Help With Loading TGA Files (OpenGL)

Question

Jungletoe 0 Newbie Poster

12 Years Ago

Ok, I found this code after searching for days, and to my delight it actually worked. It loads a TGA file into the memory... but I have no idea about how to load it into an OpenGL texture that I can use to texture a cube. I have literally spent days trying to work on this and I have no idea how to get it to work.

Here is the TGA Loader:
Link

Here is my overall code:

/* ************************************************************************************************ */
/* ******************************            INCLUDES           *********************************** */
/* ************************************************************************************************ */


#include "SDL.h"
#include "SDL_opengl.h"
#include "stdio.h"

const int triangle = 1;
float currentX = 0.0;
float currentY = 0.0;
float currentZ = 0.0;


/* ************************************************************************************************ */
/* *********************                     TGA LOADER         *********************************** */
/* ************************************************************************************************ */


struct STGA
{
        STGA()
        {
                data = (unsigned char*)0;
                width = 0;
                height = 0;
                byteCount = 0;
        }

	~STGA() { delete[] data; data = 0; }

	void destroy() { delete[] data; data = 0; }

        int width;
	int height;
        unsigned char byteCount;
        unsigned char* data;
};

bool loadTGA(const char *filename, STGA& tgaFile)
{
	FILE *file;
	unsigned char type[4];
	unsigned char info[6];

        file = fopen(filename, "rb");

        if (!file)
		return false;

	fread (&type, sizeof (char), 3, file);
	fseek (file, 12, SEEK_SET);
	fread (&info, sizeof (char), 6, file);

	//image type either 2 (color) or 3 (greyscale)
	if (type[1] != 0 || (type[2] != 2 && type[2] != 3))
	{
		fclose(file);
		return false;
	}

	tgaFile.width = info[0] + info[1] * 256;
	tgaFile.height = info[2] + info[3] * 256;
	tgaFile.byteCount = info[4] / 8;

	if (tgaFile.byteCount != 3 && tgaFile.byteCount != 4) {
		fclose(file);
		return false;
	}

	long imageSize = tgaFile.width * tgaFile.height * tgaFile.width * tgaFile.byteCount;

	//allocate memory for image data
	tgaFile.data = new unsigned char[imageSize];

	//read in image data
	fread(tgaFile.data, sizeof(unsigned char), imageSize, file);

	//close file
	fclose(file);

	return true;
}



/* ************************************************************************************************ */
/* *********************                CUBE DRAWER             *********************************** */
/* ************************************************************************************************ */



void drawCube(float xloc, float yloc, float zloc)
{
		glPushMatrix();
		xloc = xloc*10;
		yloc = yloc*10;
		zloc = zloc*10;
		
		STGA tgaFile;
		if(loadTGA("data/image.tga", tgaFile)){
			glBindTexture(GL_TEXTURE_2D, );
			glTranslatef(xloc, yloc, zloc);
			glBegin(GL_QUADS);
				//front face
				glColor3f(0.821, 0.525, 0.043);
				glVertex3f(10/2, 10/2, 10/2);
				glVertex3f(-10/2, 10/2, 10/2);
				glVertex3f(-10/2, -10/2, 10/2);
				glVertex3f(10/2, -10/2, 10/2);

				//left face
				glColor3f(0.821, 0.525, 0.043);
				glVertex3f(-10/2, 10/2, 10/2);
				glVertex3f(-10/2, 10/2, -10/2);
				glVertex3f(-10/2, -10/2, -10/2);
				glVertex3f(-10/2, -10/2, 10/2);

				//back face
				glColor3f(0.721, 0.425, 0.043);
				glVertex3f(10/2, 10/2, -10/2);
				glVertex3f(-10/2, 10/2, -10/2);
				glVertex3f(-10/2, -10/2, -10/2);
				glVertex3f(10/2, -10/2, -10/2);

				//right face
				glColor3f(0.821, 0.525, 0.043);
				glVertex3f(10/2, 10/2, -10/2);
				glVertex3f(10/2, 10/2, 10/2);
				glVertex3f(10/2, -10/2, 10/2);
				glVertex3f(10/2, -10/2, -10/2);

				//top face	
				glColor3f(0.419, 0.556, 0.137);
				glVertex3f(10/2, 10/2, 10/2);
				glVertex3f(-10/2, 10/2, 10/2);
				glVertex3f(-10/2, 10/2, -10/2);
				glVertex3f(10/2, 10/2, -10/2);

				//bottom face
				glColor3f(1.0, 1.0, 1.0);
				glVertex3f(10/2, -10/2, 10/2);
				glVertex3f(-10/2, -10/2, 10/2);
				glVertex3f(-10/2, -10/2, -10/2);
				glVertex3f(10/2, -10/2, -10/2);

				glEnd();
				glPopMatrix();
		}
}

/* ************************************************************************************************ */
/* *********************                      INIT              *********************************** */
/* ************************************************************************************************ */
void init()
{
	glClearColor(0.0, 0.0, 0.0, 1.0); //RGB + Alpha
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluPerspective(45, 640 / 480, 1.0, 500.0); //sets camera params
	glMatrixMode(GL_MODELVIEW);
	SDL_WM_SetCaption( "OpenGL Game", NULL );
	glShadeModel(GL_SMOOTH);
	glEnable(GL_DEPTH_TEST);
	glEnable(GL_TEXTURE_2D);
}

/* ************************************************************************************************ */
/* *********************                     DISPLAY            *********************************** */
/* ************************************************************************************************ */

void display(){
	glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
	glLoadIdentity();

	//glTranslatef(0.0, 0.0, -5.0);
	//glRotatef(angle, 1.0, 1.0, 1.0);

	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	glOrtho(-100.0f, 100.0f, -100.0f, 100.0f, -500.0f, 500.0f);
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
	glRotatef(35.264f, 1.0f, 0.0f, 0.0f);
	glRotatef(-45.0f, 0.0f, 1.0f, 0.0f);
	glScalef(1.0f, 1.0f, -1.0f);

	//current cube position
	drawCube(currentX, currentY, currentZ);
}

/* ************************************************************************************************ */
/* *********************                    MAIN                *********************************** */
/* ************************************************************************************************ */

int main( int agrc, char* args[] )
{
	SDL_Init(SDL_INIT_EVERYTHING);
	SDL_Surface* screen=SDL_SetVideoMode(600,400,32, SDL_SWSURFACE|SDL_OPENGL );
	bool running = true;
	Uint32 start;
	SDL_Event event;
	init();

	while(running)
	{
		start=SDL_GetTicks();
		if (SDL_PollEvent(&event))
		{
			if (event.type == SDL_QUIT){
				running = false;
			}

			if (event.type == SDL_KEYDOWN){
				SDLKey keyPressed = event.key.keysym.sym;
   
				switch (keyPressed)
				{
					case SDLK_ESCAPE:
						running = false;
						break;
					
					case SDLK_UP:
						currentZ++;
						break;
					
					case SDLK_DOWN:
						currentZ--;
						break;

					case SDLK_RIGHT:
						currentX++;
						break;

					case SDLK_LEFT:
						currentX--;
						break;
			
				}
			}
		}
		display();
		SDL_GL_SwapBuffers();
		if(1000/30>(SDL_GetTicks()-start))
			SDL_Delay(1000/30>(SDL_GetTicks()-start));
	}

	SDL_Quit();
	return 0;
}

All I need is to find a way to make a texture ID and make OpenGL load it into that cube in the drawCube() function.

Thanks,
Jungle

c++ opengl sdl texture tga

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Latest Post 12 Years Ago Latest Post by myk45

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myk45 48 Posting Whiz · Answer 1 · 2011-11-27T13:00:57+00:00

You need to generate a texture ID, as you have mentioned.

glGenTextures()

You need to specify the data for the texture.
glTexImage2D

You then need to specify the filtering technique you wish to use.
glTexParameter[if]

You also need to specify the texture coordinates using glTexCoord2[df]

You can look into this tutorial for a detailed explanation.
LINK