diff --git a/comfy_extras/nodes_eps.py b/comfy_extras/nodes_eps.py new file mode 100644 index 000000000000..c8818f096d9b --- /dev/null +++ b/comfy_extras/nodes_eps.py @@ -0,0 +1,60 @@ +class EpsilonScaling: + """ + Implements the Epsilon Scaling method from 'Elucidating the Exposure Bias in Diffusion Models' + (https://arxiv.org/abs/2308.15321v6). + + This method mitigates exposure bias by scaling the predicted noise during sampling, + which can significantly improve sample quality. This implementation uses the "uniform schedule" + recommended by the paper for its practicality and effectiveness. + """ + @classmethod + def INPUT_TYPES(s): + return { + "required": { + "model": ("MODEL",), + "scaling_factor": ("FLOAT", { + "default": 1.005, + "min": 0.5, + "max": 1.5, + "step": 0.001, + "display": "number" + }), + } + } + + RETURN_TYPES = ("MODEL",) + FUNCTION = "patch" + + CATEGORY = "model_patches/unet" + + def patch(self, model, scaling_factor): + # Prevent division by zero, though the UI's min value should prevent this. + if scaling_factor == 0: + scaling_factor = 1e-9 + + def epsilon_scaling_function(args): + """ + This function is applied after the CFG guidance has been calculated. + It recalculates the denoised latent by scaling the predicted noise. + """ + denoised = args["denoised"] + x = args["input"] + + noise_pred = x - denoised + + scaled_noise_pred = noise_pred / scaling_factor + + new_denoised = x - scaled_noise_pred + + return new_denoised + + # Clone the model patcher to avoid modifying the original model in place + model_clone = model.clone() + + model_clone.set_model_sampler_post_cfg_function(epsilon_scaling_function) + + return (model_clone,) + +NODE_CLASS_MAPPINGS = { + "Epsilon Scaling": EpsilonScaling +} diff --git a/nodes.py b/nodes.py index 1a6784b686bc..88d7129938e5 100644 --- a/nodes.py +++ b/nodes.py @@ -2297,6 +2297,7 @@ async def init_builtin_extra_nodes(): "nodes_gits.py", "nodes_controlnet.py", "nodes_hunyuan.py", + "nodes_eps.py", "nodes_flux.py", "nodes_lora_extract.py", "nodes_torch_compile.py",