RGB, GL_UNSIGNED_BYTE, data ); // free buffer free( data ); return texture; } Im using it like this (just showing the parts that matter): (Toggle Plain Text) GLuint texture; texture = LoadTextureRAW("bush.raw", TRUE); glBindTexture(GL_TEXTURE_2D, texture); glBegin(GL_QUADS); glColor3f(0.0, 0.6, 0.0); //Just the default colour glTexCoord2f(0.0,0.0); glVertex3f(-1000.0, 0.0, 1000.0); glTexCoord2f(0.0,1.0); glVertex3f(1000.0, 0.0, 1000.0); glTexCoord2f(1.0,1.0); glVertex3f(1000.0, 0.0, -1000.0); glTexCoord2f(1.0,0.0); glVertex3f(-1000.0, 0.0, -1000.0); glEnd(); GLuint texture; texture = LoadTextureRAW("bush.raw", TRUE); glBindTexture(GL_TEXTURE_2D, texture); glBegin(GL_QUADS); glColor3f(0.0, 0.6, 0.0); //Just the default colour glTexCoord2f(0.0,0.0); glVertex3f(-1000.0, 0.0, 1000.0); glTexCoord2f(0.0,1.0); glVertex3f(1000.0, 0.0, 1000.0); glTexCoord2f(1.0,1.0); glVertex3f(1000.0, 0.0, -1000.0); glTexCoord2f(1.0,0.0); glVertex3f(-1000.0, 0.0, -1000.0); glEnd(); I really need to get this working Thanks.

Jun 2nd, 2006, 11:11 AM	#2
volatile Newbie Join Date: Nov 2005 Posts: 18 Rep Power: 0	yes, your malloc is correct. However, you should always check if your memory allocation was successfull. ie check if data is NULL, and take action accordingly. You should call glPixelStorei(GL_UNPACK_ALIGNMENT, 1); before you call gluBuild2DMipmaps. You need to tell openGL how it should unpack your image from memory. Look it up in the reference. And then ofcourse, the most important thing, I assume you have this pice of code somewhere in the beginning of you app. (Toggle Plain Text) glEnable(GL_TEXTURE_2D); glEnable(GL_TEXTURE_2D); Can's see anything else that needs fixing. Hope this helps.

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Jun 3rd, 2006, 7:55 PM	#3
Adak Hobby Coder Join Date: May 2006 Posts: 58 Rep Power: 0	I've always been told to use sizeof(whatever), rather than multiplying it out yourself, to avoid getting a mean bite from possible alignment adjustments of the compiler. Adak

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Programming Forums > Application Development > C

need help with texture mapping (C and openGL) :(