Introduction: Parametric Pumpkin

Imagine going for a walk at night in your neighbourhood and in the dusk light you see a body of water illuminated in the distance. There is something sinister about an arrangement of unknown floating pumpkins, considering Chinese Water Lanterns these dark souled pumpkins appear the complete opposite.

My goal is to set up a process of manufacturing these floating pumpkins in which they are easily customised and conform to a multitude of designs: this is the process I went through to create a Floating Parametric Jack-o-Lantern.

Using the plugin Grasshopper for Rhino 3D a script was written to take a .jpeg of a cartoon face and map that face to the surface of a pumpkin through user controlled parameters. These parameters include: stalk shape and size, pumpkin segments, polygon shape that produces face outline, thickness of pumpkin (important for 3D printing) and of course the mapped .jpeg image which tells the program the shapes to cut from the pumpkin body. This process could also be reverse engineered to have a face cut from the pumpkin which is known to produce a scary shadow on a surface next to the pumpkin.

Step 1: Setting Up the Pumpkin Definition

In creating the following definition there are specific stages which need to be accomplished.

Step 2: Create Pumpkin Shape

The initial process was to create a sphere for each point on a polygon, this provides centres for the spheres equal to the amount of segments you want the pumpkin to have.

Step 3: Projection Plane

After joining these (8 in this case) spheres into a single solid brep a plane is created in preparation for remapping the .jpeg face onto, and later projecting onto the pumpkin surface.

Step 4: Face Data

On this plane the .jpeg face needs to be remapped to it. The face is remapped through a component analysing the RGB values of the image, these values are connected with points on the surface to control which ones return a greater radius for the desired polygon shape (square, hexagon, circle etc.).

Step 5: Projecting Face Onto Pumpkin Surface

After getting Grasshopper (the visual scripting plugin) to select the larger shapes their perimeter is calculated and projected onto the surface of the pumpkin.

Step 6: Splitting Pumpkin Surface

Now the curves of the .jpeg face (as interpreted by the number of polygon sides) are mapped to the surface of the pumpkin they need to now be used to cut the pumpkin surface.

Step 7: Thickening Pumpkin

Now the pumpkin surface needs to be thickened so that it is solid, and so that it can be 3D printed (later on down the track).

Step 8: Finalising Script

The last part of the script was to build the stalk and the mechanism in which the pumpkin can float and attach to it.

The power of this script allows you to change the referenced .jpeg of the face (or pattern) and this will update the model to resemble the input .jpeg.

Thank you for reading my instructable


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