Choosing an arch for the environment
I began with references for organic architecture and chose a direction with bundled ribs, columns and arches. I wanted to choose a form inside Unreal and adjust it to suit the environment I was working on.
The AI agent built the Houdini networks through MCP, which let it work in the application. I chose the direction, asked for controls and tried them in Unreal.
Four versions to work with
I like all four versions in the recent comparison. The height, number of ribs and twist give me different shapes to work with, depending on the environment. That’s what I want from the tool: being able to choose a form and adapt it inside Unreal.
The denser ribs are one of those choices. They give the arch a different structure and smaller openings. A more open arch, a taller one or tighter twists could each fit a different scene.
These four states vary the controls within the braided arch. The wider setup also included a column, an exoskeleton variant and four arch types: braided ribs, an eroded mass, branching forms and a ribbed web.
During the August tests, I could draw a curve in Unreal and have the arch follow it. The build log also records straight and curved inputs, with the feet staying on the curve.
An earlier control bug
Earlier on, I changed the rib count and got exactly the same shape. All the ribs were sitting on the same line, even though the mesh passed the closed-mesh checks. Correcting the vector attributes separated them again.
Other parts of the study
There were still details to refine in the original setup, especially the column’s profile and taper. Some of the noise added detail without doing much for the form.
Later tests included painterly materials and PCG ivy. The ivy initially missed the thin arch because the sampling area covered too much of the surrounding ground. Narrowing that area was part of the fix.
The image above is a new presentation of the mesh saved in August.
October check
An automated test reran a copy of the HDA in Houdini 21.0.440. Changing the height, rib count and braid turns produced different geometry, with no cook errors in the baseline or the three variants. The current Unreal setup has not been retested.
Related: Market Street is the larger Blender-Houdini-Unreal experiment.