OpenGL displays the texture of all white

Question

I am trying to make a .png image as a texture. However, all that is displayed is a white square.

I give my texture a unique int identifier, called texID, that reads pixeldata into the buffer image (declared in the .h file). I load my pixelbuffer, do all my OpenGL stuff and bind this pixelbuffer to a texture for OpenGL. Then I draw everything using glDrawElements.

I also initialize a 32x32 texture when I call its constructor, so I doubt that it is related to the power of the two-size problem.

Can anyone see errors in my OpenGL installation GL_TEXTURE_2D that can give me a white square block.

#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 POT unsigned error = lodepng::decode(image,w,h,fnPtr);//lodepng 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 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 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 will also include the main init 'init, where I will install OGL a bit 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 to the main function, where I first installed the 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, the usual checklist for any texture looks white:

• Is the OpenGL context created and tied to the current thread when loading the texture?

• Highlighted texture id using glGenTextures ?

• Are the format and internal format to glTex[Sub]Image… parameters valid OpenGL tokens as input to this function?

• Is mipmapping used?

  • YES: Set 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: disable mipmap filtering by setting glTexParameteri GL_TEXTURE_MIN_FILTER to GL_NEAREST or GL_LINEAR.