In Introduction to Roblox Studio, you learned how to create basic parts like blocks, spheres, and cylinders. These can be grouped together to create more complex models, but some objects cannot be effectively built in that way, particularly those with "hollow" regions.
To construct these types of objects in Roblox, you'll use Solid Modeling tools.
Solid modeling essentially uses two processes — Union and Negate — to creatively form complex models.
The Union tool fuses multiple parts together to form one single part.
The Negate tool removes one part's geometric shape from another part to create hollow regions.
Building an Arch
An arch is a common structural element that is easily built using solid modeling tools.
A basic arch requires three parts to assemble.
Insert a Block part and scale it up to approximately the size of a door frame.
Insert a Cylinder part and scale/rotate it to intersect the center of the block. Make sure this cylinder extends completely through the block.
Insert another Block part and place it beneath the cylinder. It should be the same width as the cylinder and its top surface should line up with the vertical center of the cylinder.
Negate Hollow Regions
To "remove" regions that should be hollow, you'll need to designate the negate parts and then union all pieces together.
- Select both the cylinder and the smaller block.
- From the Model tab, click the Negate button. This will turn the parts translucent and red.
Union All Parts
To complete the arch, finalize the colors and materials of the arch and then Union all three parts together.
- Select all three parts.
- From the Model tab, click the Union button. This will "remove" the two negated parts, leaving an open path for players to walk through the arch.
The arch is complete! As a unioned model, it becomes one single object in the workspace, versus a grouped model of multiple parts: