SLG first implementation for SD3.5 (#5404)

* SLG first implementation for SD3.5

* * Simplify and align with comfy style

comfy_extras/nodes_sd3.py

@@ -3,7 +3,7 @@ import comfy.sd
 import comfy.model_management
 import nodes
 import torch
-
+import re
 class TripleCLIPLoader:
     @classmethod
     def INPUT_TYPES(s):
@@ -95,11 +95,70 @@ class ControlNetApplySD3(nodes.ControlNetApplyAdvanced):
     CATEGORY = "conditioning/controlnet"
     DEPRECATED = True
 
+class SkipLayerGuidanceSD3:
+    '''
+    Enhance guidance towards detailed dtructure by having another set of CFG negative with skipped layers.
+    Inspired by Perturbed Attention Guidance (https://arxiv.org/abs/2403.17377)
+    Experimental implementation by Dango233@StabilityAI.
+    '''
+    @classmethod
+    def INPUT_TYPES(s):
+        return {"required": {"model": ("MODEL", ),
+                             "layers": ("STRING", {"default": "7,8,9", "multiline": False}),
+                             "scale": ("FLOAT", {"default": 3.0, "min": 0.0, "max": 10.0, "step": 0.1}),
+                             "start_percent": ("FLOAT", {"default": 0.01, "min": 0.0, "max": 1.0, "step": 0.001}),
+                             "end_percent": ("FLOAT", {"default": 0.15, "min": 0.0, "max": 1.0, "step": 0.001})
+                                }}
+    RETURN_TYPES = ("MODEL",)
+    FUNCTION = "skip_guidance"
+
+    CATEGORY = "advanced/guidance"
+
+
+    def skip_guidance(self, model, layers, scale, start_percent, end_percent):
+        if layers == "" or layers == None:
+            return (model, )
+        # check if layer is comma separated integers
+        assert layers.replace(",", "").isdigit(), "Layers must be comma separated integers"
+        def skip(args, extra_args):
+            return args
+
+        model_sampling = model.get_model_object("model_sampling")
+
+        def post_cfg_function(args):
+            model = args["model"]
+            cond_pred = args["cond_denoised"]
+            cond = args["cond"]
+            cfg_result = args["denoised"]
+            sigma = args["sigma"]
+            x = args["input"]
+            model_options = args["model_options"].copy()
+        
+            for layer in layers:
+                model_options = comfy.model_patcher.set_model_options_patch_replace(model_options, skip, "dit", "double_block", layer)
+            model_sampling.percent_to_sigma(start_percent)
+            sigma_start = model_sampling.percent_to_sigma(start_percent)
+            sigma_end = model_sampling.percent_to_sigma(end_percent)
+            sigma_ = sigma[0].item()
+            if scale > 0 and sigma_ > sigma_end and sigma_ < sigma_start:
+                (slg,) = comfy.samplers.calc_cond_batch(model, [cond], x, sigma, model_options)
+                cfg_result = cfg_result + (cond_pred - slg) * scale
+            return cfg_result
+
+        layers = re.findall(r'\d+', layers)
+        layers = [int(i) for i in layers]
+        m = model.clone()
+        m.set_model_sampler_post_cfg_function(post_cfg_function)
+
+        return (m, )
+
+
 NODE_CLASS_MAPPINGS = {
     "TripleCLIPLoader": TripleCLIPLoader,
     "EmptySD3LatentImage": EmptySD3LatentImage,
     "CLIPTextEncodeSD3": CLIPTextEncodeSD3,
     "ControlNetApplySD3": ControlNetApplySD3,
+    "SkipLayerGuidanceSD3": SkipLayerGuidanceSD3,
 }
 
 NODE_DISPLAY_NAME_MAPPINGS = {