OpenGL renders texture all white - c++

Question

I'm attempting to render a .png image as a texture. However, all that is being rendered is a white square.
I give my texture a unique int ID called texID, read the pixeldata into a buffer 'image' (declared in the .h file). I load my pixelbuffer, do all of my OpenGL stuff and bind that pixelbuffer to a texture for OpenGL. I then draw it all using glDrawElements.
Also I initialize the texture with a size of 32x32 when its contructor is called, therefore i doubt it is related to a power of two size issue.
Can anybody see any mistakes in my OpenGL GL_TEXTURE_2D setup that might give me a block white square.
#include "Texture.h"
Texture::Texture(int width, int height, string filename)
{
const char* fnPtr = filename.c_str(); //our image loader accepts a ptr to a char, not a string
printf(fnPtr);
w = width; //give our texture a width and height, the reason that we need to pass in the width and height values manually
h = height;//UPDATE, these MUST be P.O.T.
unsigned error = lodepng::decode(image,w,h,fnPtr);//lodepng's decode function will load the pixel data into image vector
//display any errors with the texture
if(error)
{
cout << "\ndecoder error " << error << ": " << lodepng_error_text(error) <<endl;
}
for(int i = 0; i<image.size(); i++)
{
printf("%i,", image.at(i));
}
printf("\nImage size is %i", image.size());
//image now contains our pixeldata. All ready for OpenGL to do its thing
//let's get this texture up in the video memory
texGLInit();
}
void Texture::texGLInit()
{
//WHERE YOU LEFT OFF: glGenTextures isn't assigning an ID to textures. it stays at zero the whole time
//i believe this is why it's been rendering white
glGenTextures(1, &textures);
printf("\ntexture = %u", textures);
glBindTexture(GL_TEXTURE_2D, textures);//evrything we're about to do is about this texture
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
//glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
//glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
//glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
//glDisable(GL_COLOR_MATERIAL);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8,w,h,0, GL_RGBA, GL_UNSIGNED_BYTE, &image);
//we COULD free the image vectors memory right about now.
}
void Texture::draw(point centerPoint, point dimensions)
{
glEnable(GL_TEXTURE_2D);
printf("\nDrawing block at (%f, %f)",centerPoint.x, centerPoint.y);
glBindTexture(GL_TEXTURE_2D, textures);//bind the texture
//create a quick vertex array for the primitive we're going to bind the texture to
printf("TexID = %u",textures);
GLfloat vArray[8] =
{
centerPoint.x-(dimensions.x/2), centerPoint.y-(dimensions.y/2),//bottom left i0
centerPoint.x-(dimensions.x/2), centerPoint.y+(dimensions.y/2),//top left i1
centerPoint.x+(dimensions.x/2), centerPoint.y+(dimensions.y/2),//top right i2
centerPoint.x+(dimensions.x/2), centerPoint.y-(dimensions.y/2)//bottom right i3
};
//create a quick texture array (we COULD create this on the heap rather than creating/destoying every cycle)
GLfloat tArray[8] =
{
0.0f,0.0f, //0
0.0f,1.0f, //1
1.0f,1.0f, //2
1.0f,0.0f //3
};
//and finally.. the index array...remember, we draw in triangles....(and we'll go CW)
GLubyte iArray[6] =
{
0,1,2,
0,2,3
};
//Activate arrays
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
//Give openGL a pointer to our vArray and tArray
glVertexPointer(2, GL_FLOAT, 0, &vArray[0]);
glTexCoordPointer(2, GL_FLOAT, 0, &tArray[0]);
//Draw it all
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_BYTE, &iArray[0]);
//glDrawArrays(GL_TRIANGLES,0,6);
//Disable the vertex arrays
glDisableClientState(GL_VERTEX_ARRAY);
glDisableClientState(GL_TEXTURE_COORD_ARRAY);
glDisable(GL_TEXTURE_2D);
//done!
/*glBegin(GL_QUADS);
glTexCoord2f(0.0f,0.0f);
glVertex2f(centerPoint.x-(dimensions.x/2), centerPoint.y-(dimensions.y/2));
glTexCoord2f(0.0f,1.0f);
glVertex2f(centerPoint.x-(dimensions.x/2), centerPoint.y+(dimensions.y/2));
glTexCoord2f(1.0f,1.0f);
glVertex2f(centerPoint.x+(dimensions.x/2), centerPoint.y+(dimensions.y/2));
glTexCoord2f(1.0f,0.0f);
glVertex2f(centerPoint.x+(dimensions.x/2), centerPoint.y-(dimensions.y/2));
glEnd();*/
}
Texture::Texture(void)
{
}
Texture::~Texture(void)
{
}
I'll also include the main class' init, where I do a bit more OGL setup before this.
void init(void)
{
printf("\n......Hello Guy. \n....\nInitilising");
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0,XSize,0,YSize);
glEnable(GL_TEXTURE_2D);
myBlock = new Block(0,0,offset);
glClearColor(0,0.4,0.7,1);
glLineWidth(2); // Width of the drawing line
glMatrixMode(GL_MODELVIEW);
glDisable(GL_DEPTH_TEST);
printf("\nInitialisation Complete");
}
Update: adding in the main function where I first setup my OpenGL window.
int main(int argc, char** argv)
{
glutInit(&argc, argv); // GLUT Initialization
glutInitDisplayMode(GLUT_RGBA|GLUT_DOUBLE); // Initializing the Display mode
glutInitWindowSize(800,600); // Define the window size
glutCreateWindow("Gem Miners"); // Create the window, with caption.
printf("\n========== McLeanTech Systems =========\nBecoming Sentient\n...\n...\n....\nKILL\nHUMAN\nRACE \n");
init(); // All OpenGL initialization
//-- Callback functions ---------------------
glutDisplayFunc(display);
glutKeyboardFunc(mykey);
glutSpecialFunc(processSpecialKeys);
glutSpecialUpFunc(processSpecialUpKeys);
//glutMouseFunc(mymouse);
glutMainLoop(); // Loop waiting for event
}

Answer 1

Here's the usual checklist for whenever textures come out white:
OpenGL context created and being bound to current thread when attemting to load texture?
Allocated texture ID using glGenTextures?
Are the parameters format and internal format to glTex[Sub]Image… valid OpenGL tokens allowed as input for this function?
Is mipmapping being used?
YES: Supply all mipmap layers – optimally set glTexParameteri GL_TEXTURE_BASE_LEVEL and GL_TEXTURE_MAX_LEVEL, as well as GL_TEXTURE_MIN_LOD and GL_TEXTURE_MAX_LOG.
NO: Turn off mipmap filtering by setting glTexParameteri GL_TEXTURE_MIN_FILTER to GL_NEAREST or GL_LINEAR.