I am trying to map a simple texture onto a quad, its all loaded in fine but it displays at a dogi angle, which im pretty sure is because i have done the glTexCoord2f() coordinates incorrectly.
Heres my code:
glBegin(GL_QUADS);
glTexCoord2f(0.0,1.0); glVertex2f(-100, 100); // top left
glTexCoord2f(1.0,1.0); glVertex2f(100, 100); // top right
glTexCoord2f(1.0,0.0); glVertex2f(100, -100); // bottom right
glTexCoord2f(0.0,0.0); glVertex2f(-100, -100); // bottom left
glEnd();
This is how it looks (the rendered quad on the left, and the actual texture on the right):
Thanks for the reply, im using NeHes bitmap loader, specifically this code:
int LoadGLTextures() // Load Bitmaps And Convert To Textures
{
int Status=FALSE; // Status Indicator
AUX_RGBImageRec *TextureImage[1]; // Create Storage Space For The Texture
memset(TextureImage,0,sizeof(void *)*1); // Set The Pointer To NULL
// Load The Bitmap, Check For Errors, If Bitmap's Not Found Quit
if (TextureImage[0]=LoadBMP("C:\\Users\\Jack\\Desktop\\SpaceInvader\\Data\\invader_texture.bmp"))
{
Status=TRUE; // Set The Status To TRUE
glGenTextures(1, &texture[0]); // Create The Texture
// Typical Texture Generation Using Data From The Bitmap
glBindTexture(GL_TEXTURE_2D, texture[0]);
glTexImage2D(GL_TEXTURE_2D, 0, 3, TextureImage[0]->sizeX, TextureImage[0]->sizeY, 0, GL_RGB, GL_UNSIGNED_BYTE, TextureImage[0]->data);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S,
GL_REPEAT);
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T,
GL_REPEAT);
}
if (TextureImage[0]) // If Texture Exists
{
if (TextureImage[0]->data) // If Texture Image Exists
{
free(TextureImage[0]->data); // Free The Texture Image Memory
}
free(TextureImage[0]); // Free The Image Structure
}
return Status; // Return The Status
}
The code detects the width and height of the texture correctly when glTexImage2D() is called so i dont think thats the problem?
I simply use the LoadGLTextures() function, then enable and bind the texture.
glTexImage2D seems to read one pixel too much per line, as each line is shifted one more pixel to the left (from bottom to top) and the right half of the topmost line is filled with random pixels.
Could you try to TextureImage[0]->sizeX - 1 as width?
AUX_RGBImageRec *LoadBMP(char *Filename) // Loads A Bitmap Image
{
FILE *File=NULL; // File Handle
if (!Filename) // Make Sure A Filename Was Given
{
return NULL; // If Not Return NULL
}
File=fopen(Filename,"r"); // Check To See If The File Exists
if (File) // Does The File Exist?
{
fclose(File); // Close The Handle
return auxDIBImageLoad(Filename); // Load The Bitmap And Return A Pointer
}
return NULL; // If Load Failed Return NULL
}
The returned data is then used by the LoadGLTextures() function i posted above.
glTexImage2D seems to read one pixel too much per line, as each line is shifted one more pixel to the left (from bottom to top) and the right half of the topmost line is filled with random pixels.
Could you try to TextureImage[0]->sizeX - 1 as width?[/QUOTE]
I’ve seen some nasty padding/alignment nonsense in BMP loaders.
Make sure the BMP is 2^n wide, or at least that is not an odd number of pixels wide. You may have found a bug in that aux lib code. It’s a deprecated library now although tutorials like NeHe still use it.
Hmm, given your last post it might be a driver issue although you’re definitely relying on non power of two textures now and I doubt you’ve tested for the extension.
Thanks very much for the help guys, turns out i made a stupid mistake and the bitmaps width/height were not powers of two :sorrow: , which caused the pixel mess up, Oh well i wont be making that mistake again!
bmp files are typically (always?) aligned on 4 bytes per row, which means 24bit images often have extra bytes at the end of each row. With POT textures this will not be a problem unless it’s smaller than 4 pixels wide.
