Transforming Line Art into Polished 3D and 2D Images
In this workflow, we'll demonstrate how you can transform simple sketches into polished, high-quality images using a combination of ControlNet Sketch, Image to Image, and Enhance features. This method is perfect for character creation, stylized environments, and refining artwork for final use. This workflow is restricted to Flux models, as Sketch ControlNet is not supported on any other model.
We'll explore three examples to illustrate the process, keeping the explanations clear, practical, and close to real use cases.
Example 1: Simple Character Transformation
In this first example, we use a reference sketch of a young boy and his plush monster toy to create a colorful, playful final image. The goal here is to generate a vibrant 3D-style character while maintaining the original pose and structure.
For this, a detailed prompt describing the colors and textures of each element will be needed.
The model used was Cutesy 3D, ideal for producing a soft, cartoony 3D look, perfect for children's characters.
Prompt:
A cheerful young boy with light brown skin, big brown eyes, and short dark brown hair, wearing light blue pajamas with a white collar and matching cuffs. His shoes are soft blue slippers with white soles. He has his arm affectionately around a cute, fluffy monster plush toy. The plush has soft purple fur, a lighter lavender belly, and round pink cheeks. Its face is beige with large light blue eyes and a round pig-like snout in pale pink. The monster has small dark gray horns with white tips and tiny claws on its hands and feet. The background is white, letting the bright, playful colors of the characters stand out.
Steps to generate the colored image:
Select the model Cutesy 3D and click on Use this model > Generate.
Start adding a reference image with a clean line art sketch without any black filled areas.
Use ControlNet (Sketch Mode) with Influence 75 and Duration 60.
Increase the Sampling Steps to 35 to add more detail to the result.
Adjust the Influence value as needed to balance the fidelity to the reference with some creative freedom during generation. A lower influence add more creativity to your result.
After generation, you can use Enhance to further boost image quality and resolution. For more details about how Enhance works, refer to the Enhance article.
For this example, we used the following Enhance settings:
Scaling Factor: x4
Style: 3D Rendered
Preset: Balanced
Example 2: Character Refinement and Quality Improvement
In this example, we'll work with a more detailed subject: a futuristic soldier holding a weapon. The goal here is not only to colorize the sketch but also to improve the quality of the final render using Image to Image generation. This method helps fix minor deformations, enhance textures, and deliver a sharper, cleaner result.
The model used was Action Plastic, ideal for creating toy-like, detailed 3D stylized characters.
Prompt:
"A futuristic soldier in a yellow and grey suit of armor holds a large gun, standing confidently against a solid blue background."
Steps to generate the colored image:
Select the model Action Plastic and click on Use this model > Generate.
Start by adding a clean line art sketch as the reference image.
Use ControlNet (Sketch Mode) with Influence 75 and Duration 60.
Increase Sampling Steps to 35 to improve the level of detail.
After the first generation, to further refine the result:
Use Image to Image with the first colored version as reference.
Set Influence to 70 to correct minor imperfections while preserving the original structure.
Finally, use Enhance to increase the resolution and polish the final image:
Scaling Factor: x4
Style: 3D Rendered
Preset: Balanced
This approach helps maintain high fidelity to the original sketch while ensuring the final image is polished and ready for use.
As an additional example, the same workflow was applied to a "Cat Boy" character:
Example 3: Applying the Workflow to Environments
In this third example, we show how the Sketch to Render workflow can be applied to background and environment creation. We'll work through a colorful cartoon village scene as the main focus. The method remains the same as before, but applied to broader compositions and environmental details.
The model used was Cartoon Backgrounds 2.0, ideal for creating vibrant, stylized 2D environments.
Prompt:
"Colorful cartoon village street scene with thick black outlines and cel-shaded render style. Small houses with slanted roofs in shades of red-orange and terracotta, pastel-colored walls in cream, light green, and soft blue. Wooden barrels, crates, and market stands scattered along the cobblestone ground in warm brown tones. A large stone well in the center with gray shading and subtle texture. Bright cloth flags hang across the street in red, yellow, blue, and pink, adding charm and movement. Sunny day atmosphere with a soft blue sky and gentle shadows."
Steps to generate the colored image:
Select the model Cartoon Backgrounds 2.0 and click on Use this model > Generate.
Start by adding a clean line art sketch as the reference image.
Use ControlNet (Sketch Mode) with Influence 75 and Duration 60.
Set Sampling Steps to 35 to improve the line and texture clarity.
After generation, use Image to Image with the first colored version as reference:
Refine the scene using Image to Image with Influence 65.
Finalize the image with Enhance:
Scaling Factor: x4
Style: Standard
Preset: Balanced
We also applied the same workflow to a "Fantasy Forest" scene following the same process:
Key Points to Remember
ControlNet Sketch Mode requires clean line art: avoid filled black areas.
Influence Settings: Higher values stick closer to the sketch, while lower values allow more artistic freedom.
Consistency: Describe all key elements and colors clearly in the prompt.
Conclusion
The Sketch to Final Render workflow is a simple but powerful method to bring your ideas to life, whether you're creating charming characters, futuristic soldiers, or immersive environments.
With careful prompt writing, clean sketches, and strategic use of ControlNet and Image to Image, you can achieve professional results while maintaining creative flexibility.
Ready to try it with your next project? 🚀
Troubleshooting
If your image appears blurry after applying Sketch ControlNet, consider enhancing the reference image to improve overall quality. This will lead to better results in Sketch Map Detection
Was this helpful?