FramebuffersGL 3.0

glFramebufferTexture2D

Attaches a 2D texture to the bound framebuffer so rendering writes into it.

Signature

void glFramebufferTexture2D(GLenum target, GLenum attachment,
                            GLenum textarget, GLuint texture, GLint level);

How it works

Plugs a texture into one attachment slot of the FBO. Afterwards, drawing writes into the texture, and later you can sample that same texture in a shader. Use this when you need to READ the result (color for post-processing, depth for shadow maps). If you never read it, a renderbuffer is enough.

Parameters

targetGLenum

GL_FRAMEBUFFER (or DRAW/READ variant).

attachmentGLenum

Which slot.

Common values

GL_COLOR_ATTACHMENT0 … n: Color outputs. The fragment shader's out variables write here (location 0 → attachment 0).
GL_DEPTH_ATTACHMENT: Depth buffer.
GL_STENCIL_ATTACHMENT: Stencil buffer.
GL_DEPTH_STENCIL_ATTACHMENT: Combined depth + stencil (e.g. GL_DEPTH24_STENCIL8).

textargetGLenum

GL_TEXTURE_2D, or a cube face GL_TEXTURE_CUBE_MAP_POSITIVE_X + i.

textureGLuint

The texture (already allocated with the right format).

levelGLint

Mip level to render into, usually 0.

Tips & pitfalls

Never sample a texture while it is attached to the FBO you are drawing into — the result is undefined (feedback loop).

Errors

When the call is invalid it does nothing and sets an error, which glGetError returns:

GL_INVALID_OPERATION: Framebuffer 0 is bound, or textarget does not match the texture type.

Example

example.cpp

1GLuint color;
2glGenTextures(1, &color);
3glBindTexture(GL_TEXTURE_2D, color);
4glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA16F, w, h, 0, GL_RGBA, GL_FLOAT, nullptr);
5glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
6
7glBindFramebuffer(GL_FRAMEBUFFER, fbo);
8glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, color, 0);

Official Khronos documentation