Add TCFG node (#8730)

Author: chaObserv

comfy_extras/nodes_tcfg.py

@@ -0,0 +1,71 @@
+# TCFG: Tangential Damping Classifier-free Guidance - (arXiv: https://arxiv.org/abs/2503.18137)
+
+import torch
+
+from comfy.comfy_types import IO, ComfyNodeABC, InputTypeDict
+
+
+def score_tangential_damping(cond_score: torch.Tensor, uncond_score: torch.Tensor) -> torch.Tensor:
+    """Drop tangential components from uncond score to align with cond score."""
+    # (B, 1, ...)
+    batch_num = cond_score.shape[0]
+    cond_score_flat = cond_score.reshape(batch_num, 1, -1).float()
+    uncond_score_flat = uncond_score.reshape(batch_num, 1, -1).float()
+
+    # Score matrix A (B, 2, ...)
+    score_matrix = torch.cat((uncond_score_flat, cond_score_flat), dim=1)
+    try:
+        _, _, Vh = torch.linalg.svd(score_matrix, full_matrices=False)
+    except RuntimeError:
+        # Fallback to CPU
+        _, _, Vh = torch.linalg.svd(score_matrix.cpu(), full_matrices=False)
+
+    # Drop the tangential components
+    v1 = Vh[:, 0:1, :].to(uncond_score_flat.device)  # (B, 1, ...)
+    uncond_score_td = (uncond_score_flat @ v1.transpose(-2, -1)) * v1
+    return uncond_score_td.reshape_as(uncond_score).to(uncond_score.dtype)
+
+
+class TCFG(ComfyNodeABC):
+    @classmethod
+    def INPUT_TYPES(cls) -> InputTypeDict:
+        return {
+            "required": {
+                "model": (IO.MODEL, {}),
+            }
+        }
+
+    RETURN_TYPES = (IO.MODEL,)
+    RETURN_NAMES = ("patched_model",)
+    FUNCTION = "patch"
+
+    CATEGORY = "advanced/guidance"
+    DESCRIPTION = "TCFG – Tangential Damping CFG (2503.18137)\n\nRefine the uncond (negative) to align with the cond (positive) for improving quality."
+
+    def patch(self, model):
+        m = model.clone()
+
+        def tangential_damping_cfg(args):
+            #  Assume [cond, uncond, ...]
+            x = args["input"]
+            conds_out = args["conds_out"]
+            if len(conds_out) <= 1 or None in args["conds"][:2]:
+                # Skip when either cond or uncond is None
+                return conds_out
+            cond_pred = conds_out[0]
+            uncond_pred = conds_out[1]
+            uncond_td = score_tangential_damping(x - cond_pred, x - uncond_pred)
+            uncond_pred_td = x - uncond_td
+            return [cond_pred, uncond_pred_td] + conds_out[2:]
+
+        m.set_model_sampler_pre_cfg_function(tangential_damping_cfg)
+        return (m,)
+
+
+NODE_CLASS_MAPPINGS = {
+    "TCFG": TCFG,
+}
+
+NODE_DISPLAY_NAME_MAPPINGS = {
+    "TCFG": "Tangential Damping CFG",
+}

nodes.py

@@ -2283,6 +2283,7 @@ def init_builtin_extra_nodes():
         "nodes_string.py",
         "nodes_camera_trajectory.py",
         "nodes_edit_model.py",
+        "nodes_tcfg.py"
     ]
 
     import_failed = []