Code: 3d_underwater_world/textures.cpp

This is an example OpenGL SDL application which creates an animated 3D underwater world (screenshot), with "Thunderbird 4" with headlights moving on a spline path, a randomly generated sand terrain, sunken ship/submarine/treasure chest models, and swaying fish and seaweed. It is designed to demonstrate basic OpenGL features, and the structure is as follows:

#include "textures.h"

// load an SDL surface into an OpenGL texture.
GLuint SDL_GL_LoadTexture(SDL_Surface *surface, GLfloat *texcoord);

// constructor
// opens an image file and stores it in memory
Texture::Texture(const char *file) 
{
    // load image file
    SDL_Surface *surface = IMG_Load(file);
    
    // create opengl texture
    GLfloat texcoord[4];
    tex = SDL_GL_LoadTexture(surface, texcoord);
    minx = texcoord[0];
    miny = texcoord[1];
    maxx = texcoord[2];
    maxy = texcoord[3];
    
    // delete sdl image
    SDL_FreeSurface(surface);
}

// destructor
Texture::~Texture()
{
    GLuint ts[] = { tex };
    glDeleteTextures( 1, &tex );
}

/* Taken from texture.c in example on shaders COMP3004 website
* -------------------------------------------------------------------
* QUOTE STARTS
* ------------------------------------------------------------------/

/*
Return power of 2 greater than input.
*/
static int power_of_two(int input)
{
	int value = 1;

	while ( value < input ) {
		value <<= 1;
	}
	return value;
}

/*
Load an SDL surface into an OpenGL texture.
*/
GLuint SDL_GL_LoadTexture(SDL_Surface *surface, GLfloat *texcoord)
{
	GLuint texture;
	int w, h;
	SDL_Surface *image;
	SDL_Rect area;
	Uint32 saved_flags;
	Uint8  saved_alpha;
    static GLint texture_base = 0;
	w = power_of_two(surface->w);/* Use the surface width and height expanded to powers of 2 */
	h = power_of_two(surface->h);
	texcoord[0] = 0.0f;			/* Min X */
	texcoord[1] = 0.0f;			/* Min Y */
	texcoord[2] = (GLfloat)surface->w / w;	/* Max X */
	texcoord[3] = (GLfloat)surface->h / h;	/* Max Y */

	image = SDL_CreateRGBSurface(
			SDL_SWSURFACE,
			w, h,
			32,
#if SDL_BYTEORDER == SDL_LIL_ENDIAN /* OpenGL RGBA masks */
			0x000000FF,
			0x0000FF00,
			0x00FF0000,
			0xFF000000
#else
			0xFF000000,
			0x00FF0000,
			0x0000FF00,
			0x000000FF
#endif
		       );
	if ( image == NULL ) {
		return 0;
	}
	
	/* Save the alpha blending attributes */
	saved_flags = surface->flags&(SDL_SRCALPHA|SDL_RLEACCELOK);
	saved_alpha = surface->format->alpha;
	if ( (saved_flags & SDL_SRCALPHA) == SDL_SRCALPHA ) {
		SDL_SetAlpha(surface, 0, 0);
	}

	/* Copy the surface into the GL texture image */
	area.x = 0;
	area.y = 0;
	area.w = surface->w;
	area.h = surface->h;
	SDL_BlitSurface(surface, &area, image, &area);

	/* Restore the alpha blending attributes */
	if ( (saved_flags & SDL_SRCALPHA) == SDL_SRCALPHA ) {
		SDL_SetAlpha(surface, saved_flags, saved_alpha);
	}
	
	//SDL_SetColorKey(image, SDL_SRCCOLORKEY, SDL_MapRGB(image->format, 0, 186, 171));
	//SDL_SetAlpha(image, SDL_RLEACCEL|SDL_SRCALPHA, 50);

	/* Create an OpenGL texture for the image */
//	glGenTextures(1, &texture); // generate a texture number
	texture = texture_base;
	texture_base++;
	glBindTexture(GL_TEXTURE_2D, texture); //Map specific texture to the 2D texture
	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,
		     w, h,
		     0,
		     GL_RGBA,
		     GL_UNSIGNED_BYTE,
		     image->pixels);
	return texture;
}
/*
* ------------------------------------------------------------------
* QUOTE ENDS
* ------------------------------------------------------------------
*/

3D Underwater World (using OpenGL and SDL)

textures.cpp