Function familiesfamily

glTexSubImage*

Overwrite part of an existing texture; the number is the texture's dimensions, Texture instead of Tex means DSA.

Signature

void glTexSubImage{1D|2D|3D}(GLenum target, GLint level, offsets…, sizes…, GLenum format, GLenum type, const void *pixels);
void glTextureSubImage{1D|2D|3D}(GLuint texture, …);
void glCompressedTextureSubImage{1D|2D|3D}(GLuint texture, …, GLsizei imageSize, const void *data);

How it works

All of them write pixels into storage that already exists, without reallocating. They differ in three ways that can be read from the name: 1D / 2D / 3D gives the number of offsets and sizes (a texture array counts as 3D, the layer being the third coordinate); glTexture… takes the texture ID instead of a bound target; Compressed… takes ready-made compressed blocks with their byte size instead of format and type.

Reading the name

1D / 2D / 3D
Dimensions: x; x, y; or x, y, z (or layer).
Tex / Texture
Bound target (classic) / texture ID (DSA, GL 4.5).
Compressed
Pre-compressed blocks (BC7, ASTC…).

Functions in this family

glTexSubImage2DOverwrites a rectangle of an existing texture's pixels, without reallocating it.glTextureSubImage2DUploads pixels into a region of an existing texture by ID.glCompressedTextureSubImage2DUploads already-compressed blocks (BC7, BC1, ASTC…) into one mip level of a texture.

Example

example.cpp
1glTexSubImage2D(GL_TEXTURE_2D, 0, x, y, w, h, GL_RGBA, GL_UNSIGNED_BYTE, pixels);
2glTextureSubImage2D(tex, 0, x, y, w, h, GL_RGBA, GL_UNSIGNED_BYTE, pixels);   // same, by ID

Related

glTexImage2DAllocates a 2D texture image and optionally uploads pixels into it.glTexStorage2DAllocates immutable storage for all mip levels of a 2D texture at once.glPixelStoreiTells OpenGL how pixel rows are laid out in your memory, for uploads (unpack) and readbacks (pack).