OpenGL - Load mutliple texures in one function - c++

Question

I've already constructed a 15x15 grid of cubes with glutSolidCube(). Then i have a menu handler in which when I click "Start Game", loads the texture I used to all of the cubes, calling a custom glutSolidCube and having glTexCoord2d before each declaration of vertices, cause we can't have textures on the latter I think. For uploading the texture from an image, I'm using a STB_IMAGE_IMPLEMENTATION implementation having also a header file included. The function loadTextureFromFile(const char *filename) does the loading part.
How can I upload more textures (I want 2 more, in the same loadTextureFromFile() function preferably) and how to handle each texture with the glTexCoord2d()?
Here's my entire code:
#include<iostream>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <GL/gl.h> // openGL header
#include <GL/glu.h> // glut header
#include <GL/glut.h> // glut header
#define STB_IMAGE_IMPLEMENTATION
/////////////////////////////////////Textures==============================================/////////////////////////////////////
#include "stb_image.h"
GLuint texture; //the array for our texture
void loadTextureFromFile(const char *filename)
{
glClearColor(0.0, 0.0, 0.0, 0.0);
//glShadeModel(GL_FLAT);
//glEnable(GL_DEPTH_TEST);
unsigned int texture;
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
// set the texture wrapping/filtering options (on the currently bound texture object)
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
// load and generate the texture
int width, height, nrChannels;
unsigned char *data = stbi_load("paper.bmp", &width, &height, &nrChannels, 0);
if (data)
{
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
//glGenerateMipmap(GL_TEXTURE_2D);
}
else
{
std::cout << "Failed to load texture" << std::endl;
}
stbi_image_free(data);
}
void FreeTexture(GLuint texture)
{
glDeleteTextures(1, &texture);
}
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
static void
drawBox(GLfloat size, GLenum type)
{
static GLfloat n[6][3] =
{
{-1.0, 0.0, 0.0},
{0.0, 1.0, 0.0},
{1.0, 0.0, 0.0},
{0.0, -1.0, 0.0},
{0.0, 0.0, 1.0},
{0.0, 0.0, -1.0}
};
static GLint faces[6][4] =
{
{0, 1, 2, 3},
{3, 2, 6, 7},
{7, 6, 5, 4},
{4, 5, 1, 0},
{5, 6, 2, 1},
{7, 4, 0, 3}
};
GLfloat v[8][3];
GLint i;
v[0][0] = v[1][0] = v[2][0] = v[3][0] = -size / 2;
v[4][0] = v[5][0] = v[6][0] = v[7][0] = size / 2;
v[0][1] = v[1][1] = v[4][1] = v[5][1] = -size / 2;
v[2][1] = v[3][1] = v[6][1] = v[7][1] = size / 2;
v[0][2] = v[3][2] = v[4][2] = v[7][2] = -size / 2;
v[1][2] = v[2][2] = v[5][2] = v[6][2] = size / 2;
for (i = 5; i >= 0; i--) {
glBegin(type);
glNormal3fv(&n[i][0]);
glTexCoord2d(0.0,0.0);
glVertex3fv(&v[faces[i][0]][0]);
glTexCoord2d(0.0,1.0);
glVertex3fv(&v[faces[i][1]][0]);
glTexCoord2d(1.0,1.0);
glVertex3fv(&v[faces[i][2]][0]);
glTexCoord2d(1.0,0.0);
glVertex3fv(&v[faces[i][3]][0]);
glEnd();
}
}
void APIENTRY
myglutSolidCube(GLdouble size)
{
drawBox(size, GL_QUADS);
}
//int red_color[]={255,0,0};
//int blue_colot[]={0,0,255};
//////////////////////////////=========MENU============/////////////
enum MENU_TYPE //menu options-values
{
MENU_START,
MENU_EXIT,
};
//create the menu - Prototype
void my_createmenu(void);
// Menu handling function declaration - Prototype
void menu(int);
void init()
{ //for 3d lighting
glEnable(GL_DEPTH_TEST); //depth test
glEnable(GL_LIGHTING); //enable light from a single source
glEnable(GL_LIGHT0); //enable white light , diffuse and specular components
glEnable(GL_COLOR_MATERIAL); //track the current color
}
void display()
{
glClearColor(0.0f, 0.0f, 0.0f, 1.0f); //Black and opaque
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
//define the projection matrix just once and use the modelview matrix all other times
glMatrixMode(GL_PROJECTION); //Applies subsequent matrix operations to the projection matrix stack
glLoadIdentity();//Reset
GLint viewport[4];
glGetIntegerv(GL_VIEWPORT, viewport); //The params parameter returns four values: the x and y window coordinates of the viewport, followed by its width and height
double aspect = (double)viewport[2] / (double)viewport[3]; // y/width would be 1.0
gluPerspective(60,aspect, 1, 100); //using perspective projection
//gluOrtho2D(0.0,600.0,-60.0,600.0);
glMatrixMode(GL_MODELVIEW); //for trasformations - Applies subsequent matrix operations to the texture matrix stack
glLoadIdentity();
// move back a bit for viewer , cause of gluPerspective
glTranslatef( 0, 0, -35 );
float e=0,f=0;
//construct the grid with reference the central cube
for(int i=0;i<8;i++) {
for(int j=0;j<8;j++) {
glPushMatrix();
glTranslatef(0.0f+e,0.0f+f,0.0f); //right and below
glRotatef(20.0f,1.0f,-2.0f,0.0f); //looking 3d
glColor3ub(245, 245, 220); //Beige
glutSolidCube(2.25);
glPopMatrix();
glPushMatrix();
glTranslatef(0.0f-e,0.0f+f,0.0f); //left and below
glRotatef(20.0f,1.0f,-2.0f,0.0f); //looking 3d
glColor3ub(245, 245, 220); //Beige
glutSolidCube(2.25);
glPopMatrix();
glPushMatrix();
glTranslatef(0.0f+e,0.0f-f,0.0f); //right and up
glRotatef(20.0f,1.0f,-2.0f,0.0f); //looking 3d
glColor3ub(245, 245, 220); //Beige
glutSolidCube(2.25);
glPopMatrix();
glPushMatrix();
glTranslatef(0.0f-e,0.0f-f,0.0f); //left and up
glRotatef(20.0f,1.0f,-2.0f,0.0f); //looking 3d
glColor3ub(245, 245, 220); //Beige
glutSolidCube(2.25);
glPopMatrix();
f += -2.63;
}
f=0;
e+=2.63;
}
glutSwapBuffers(); //implicit glFlush
}
//for the second part of program
void display_game()
{
glClearColor(0.0f, 0.0f, 0.0f, 1.0f); //Black and opaque
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
//define the projection matrix just once and use the modelview matrix all other times
glMatrixMode(GL_PROJECTION); //Applies subsequent matrix operations to the projection matrix stack
glLoadIdentity();//Reset
GLint viewport[4];
glGetIntegerv(GL_VIEWPORT, viewport); //The params parameter returns four values: the x and y window coordinates of the viewport, followed by its width and height
double aspect = (double)viewport[2] / (double)viewport[3]; // y/width would be 1.0
gluPerspective(60,aspect, 1, 100); //using perspective projection
//glOrtho(0.0f, 600.0f, 600.0f, 0.0f, 0.0f, 1.0f);
glMatrixMode(GL_MODELVIEW); //for trasformations - Applies subsequent matrix operations to the texture matrix stack
glLoadIdentity();
// move back a bit for viewer , cause of gluPerspective
glTranslatef( 0, 0, -35 );
float e=0,f=0;
glEnable(GL_TEXTURE_2D);
//construct the grid with reference the central cube
for(int i=0;i<8;i++) {
for(int j=0;j<8;j++) {
glPushMatrix();
glTranslatef(0.0f+e,0.0f+f,0.0f); //right and below
glRotatef(20.0f,1.0f,-2.0f,0.0f); //looking 3d
//glColor3ub(245, 245, 220); //Beige
//glColor3ub( rand()%255,rand()%255, rand()%255 );
myglutSolidCube(2.25);
glPopMatrix();
glPushMatrix();
glTranslatef(0.0f-e,0.0f+f,0.0f); //left and below
glRotatef(20.0f,1.0f,-2.0f,0.0f); //looking 3d
//glColor3ub( rand()%255,rand()%255, rand()%255 );
myglutSolidCube(2.25);
glPopMatrix();
glPushMatrix();
glTranslatef(0.0f+e,0.0f-f,0.0f); //right and up
glRotatef(20.0f,1.0f,-2.0f,0.0f); //looking 3d
myglutSolidCube(2.25);
glPopMatrix();
glPushMatrix();
glTranslatef(0.0f-e,0.0f-f,0.0f); //left and up
glRotatef(20.0f,1.0f,-2.0f,0.0f); //looking 3d
myglutSolidCube(2.25);
glPopMatrix();
f += -2.63;
}
f=0;
e+=2.63;
}
//SEED to some constant value for 2nd part of the program. If it is not used , cubes would change color in runtime
//srand(0x98765432);
glutSwapBuffers(); //implicit glFlush
glDisable(GL_TEXTURE_2D);
}
void reshape(GLsizei width, GLsizei height) {
// GLsizei for non-negative integer // Compute aspect ratio of the new window
if (height == 0) height = 1; // To prevent divide by 0
GLfloat aspect = (GLfloat)width / (GLfloat)height; // Set the viewport to cover the new window
glViewport(0, 0, width, height); // Set the aspect ratio of the clipping volume glMatrixMode(GL_PROJECTION); // To operate on the Projection matrix
glLoadIdentity(); // Reset // Enable perspective projection with fovy, aspect, zNear and zFar
gluPerspective(45.0f, aspect, 0.1f, 100.0f);
}
void timer(int extra)
{
glutPostRedisplay();
glutTimerFunc(16, timer, 0);
}
void mouseEscape( int button, int state, int x, int y )
{
if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN &&button==MENU_EXIT)
{
int windowID = glutCreateWindow("CUBES");
glutDestroyWindow(windowID);
exit(0);
}
glutPostRedisplay();
}
//for loading the texture
const char* filename = "salt_on_spoon.bmp";
int main(int argc, char **argv)
{
glutInit(&argc, argv);
glutInitWindowSize(600,600);
glutInitDisplayMode(GLUT_RGBA | GLUT_DEPTH | GLUT_DOUBLE| GLUT_MULTISAMPLE);
glEnable(GL_MULTISAMPLE); //anti-alliasing
glutCreateWindow("CUBES");
//create and handle the menu
my_createmenu();
glutDisplayFunc(display);
glutReshapeFunc(reshape);
glutTimerFunc(0, timer, 0);
init();
//glEnable(GL_TEXTURE_2D); //for texture
//glutMouseFunc(mouseEscape);
//glutKeyboardFunc(keyEscape);
//Load our texture
//loadTextureFromFile(filename);
glutMainLoop();
//Free our texture
//FreeTexture(texture);
return 0;
}
//create the menu-entries
void my_createmenu(void) {
// Create a menu
glutCreateMenu(menu);
// Add menu items
glutAddMenuEntry("Start Game", MENU_START);
glutAddMenuEntry("Exit", MENU_EXIT);
// Associate a mouse button with menu
glutAttachMenu(GLUT_RIGHT_BUTTON);
}
// Menu handling function-what to do in each value
void menu(int item)
{
switch (item)
{
case MENU_START: {
//glEnable(GL_TEXTURE_2D); //for texture
//Load our texture
loadTextureFromFile(filename);
glutDisplayFunc(display_game);
}
break;
case MENU_EXIT:
{
int windowID = glutCreateWindow("CUBES"); //exit game
glutDestroyWindow(windowID);
exit(0);
}
break;
default:
{ /* Nothing */ }
break;
}
glutPostRedisplay();
return;
}
I'm doing the texture loading part in the menu function. How will I be able to handle three textures? The ultimate goal is to make a rand call also for the three textures to be rendered on the cubes.
I also have two pictures: 1st: when the program begins:
2nd: after clicking "Star Game" where you can see the texture rendered in all of the cubes:
The goal is for more 2 types of textures and all of them render in random cubes.

Answer 1

You can create more than 1 texture object.
glBindTexture binds a named texture to a texturing target, that is a global state. glTexImage2D specify a two-dimensional texture image for the texture, which is currently bound to the specified target. glTexParameter set parameter to the texture object.
I recommend to write a function which loads a texture form a file to a given texture object (name id):
void loadTextureFromFile(const char *filename, unsigned int texture)
{
glBindTexture(GL_TEXTURE_2D, texture);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
// load and generate the texture
int width, height, nrChannels;
unsigned char *data = stbi_load(filename, &width, &height, &nrChannels, 0);
if (data)
{
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0,
GL_RGB, GL_UNSIGNED_BYTE, data);
//glGenerateMipmap(GL_TEXTURE_2D);
}
else
{
std::cout << "Failed to load texture" << std::endl;
}
stbi_image_free(data);
}
const char* filename1 = "salt_on_spoon.bmp";
const char* filename2 = ...;
const char* filename3 = ...;
unsigned int tob[3];
int main(int argc, char **argv)
{
// [...]
glGenTextures(3, &tob[0]);
loadTextureFromFile(filename1, tob[0]);
loadTextureFromFile(filename2, tob[1]);
loadTextureFromFile(filename3, tob[2]);
// [...]
}
When two-dimensional texturing is enabled, then the image of the texture object, which is currently bound to the target GL_TEXTURE_2D is wrapped on the mesh.
You've to bind the proper texture object, before you draw the geometry. e.g:
for(int i=0;i<8;i++) {
for(int j=0;j<8;j++) {
glBindTexture(GL_TEXTURE_2D, tob[0]);
glPushMatrix();
glTranslatef(0.0f+e,0.0f+f,0.0f); //right and below
glRotatef(20.0f,1.0f,-2.0f,0.0f); //looking 3d
myglutSolidCube(2.25);
glPopMatrix();
glBindTexture(GL_TEXTURE_2D, tob[1]);
glPushMatrix();
glTranslatef(0.0f-e,0.0f+f,0.0f); //left and below
glRotatef(20.0f,1.0f,-2.0f,0.0f); //looking 3d
myglutSolidCube(2.25);
glPopMatrix();
glBindTexture(GL_TEXTURE_2D, tob[2]);
glPushMatrix();
glTranslatef(0.0f+e,0.0f-f,0.0f); //right and up
glRotatef(20.0f,1.0f,-2.0f,0.0f); //looking 3d
myglutSolidCube(2.25);
glPopMatrix();
glBindTexture(GL_TEXTURE_2D, tob[0]);
glPushMatrix();
glTranslatef(0.0f-e,0.0f-f,0.0f); //left and up
glRotatef(20.0f,1.0f,-2.0f,0.0f); //looking 3d
myglutSolidCube(2.25);
glPopMatrix();
f += -2.63;
}
f=0;
e+=2.63;
}
Note, the distribution of the textures is just an example. You've to ensure that unsigned int tob[3]; is declared before, in global namespace.