The Best Free AI Rendering Tool for Architecture

An Unsponsored Review of the Alpaca AI Rendering Engine

Art Nouveau Custom Home with Usonian Finishes

If you’re an architect or designer interested in working AI rendering tools into your design process, it can be frustrating finding the right platform to start on. There are countless options but many either have hidden paywalls, lackluster features, confusing UI’s, or just don’t offer the blend of quality and control architects are looking for. However, the goal of this blog is to share the best and most accessible AI tools and ideas for architects to explore this new field of design, which is why Pixels to Plans is excited to share this unsponsored review of Alpaca AI rendering, and show how it offers exactly what architects need in an AI platform.

Alpaca: AI Rendering Platform Review

Alpaca (a.k.a. Chroma by AlpacaML) is a free AI image generator and AI rendering tool currently in open access with some impressive capabilities for architects, especially for rendering and refining your building concepts. At the time of writing, it offers 100 free generations a day, with reasonably priced options for standard and pro plans, but for most architects looking to experiment and learn AI render tools, the free tier is plenty. You can get started experimenting with Alpaca for free at

One of the issues with many competing AI models is a lack of authorship (i.e. how much control you have over the results compared to the algorithm). A platform with poor authorship means the algorithm makes most of the decisions for you and while its results might look good, it doesn’t take direction all that well and you often can’t reliably edit the generations you get.

Alpaca fixes this issue. Its sketch-to-render and editing tools let you turn everything from well-developed Rhino models to even the worst Microsoft Paint doodles into stunning images. It also does this with a fast generation time, giving you constant feedback so you can refine the result by refining your drawing. This gives a tremendous amount of authorship to the user and makes fine tuning images a breeze compared to the uncontrollable slot machine that platforms like Midjourney provide (still love you though Midjourney).

AI architecture rendering of a green tower showing sketch to AI render capabilities of alpaca chroma
Alpaca Sketch to Render Performance
Midjourney sketch to render fail
Midjourney Struggling With the Same Sketch to Render Task

However, in the realm of architecture, it provides something even more powerful: constant massing. If you input a picture of a building or even just a massing model, Alpaca lets you generate high quality variations in finishes and style while maintaining the same general shape of the building. Imagine being able to produce a hundred high quality renders of finish options for your building in a single day, or even completely redesign the facade with the push of a button. That is the power that Alpaca gives you.

alpaca ai architecture rendering constant massing performance - facade variation example
Alpaca Constant Massing Performance

While it may not have all the advanced features of other platforms, for architecture it is a godsend because it allows you to generating high quality building images that explore different style or material alternatives for a given massing. Other models such as Stable Diffusion can yield similar or better results, but these come with a steep learning curve and don’t always maintain the massing as well on the first try. Based on my tests so far, Alpaca is the simplest and most reliable model I have found for AI rendering tasks.

As you will see in the next section, compared to how other free and paid models perform on this task, this is groundbreaking.

Key Features

Alpaca is designed as a constant composition platform with some creative fusion capabilities (see my previous post comparing image generators for an explanation of each type). Some key features of Alpaca include:

  • Image-to-Image – The image-to-image feature in Alpaca is one of the most reliable and easy to control constant composition features available, especially for a free platform. This feature allows for especially precise AI rendering.
  • Paintbrush Editing – One of Alpaca’s best strengths is its editing tools. With a few rough strokes of an MS Paint style paintbrush, you can edit your images with stunning precision since the Alpaca model is trained to understand and refine MS Paint style graphics into something spectacular.
  • Intuitive presets – The Pro, Controlled, Creative, and Wild presets make it easy for beginners to vary how much you edit an image. However, for those who want even more control, advanced slider controls are available as well.
  • Fast generations – Alpaca typically generates images in a matter of seconds.
  • Creative Fusion – Alpaca offers an excellent creative fusion tool to help you apply the style of an existing image to your current project, without the need to describe every detail of the style you want to emulate. This feature often functions much better for architecture than competitors such as Vizcom and PromeAI.

Example Projects

Of course, as with any AI image generators, why describe their capabilities when you can show them? So, let’s take a look at some benchmark prompts and example use cases of how Alpaca performs to show how architects might be able to apply this tool. We will be looking at the following examples: 

  • Façade Variations
  • Physical Model to Render
  • Updating Your Portfolio
  • Sketch to Render for Adaptive Reuse
  • Interior Remodeling

Constant Composition

In Post 3 (The Best AI Image Generators for Architecture) we explored the concept of style benchmarks for assessing how a platform interprets prompts. Let’s look at our five Pixels to Plans benchmark prompts to get an initial idea of how this model performs.

alpaca chroma - pixels to plans benchmark prompt results 1-3
alpaca chroma - pixels to plans benchmark prompt results 4-5

To compare these against the same benchmarks on other models, check out
Post 3 using the link below.

Comparison matrix for the best AI image generators using 5 prompt benchmarks. The table compares 2 styles of Midjourney, Playground AI, PromeAI, and Look.X. Read more on the link to Canva below
The Best AI Image Generators for Architecture
Confused about which AI platforms you should learn and integrate AI into your workflow? This article...

Fortunately, Alpaca interprets prompts very similarly to other platforms so if you are used to another image generator, you can often import your favorite prompts over to start integrating Alpaca into your workflow and get similar results, without having to reinvent your prompts that much. To test this out, I used ChatGPT to generate prompts in a consistent format for X styles using the prompt template below:

Prompt Template: Architecture photo of a house in a [style] style, [adjective] facade of [materials]. [Details] prominent throughout the design, with [focal points or other key features].

Then I took the following art nouveau-inspired home concept I generated previously as my base image for the experiment.

I ran this base image with each of my ChatGPT generated prompts in Alpaca to assess how well it maintains the composition while capturing a variety of styles. For comparison, I ran the same prompts using Stable Diffusion XL (SDXL) on Playground AI and achieved the results shown in the second column using a 20-30% image weight (which took several iterations to optimize).

You may notice that SDXL adds a bit more detail and texture quality to the images, it isn’t as good at maintaining consistent massing and struggles to change out all the finishes to match the prompt as well as Alpaca Alpaca. With enough prompt engineering (See Post 4), negative prompts, and varying the weight of the base image, you can achieve higher quality images with Stable Diffusion, but for the average architect just looking to quickly create some cladding variations for their existing design, Alpaca Alpaca is the superior and more user-friendly product.

However, let’s say you like the look of SDXL but the control of Alpaca? Well, why not just combine the two in a single workflow with Alpaca’s creative fusion feature? The third column shows the results of painting the style of the SDXL results onto the final image using Alpaca’s creative fusion.

You can zoom in on Canva to better understand the nuances of each output. 

Hopefully shows that for simple variations, Alpaca really shines, but for designers to really embrace AI in their workflow, they may need to understand the strengths and weaknesses of all the platforms they use, and learn how to combine them to fit their design goals.

Physical Model-to-Render

When I was in high school, I wanted to be an architect so when I got the chance to model a building in our “prototyping” class, I jumped on the chance to make a physical model of an original building inspired by my favorite architect at the time, Frank Lloyd Wright. This building was in FLW’s Usonian style (learn more about Usonian architecture at the link below) but the model was rough at best. However, with an AI like Alpaca, I was able to reimagine this model with a much more realistic visualization.

three ai generated usonian homes
Reimagining Usonian: Frank Lloyd Wright's Organic Architecture for Today’s Housing Needs
Usonian architecture offers a compelling vision for a future where homes are affordable, beautiful, and...
physical cardboard model of a usonian building next to an AI rendering of it
physical cardboard model of a usonian building next to an AI rendering of it - back yard
physical cardboard model of a usonian building next to an AI rendering of it - front door

Tools like this will be transformational for both architects and students to express their creativity in ways never before seen, with little more than some paper, glue, a camera, and a prompt.

Updating your Portfolio with AI Rendering

Let’s say you have a portfolio of well-developed designs but you’re not too happy about some of the finish choices you made. Or, maybe some of your past concepts aren’t in style anymore and you’re trying to update your existing portfolio of ideas to fit a potential client’s requests. Well, why not use an AI architecture rendering engine like Alpaca to reimagine your portfolio in a different style? 

For example, let’s say you want to take your brighter, more fantastical ideas in a darker, warmer direction with some Usonian influences. Well with a few keystrokes you can do this:

Prompt Template: Architecture photo of a house in a Usonian style, rain and fog, dark rich wood, glass, copper, overcast, Cherokee red concrete, fir trees, open breezeway, flagstone, flat roofs with overhanging eves, warm orange light in the windows, at dusk, front entrance

side by side building comparison, art nouveau to Usonian restylize - alpaca chroma AI rendering
side by side building comparison, art deco to Usonian restylize - alpaca chroma AI rendering
AI architecture rendering side by side building comparison,art deco to Usonian restylize - alpaca chroma AI rendering
AI architecture rendering side by side building comparison, Googie to Usonian restylize - alpaca chroma AI rendering

Sketch-to-Render for Adaptive Reuse

As noted above, a key feature of Alpaca is its MS Paint style tool that lets you prompt with drawings rather than words. To me, Alpaca seems to be the best free AI tool for turning illegible sketches into something beautiful compared to its competitors.

I believe this will be particularly useful for adaptive reuse, helping to visualize how obsolete or unwanted structures could be repurposed. In particular, the paint sketching feature could help architects add decorative flourishes and critical changes to the massing of existing buildings with unparalleled precision and quality. 

As an example, let’s consider a less car-centric future where parking structures might be reused as office space or housing. Sure, there would need to be some major structural and envelope changes like adding lobbies and balconies, or removing some floorplates for higher ceilings, but this tool can help architects make the fine-tuning changes needed explore what those changes might look like, helping Owners envision how they could repurpose these structures.

4 images showing an Alpaca Chroma AI Rendering Paintbrush Tool Example for Parking Garage Adaptive Reuse
Adaptive reuse of a parking structure, using Alpaca paintbrush to add a living wall, various plants, a glass elevator enclosure, and slightly larger balconies on alternating levels of the east facade.

AI Rendering for Interior Remodels

Finally, as usual, let’s not forget about the importance of interiors. Using a workflow that blends Midjourney and Alpaca, I was able to consult on a small bathroom remodel, helping the homeowners rapidly visualize how their bathroom might look with the specific tile, vanity, and mirror they were considering, taking real-time feedback and giving real-time image updates in a fraction of the time it would take to model and render such a detailed finish concept from scratch. 

marble tile
engineered marble vanity
circular backlit mirror

The Canva slideshow below shares a few snapshots from the visualization workflow. This includes a photo of the initial bathroom, initial Alpaca renders before finishes were narrowed down and priced, a Midjourney exploratory phase for visualizing randomized finish arrangements with the initial Alpaca output as an image prompt, and finally a Alpaca phase for dialing in the image by adding the toilet, mirror, structured ceramic bronze tile niche, and backsplash that Midjourney struggled to put in the right places. While Midjourney and Alpaca are not perfect, together they are great for getting a feel for how specific materials will work together in a space.


In summary, Alpaca is a simple but versatile free AI rendering and editing tool perfectly suited for architecture, which designers should consider using in their design and rendering workflow. 

If you like this type of content and want to learn more about different AI architecture tools, their use cases, and the design opportunities they could unlock, consider subscribing to the free Pixels to Plans mailing list below to be notified of new content, or read through our other posts [link].

AI Generated Art Nouveau Acanthus leaves Avatar - AI Architecture Blog

About the Author


Designer and engineer exploring the intersection of AI, architecture, and urbanism.



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