A Hydra chain rendered to o1..o3 stays invisible unless that buffer is selected with render()

Hydra has multiple output buffers o0..o3, but only one is shown on the canvas at a time. The default visible output is o0, so a chain ending in .out(o1) renders correctly but never appears on screen. To view a non-default buffer, either end the main chain in .out(o0), or call render(o1) to switch the visible buffer. Mixing up .out(oN) (which buffer a chain writes to) with render(oN) (which buffer is shown) leaves the canvas blank or showing the wrong image.

Examples

osc(10).out(o1) — renders but invisible. Fix: .out(o0), or add render(o1) to view it.

Assessment

Explain why a Hydra chain ending in .out(o1) can show nothing on the canvas, and give the two ways to make it visible.