Segments are the price: five balls
The same radius five times. The fourth ball uses the defaults.
three.js ships ready-made shapes: box, sphere, cylinder, torus, plane, capsule and tube. Each is a grid of vertices joined into triangles, and the segment numbers you pass decide how round it looks and how many triangles it costs.
Change the code and press Run (Ctrl+Enter). Predict what will happen first, then break it on purpose and read what changes. Your edits are saved and match the lesson page.
Ready for more? This phase has 4 hands-on exercises with automatic checks.
Practice questions
Write the code in the editor, run it, then open the model answer to compare.
Build a CylinderGeometry for a bike tube with radius 0.02 and length 0.5, with 8 sides. Print its triangle count, then predict what 16 sides gives and check.
You need a bell for the bike: a dome. Which built-in shape would you start from, and how would you cut it in half?
Explain it without notes
Why does the default sphere have 960 triangles but only 561 vertices?
A shape is missing from your scene and there is no error. Name three geometry-side things you would check.
Console
Nothing logged yet.Expected console output
6 x 4 -> 36 triangles (formula 36)
12 x 8 -> 168 triangles (formula 168)
20 x 12 -> 440 triangles (formula 440)
32 x 16 -> 960 triangles (formula 960)
64 x 32 -> 3968 triangles (formula 3968)
drawn: 5 draw calls, 5572 triangles
geometries on the GPU: 5