Direct State AccessGL 4.5

glNamedFramebufferDrawBuffers

Lists which colour attachments the fragment shader's outputs go to (multiple render targets).

Signature

void glNamedFramebufferDrawBuffers(GLuint framebuffer, GLsizei n, const GLenum *bufs);

How it works

A fragment shader can write several outputs: layout(location = 0) out vec4 accum; layout(location = 1) out float reveal;. This list connects output location i to bufs[i]. By default only GL_COLOR_ATTACHMENT0 is enabled, so a second output is silently dropped until you list both.

It is a setting of the framebuffer, so set it once after attaching, not every frame.

Parameters

framebufferGLuint

The framebuffer (0 = the window, which takes GL_BACK_LEFT and similar).

nGLsizei

Number of entries, up to GL_MAX_DRAW_BUFFERS (at least 8).

bufsconst GLenum *

GL_COLOR_ATTACHMENTi or GL_NONE for each output location.

Tips & pitfalls

  • Direct State Access (GL 4.5): the object is passed as a parameter, so nothing needs to be bound and no global state is disturbed.

Errors

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

GL_INVALID_VALUE
n is larger than GL_MAX_DRAW_BUFFERS.
GL_INVALID_OPERATION
The same attachment appears twice.

Example

example.cpp
1GLenum bufs[] = { GL_COLOR_ATTACHMENT0, GL_COLOR_ATTACHMENT1 };
2glNamedFramebufferDrawBuffers(oitFbo, 2, bufs);

Related

glDrawBuffersConnects the fragment shader's outputs to colour attachments of the bound framebuffer (multiple render targets).glBlendFunciglBlendFunc for one colour attachment only, when a shader writes to several at once.glNamedFramebufferTextureAttaches a texture to a framebuffer, so drawing into the framebuffer writes into the texture.glClearNamedFramebufferfvClears one attachment of a framebuffer to a value of your choice, without glClearColor.
Official Khronos documentation