Why texture mapping dose not work? - opengl

Question

#include <Windows.h>
#include "glut.h"
#include "GLAUX.H"
#include <stdio.h>
GLuint texID;
void display()
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glClearColor(0,0,0,0);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LESS);
glMatrixMode(GL_TEXTURE);
glLoadIdentity();
gluLookAt(10,10,10,0,0,0,0,0,1);
glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D,texID);
glColor3f(0.9f,0.9f,0.9f);
glBegin(GL_QUADS);
glTexCoord2f(0.f,0.f);
glVertex3f(-100.0f, 0.0f, -100.0f);
glTexCoord2f(0.f,1.f);
glVertex3f(-100.0f,0.0f,100.0f);
glTexCoord2f(1.f,1.f);
glVertex3f(100.0f,0.0f,100.0f);
glTexCoord2f(1.f,0.f);
glVertex3f(100.0f, 0.0f, -100.0f);
glEnd();
glutSwapBuffers();
}
void InitTexture()
{
glGenTextures(1,&texID);
AUX_RGBImageRec * image = auxDIBImageLoad("earth.bmp");
if(!image)
puts("image open err\n");
glBindTexture(GL_TEXTURE_2D, texID);
// glTexImage2D(GL_TEXTURE_2D, 0, 3, image->sizeX,image->sizeY,0,GL_RGB,GL_UNSIGNED_BYTE,
// image->data);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
gluBuild2DMipmaps(GL_TEXTURE_2D, 3, image->sizeX, image->sizeY, GL_RGB, GL_UNSIGNED_BYTE,image->data);
delete image->data;
delete image;
image = NULL;
}
void reshape (int w, int h) {
float ratio = w/(float)h;
glViewport(0,0,w,h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45,ratio,10,1000);
}
int main(int argc, char** argv)
{
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGBA|GLUT_DEPTH);
glutInitWindowSize(500,500);
glutCreateWindow("3D FORTRESS");
InitTexture();
glClear(GL_COLOR_BUFFER_BIT);
glutDisplayFunc(display);
glutIdleFunc (display);
glutReshapeFunc (reshape);
glutMainLoop();
return 0;
}
i'm trying to make a simple texture mapping..
but it doesn't work at all. it just displays black screen. though It reads bmp files well...

Answer 1

Several things wrong with this code:
glClearColor after glClear does not have any effect (until the next time through the display function).
You are switching to the texture matrix with glMatrixMode(GL_TEXTURE); but then load a view matrix into it. If you're just getting started with OpenGL, the texture matrix is not something you should be using; this should probably be GL_MODELVIEW.
The first argument to gluBuild2DMipmaps must be GLU_TEXTURE_2D.
You're not checking the return value of gluBuild2DMipmaps.
You're not checking for any OpenGL errors. Use glGetError() to pinpoint the source of any problems.
In general, with problems like this, narrow it down by commenting out features first. Here, I'd start with drawing a coloured quad without any texture, then add the texture to it.