Texture mapping in OpenGL (with SOIL) - c

Question

I'm having trouble getting a texture loaded with SOIL to show up properly on this quad. In case it's not clear, I'm just writing up a little 2D sprite engine, and this is the rendering portion (needs a bit of optimization without a doubt). I haven't done any OpenGL in a couple months, and I'm admittedly quite rusty.
#include <OpenGL/OpenGL.h>
#include <GLUT/GLUT.h>
#include "SOIL.h"
#include <stdio.h>
GLuint linktex;
void drawSprite(GLint left, GLint right, GLint bottom, GLint top, GLuint texture){
//Draw clockwise
glColor3f(1.0, 1.0, 1.0);
glBindTexture(GL_TEXTURE_2D, texture);
glBegin(GL_QUADS);
glTexCoord2i(1,1); glVertex2i(right , top);
glTexCoord2i(1,0); glVertex2i(right , bottom);
glTexCoord2i(0,0); glVertex2i(left , bottom);
glTexCoord2i(0,1); glVertex2i(left , top);
glEnd();
}
void display(void){
glClearColor(0.0, 0.0, 0.0, 1.0);
glClear(GL_COLOR_BUFFER_BIT);
glLoadIdentity();
glOrtho(0.0, 240.0, 0.0, 160.0, -1.0, 1.0);
drawSprite(50, 82, 50, 82, linktex);
glFlush();
}
void reshape(int w, int h){
glViewport(0, 0, (GLsizei)w, (GLsizei)h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glMatrixMode(GL_MODELVIEW);
}
void init(){
glEnable(GL_TEXTURE_2D);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glFrontFace(GL_CW);
GLuint linktex = SOIL_load_OGL_texture(
"link.png",
SOIL_LOAD_AUTO,
SOIL_CREATE_NEW_ID,
SOIL_FLAG_INVERT_Y
);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR_MIPMAP_LINEAR);
if( 0 == linktex )
{
printf( "SOIL loading error: '%s'\n", SOIL_last_result());
}
}
int main (int argc, char **argv) {
glutInit (&argc, argv);
glutInitDisplayMode (GLUT_SINGLE);
glutInitWindowSize (240, 160);
glutInitWindowPosition (100, 100);
glutCreateWindow ("Test");
glutDisplayFunc (display);
glutReshapeFunc (reshape);
glutMainLoop();
init();
return 0;
}

Answer 1

It looks like when you are loading the texture, you are assigning the id to a local variable linktex instead of the global you declared at the beginning of the file.
When you reference linktex in the void display(void); method, the texture is un-initialized.
Try changing your call to load the texture to :
// comment out the type declaration, to assign to the global instead of a local
/*GLuint*/ linktex = SOIL_load_OGL_texture(
"link.png",
SOIL_LOAD_AUTO,
SOIL_CREATE_NEW_ID,
SOIL_FLAG_INVERT_Y
);