Textures

Tags: opengl

A texture is an image that opengl can load and apply onto a surface at runtime.

Different image formats need to be loaded seperately. Writing an image loader for all of these is too time consuming to be practical so we use pre-made libraries for this. The stb_image library is a common choice. We can load an image like so:

int width, height, nrChannels;
unsigned char *data = stbi_load("container.jpg", &width, &height, &nrChannels, 0);

// free with `stbi_image_free(data)`.

Loading a texture

First we create an ID to reference the texture on the GPU.

unsigned int texture;
glGenTextures(1, &texture);
// let's also go ahead and bind it now.
glBindTexture(GL_TEXTURE_2D, texture);

Then we assign the texture data

glTexImage2D(
  GL_TEXTURE_2D,    // Specify the texture target. Each bound texture has space for 1D, 2D and 3D. Assigning a 2D texture doesn't overwrite any existing 1D/3D texture.
  0,                // mipmap level, in-case we want to assign it manually.
  GL_RGB,           // The kind of format we'll store the texture in.
  width,            // The width of the texture being loaded.
  height,           // The height of the texture being loaded.
  0,                // don't care... just always make it 0. *legacy stuff*
  GL_RGB,           // The format of the texture data we're loading from.
  GL_UNSIGNED_BYTE, // The datatype of the texture data we're loading from.
  data              // Texture data to load.
);

We can also optionally declare it as a mipmap.

glGenerateMipmap(GL_TEXTURE_2D);

Links to this note

Texture Unit