What causes "Framebuffer is not complete" in Comfy-Org/ComfyUI?

Reduce the number of outputs of the GLSL node (split the effect across two nodes/stages).

Comfy-Org/ComfyUI · error · RuntimeError

Framebuffer is not complete

Error message

Framebuffer is not complete

What it means

Raised in _render_shader_batch() after attaching one RGBA32F texture per output to the FBO and calling glDrawBuffers() with all color attachments; glCheckFramebufferStatus() did not report GL_FRAMEBUFFER_COMPLETE. With MRT of float textures the two usual causes are: num_outputs exceeding GL_MAX_COLOR_ATTACHMENTS, or the driver not treating RGBA32F as color-renderable without EXT_color_buffer_float.

Source

Thrown at comfy_extras/nodes_glsl.py:474

        # Create framebuffer with only the needed color attachments
        fbo = gl.glGenFramebuffers(1)
        gl.glBindFramebuffer(gl.GL_FRAMEBUFFER, fbo)

        draw_buffers = []
        for i in range(num_outputs):
            tex = gl.glGenTextures(1)
            output_textures.append(tex)
            gl.glBindTexture(gl.GL_TEXTURE_2D, tex)
            gl.glTexImage2D(gl.GL_TEXTURE_2D, 0, gl.GL_RGBA32F, width, height, 0, gl.GL_RGBA, gl.GL_FLOAT, None)
            gl.glTexParameteri(gl.GL_TEXTURE_2D, gl.GL_TEXTURE_MIN_FILTER, gl.GL_LINEAR)
            gl.glTexParameteri(gl.GL_TEXTURE_2D, gl.GL_TEXTURE_MAG_FILTER, gl.GL_LINEAR)
            gl.glFramebufferTexture2D(gl.GL_FRAMEBUFFER, gl.GL_COLOR_ATTACHMENT0 + i, gl.GL_TEXTURE_2D, tex, 0)
            draw_buffers.append(gl.GL_COLOR_ATTACHMENT0 + i)

        gl.glDrawBuffers(num_outputs, draw_buffers)

        if gl.glCheckFramebufferStatus(gl.GL_FRAMEBUFFER) != gl.GL_FRAMEBUFFER_COMPLETE:
            raise RuntimeError("Framebuffer is not complete")

        # Create ping-pong resources for multi-pass rendering
        if num_passes > 1:
            for _ in range(2):
                pp_tex = gl.glGenTextures(1)
                ping_pong_textures.append(pp_tex)
                gl.glBindTexture(gl.GL_TEXTURE_2D, pp_tex)
                gl.glTexImage2D(gl.GL_TEXTURE_2D, 0, gl.GL_RGBA32F, width, height, 0, gl.GL_RGBA, gl.GL_FLOAT, None)
                gl.glTexParameteri(gl.GL_TEXTURE_2D, gl.GL_TEXTURE_MIN_FILTER, gl.GL_LINEAR)
                gl.glTexParameteri(gl.GL_TEXTURE_2D, gl.GL_TEXTURE_MAG_FILTER, gl.GL_LINEAR)
                gl.glTexParameteri(gl.GL_TEXTURE_2D, gl.GL_TEXTURE_WRAP_S, gl.GL_CLAMP_TO_EDGE)
                gl.glTexParameteri(gl.GL_TEXTURE_2D, gl.GL_TEXTURE_WRAP_T, gl.GL_CLAMP_TO_EDGE)

                pp_fbo = gl.glGenFramebuffers(1)
                ping_pong_fbos.append(pp_fbo)
                gl.glBindFramebuffer(gl.GL_FRAMEBUFFER, pp_fbo)
                gl.glFramebufferTexture2D(gl.GL_FRAMEBUFFER, gl.GL_COLOR_ATTACHMENT0, gl.GL_TEXTURE_2D, pp_tex, 0)
                gl.glDrawBuffers(1, [gl.GL_COLOR_ATTACHMENT0])

View on GitHub (pinned to 1c6d8d45b3)

Solutions

Reduce the number of outputs of the GLSL node (split the effect across two nodes/stages).
Verify EXT_color_buffer_float is present (glGetString(GL_EXTENSIONS) / the log line printed at context init); if absent, update drivers or use a GPU/driver stack that exposes it.
Confirm width and height are > 0 and within GL_MAX_TEXTURE_SIZE.
On software rendering, switch to a real GPU or accept fewer outputs.

Defensive patterns

Strategy: validation

Validate before calling

# Before configuring many outputs, check the driver limit (needs a live GL context):
# max_attachments = gl.glGetIntegerv(gl.GL_MAX_COLOR_ATTACHMENTS)
# assert num_outputs <= max_attachments
# assert 'EXT_color_buffer_float' in gl.glGetString(gl.GL_EXTENSIONS)
num_outputs = 4  # keep conservative; most drivers guarantee >= 4

Try / catch

try:
    out = run_glsl(...)
except RuntimeError as e:
    if "Framebuffer is not complete" in str(e):
        raise ValueError("Reduce the node's output count or use a driver with EXT_color_buffer_float") from e
    raise

Prevention

Keep MRT output counts small (<= 4) for portability.
Confirm EXT_color_buffer_float is listed in the context init log line before relying on float outputs.
Avoid 0-sized width/height inputs.

When it happens

Trigger: A GLSL node configured with more outputs than the implementation supports (software/older drivers commonly cap at 4-8 color attachments); GLES3.0 contexts lacking EXT_color_buffer_float where rendering to GL_RGBA32F is illegal; width/height of 0.

Common situations: Requesting 8-16 outputs from one fragment shader on Mesa llvmpipe or embedded drivers; running on a GLES3 context where only half-float rendering is guaranteed.

Related errors

AI-assisted analysis of Comfy-Org/ComfyUI@1c6d8d45b3 (2026-08-14). Data as JSON: /api/errors/4182837dd1f0158a. Report an issue: GitHub.