Workflow: Converting Low-Res Sketches to High-Res Architectural Elevations with Nano Banana 2
Architectural visualization often begins with a simple, low-resolution concept sketch. These initial drawings capture the essence of a design but lack the detail required for client presentations or construction documentation. The challenge lies in enhancing these images without altering the fundamental structural intent established by the original artist. This workflow demonstrates how to use the Nano Banana 2 image-to-image capabilities to upscale and refine rough hand-drawn building lines into high-resolution architectural elevations.
The goal is not to replace the architect's vision but to augment it with realistic textures, precise linework, and professional lighting. By leveraging the specific strengths of the underlying models, users can achieve a polished final product that remains faithful to the initial concept.
Selecting the Right Model for Structural Integrity
Before initiating the conversion process, it is crucial to select the appropriate model within the Nano Banana ecosystem. Google documents Nano Banana 2 as Gemini 3.1 Flash Image (gemini-3.1-flash-image), which serves as the primary tool for this type of detailed image-to-image task. For users requiring higher fidelity in complex texture generation, Nano Banana Pro (Gemini 3 Pro Image) may offer additional depth, though it comes at a different cost structure.
It is important to note that Nano Banana 2 Lite (Gemini 3.1 Flash Lite Image) is focused on speed and cost efficiency. It is not optimized for multiple reference inputs or multi-turn sequential editing. Therefore, for a workflow that requires careful preservation of specific architectural lines and iterative refinement, Nano Banana 2 Lite should be avoided unless the user explicitly accepts its limitations regarding complex editing tasks. Do not assume features available on other pages, such as the Nano Banana Pro page, are identical to those on the Nano Banana Lite page; capabilities must be verified against the specific model documentation.
For this specific task of converting low-res sketches to high-res elevations, the standard Nano Banana 2 interface provides the necessary balance between processing power and control over the output.
Step-by-Step Conversion Workflow
Executing the conversion requires a structured approach to ensure the AI understands the relationship between the input sketch and the desired output. The following steps outline a complete start-to-finish process.
1. Input Preparation
Begin by gathering your source material. Upload a clear, albeit low-resolution, scan or photo of your hand-drawn architectural elevation. Ensure the drawing is legible, even if pixelated. The AI needs to see the existing lines to understand the structural layout. If the sketch contains handwritten notes or dimensions, include them in the upload, as they provide context for the scale and proportions of the building.
2. Crafting the Prompt
The prompt acts as the instruction manual for the AI. It must clearly state the desired outcome while emphasizing the need to preserve the original geometry. Prompt instructions describe desired outcomes; they do not guarantee identity, label, object, or typography preservation. However, a well-crafted prompt significantly increases the likelihood of success.
Example Prompt: "Refine this rough architectural sketch into a high-resolution, photorealistic building elevation. Preserve the exact structural lines, window placements, and rooflines from the input image. Add realistic textures such as brick, concrete, or glass to the facade. Apply soft, natural daylighting to create depth. Maintain the original perspective and aspect ratio. Do not change the number of floors or the position of major openings."
Note: The above text is an example prompt. Results may vary based on the specific input image and model interpretation.
3. Generating and Checking Checkpoints
Once the image and prompt are submitted, the system will generate the refined elevation. After the initial generation, perform a visual checkpoint review. Compare the output against the original sketch line-by-line. Verify that:
- The roofline matches the original slope.
- Window grids align with the drawn frames.
- No new structural elements have been hallucinated where none existed.
If the result deviates from the structural intent, you may need to adjust the prompt to be more restrictive about changes or re-upload the original sketch with a clearer emphasis on "preserving lines." Avoid making assumptions about the model's ability to perfectly replicate every pixel; instead, focus on the overall architectural accuracy.
Exporting and Using the Final Elevation
After achieving a satisfactory result through the iterative process, the final step is to export the image for use in your project. The generated high-resolution elevation can now be integrated into presentation boards, marketing materials, or further edited in standard graphic design software.
Remember that the Nano Banana tool is an AI image generation and editing utility. It is not a skincare brand, bottle, jar, or physical subject. The output is a digital asset derived from the interaction between your sketch and the AI model. While the process adds realism and detail, it does not replace the need for technical verification by a licensed architect before construction.
By following this workflow, architects and designers can efficiently bridge the gap between conceptual sketches and professional visualizations, saving time while maintaining the integrity of their original designs. The key is to treat the AI as a powerful assistant that enhances human creativity rather than a replacement for architectural judgment.
For more information on the capabilities of the models used in this workflow, refer to the official Google Gemini image generation documentation.