OpenGL and C++

[Jayhawker07]

So I recently started doing things with OpenGL (after completing many 2D games in SDL) and it is relatively straightforward. However I have ran into a problem, I cannot figure out how to load a texture. I have tried DevIL, SOIL, libPNG, libJPG, but either none of them work for me or I don't know how to properly implement them. I am not against writing an image loader for uncompressed bmps, but if is the route you think I should go, I will most likely need heavy assistance. Thanks!

[o1vk4iN6]

You load textures into opengl through one of the supported pixel types.

[stoffe1100]

Try do copy this and insert it into your code
http://nehe.gamedev.net/tutorial/lesson_06_texturing_update/47002/
Works just fine for my game.

Also dont forget to glEnable(GL_TEXTURE_2D);
Have you put out your texCoords?

[Jayhawker07]

The first comment didnt really help at all, and for the second comment, I tried installing the SOIL headers then putting the code into mine, (I also put the glEnable(GL_TEXTURE_2D) but I was getting a bunch of undefined errors. I am on a different computer now however so I wont be able to give you the specific ones.

[stoffe1100]

Sorry but it is pretty hard to help you without more info

[Jayhawker07]

I am going to try to be as specific as can be.

So I know this code probably isn't very efficient, it was taken from my code that I used while I was going through the swiftless tutorials. It could probably be shortened and whatnot, but that is not what I am here about, I would like to know how to get a texture on the 4.0f x 4.0f slate by using either SOIL or DevIL or a bitmap loader that I would make myself. I have tried to set them up but I can never do it completely right, so if anyone could walk me through the steps for setting it up in code::blocks it would be great.
P.S. I left out the code that I was too lazy to remove from the project that handled key events (i'm not using any).

//main.cpp
#include <GL/glut.h>
#include <GL/gl.h>
#include "keyOps.h"
#include "windowOps.h"
#include "rendering.h"


void init (void) {
    glEnable (GL_DEPTH_TEST);
    glEnable (GL_LIGHTING);
    glEnable (GL_LIGHT0);
    glEnable(GL_COLOR_MATERIAL);
}

int main( int argc, char **argv ) {

    glutInit( &argc, argv );

    glutInitDisplayMode ( GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH );

    glutInitWindowSize( 500, 500 );
    glutInitWindowPosition( 100, 100 );

    glutCreateWindow( "OpenGL" );

    init();

    glutDisplayFunc( display );
    glutIdleFunc( display );
    glutReshapeFunc(reshape);

    glutKeyboardFunc(keyPressed);
    glutKeyboardUpFunc(keyUp);

    glutSpecialFunc( keySpecial );
    glutSpecialUpFunc( keySpecialUp );

    glutReshapeFunc( reshape );

    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

    glutMainLoop();
}

//rendering.cpp
#include <GL/glut.h>
#include "windowOps.h"
#include "keyOps.h"
#include "rendering.h"

void renderPrimitive( void ) {


    glBegin(GL_QUADS);
        glVertex3f( -2.0, 2.0, 0.0 );
        glVertex3f( -2.0, -2.0, 0.0 );
        glVertex3f( 2.0, -2.0, 0.0 );
        glVertex3f( 2.0, 2.0, 0.0 );
    glEnd();

}

//rendering.h
extern bool movingUp;
extern float yLocation;
extern float yRotationAngle;

extern void renderPrimitive( void );

//windowOps.cpp
#include <GL/glut.h>
#include "windowOps.h"
#include "keyOps.h"
#include "rendering.h"

void reshape( int width, int height ) {

    glViewport(0, 0, (GLsizei)width, (GLsizei)height );

    glMatrixMode(GL_PROJECTION);

    glLoadIdentity();

    gluPerspective(60, (GLfloat)width / (GLfloat)height, 1.0, 100.0 );

    glMatrixMode(GL_MODELVIEW);
}

void display( void ) {

    keyOperations();

    glClearColor (0.0,0.0,0.0,1.0);
    glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();

    glTranslatef( 0.0f, 0.0f, -5.0f );

    gluLookAt ( 3.0, 2.0, 2.5, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);

    renderPrimitive();

    glutSwapBuffers();
}

//windowOps.h
extern void reshape( int width, int height );
extern void display( void );
extern void light();

[stoffe1100]

I have no experience at all with Glut. i'm sorry but i can't help you very much.

But basicly if youre not using glut its pretty much like this.

InitFunc()
{
 glEnable(GL_TEXTURE_2D);
 

}

RenderFunc()
{
	glEnable(GL_TEXTURE_2D);
	glBindTexture(GL_TEXTURE_2D,TileData.TexID);

	glBegin(GL_QUADS);

		glTexCoord2f(0.0f,0.0f); glVertex2f(box.x, box.y);
		glTexCoord2f(1.0f,0.0f); glVertex2f(box.x + box.w, box.y);
		glTexCoord2f(1.0f,1.0f); glVertex2f(box.x + box.w, box.y + box.h);
		glTexCoord2f(0.0f,1.0f); glVertex2f(box.x, box.y + box.h);

	glEnd();

	glDisable(GL_TEXTURE_2D);
}

[o1vk4iN6]

http://www.opengl.org/wiki/Fixed_Function_Pipeline

It also doesn't exist in opengl es 2.0 if you ever plan to use that.

[Jayhawker07]

To stoffe1100: That makes a lot of sense, but it also looks a little too easy, also where does TileData.TexID come from? Other than that that code really helped me, its just that one variable that I am confused with

[Major Tom]

1) Initialize your textures into some sort of variable or array. With my game engine I use SOIL, and have been quite happy with that.

GLuint textureList[maxTextures];
void client::loadTexts()

{
    textureList[TEXTURE_CROSSHAIR] = SOIL_load_OGL_texture(

                                         "resource/art/UI/crosshair.tga",

                                         SOIL_LOAD_AUTO,

                                         SOIL_CREATE_NEW_ID,

                                         SOIL_FLAG_INVERT_Y | SOIL_FLAG_MULTIPLY_ALPHA

                                     );
                  if(!textureList[TEXTURE_CROSSHAIR]){cout<<"TEXTURE LOAD FAILIURE: "<<SOIL_last_result()<<endl;}
.....etc
}

Then make sure when you go to render your quad or whatever, make sure you do:

glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D,textureList[TEXTURE_CROSSHAIR]);

This is simplified, but that is the basic loading and usage of textures.
Edit: Look up the soil loading flags for more information on loading textures.