glTexCoordPointer

glTexCoordPointer is a legacy OpenGL function that specifies the location and data format of texture coordinate data used when rendering with vertex arrays. It defines how many components per texture coordinate (size), the data type of each component, the stride between consecutive coordinates, and the pointer to the first coordinate in memory. The coordinates feed the currently enabled texture coordinate array, accessed via GL_TEXTURE_COORD_ARRAY.

Parameters and usage:

- size: 2, 3, or 4, corresponding to the dimensionality of the texture coordinates.

- type: the data type of each component (for example GL_FLOAT, GL_SHORT, GL_DOUBLE, etc.).

- stride: the byte offset between consecutive texture coordinates. A value of 0 indicates tightly packed data.

- pointer: the address of the first coordinate in memory. When using vertex buffer objects (VBOs), this is treated as an offset within the buffer.

Before using glTexCoordPointer, the texture coordinate array must be enabled with glEnableClientState(GL_TEXTURE_COORD_ARRAY). In multi-texture setups, you select the active texture unit with glClientActiveTexture(GL_TEXTURE0 + unit) and then call glTexCoordPointer to define the coordinates for that unit.

Data can be interleaved with other vertex data or stored in separate arrays. The stride and pointer parameters allow flexible data layouts, including interleaved arrays and VBO-based storage. The function is part of the fixed-function pipeline and works alongside glVertexPointer, glNormalPointer, and glColorPointer.

In modern OpenGL, glTexCoordPointer is deprecated in favor of using generic vertex attributes (glVertexAttribPointer) and shaders. Texture coordinates are then read in the shader via a dedicated input attribute, typically bound to a sampler in the fragment shader.

Common issues include mismatched size and data, incorrect type enum, or forgetting to enable the texture coordinate array, which can lead to missing textures or rendering artifacts.