The workflow is separated into four steps:
1. Model Loader (Flux)
This is where you can change the Flux model, add LoRAs (optional) and type your prompt
2. ControlNet
This is where you load your lineart file (drag the file onto the Load Image node). You need to play around with the Canny parameters (low_threshold, high_threshold) until you have an image that has the contours you want, without too many extra lines that will make it harder for Flux to come up with a matching result. Hit Queue, then Cancel Current Run once the canny image appears in Preview Image. Once you are happy with the canny image, you can set the Apply ControlNet parameters: strength for how strong the contours should be applied, and end_percent for when the constraints can be released (ie. 50% means that after the first half of the generation, the model can do what it wants). If these parameters are too strict, Flux won't find a good solution and will be putting limbs all over the place. Sometimes if the constraints are too tight, the canny lines appear in the final image, like here.
3a. Generator
When you're happy with your group 2 settings, proceed to this step. You generate an image by pressing the Queue button in ComfyUI. Flux will generate a basic image based on your chosen settings. Parameters you can set here are Steps (more steps = more detail = longer generation time). The RandomNoise node contains the seed (an integer number) that initializes the noise generator (a long story but unimportant at this point). Same seed with identical settings = same image. Different seed = different generation.
4a. Save Basic Image
This saves your generated image in the ComfyUI output folder.
4b. HighRes "Fix"
This step performs what's called the HighRes Fix step. It takes a basic image, upscales it, and re-generates it in higher resolution. This adds detail. Drawback is that it takes a lot more time. Settings you can change here are Denoise (higher is more variation) and Steps. I usually get nice results with 0.2 Denoise and 10 steps.
3b. Load Basic Image
A trick you can use is to generate a batch of basic images first without having to highres all of them. To do this, deactivate HighRes by Rightclicking on group 4b and clicking Bypass Group Nodes. Generate a bunch of basic images with HighRes deactivated. Inside the output folder, delete the basic images you don't like, keeping only the basic files you want to highres. Now deactivate the generator, group 3a. Activate HighRes by Rightclicking on group 4b and clicking Set Group Nodes to Always. Connect the Image output of group 3b: click and drag the blue dot that says Image to the image input of group 4b. Now you can use group 3b to load the basic images you want to highres (drag from your folder onto the Load Image node). Hit Queue to HighRes your selected image.
