Put on your 3D glasses, then check the two patches below — cover one eye at a time: each eye should clearly see the patch on its own side and the other patch should look dark. If it's the other way round, press Swap eyes.
Note: ChromaDepth glasses (rainbow/prism lenses) look similar but are not two-color filters and will not work. On a laptop the tests are indicative — screen size and viewing distance aren't calibrated — and a headset (a used Quest 2 works) remains the recommended instrument. Click = trigger; drag = look around.
This sends your TV a frame-packed 3D picture: one half is your left eye, the other your right eye, squeezed to fit one frame. Your TV stretches each half back out and shows it in 3D. Pick the layout your TV's 3D menu is set to:
On an LG 3D TV (passive / Cinema 3D): connect this laptop as the source, press the 3D button (or open Settings ▸ Picture ▸ 3D), choose Side by Side, and put on the polarized glasses. If you see two squished pictures, 3D mode isn't on yet; if depth looks wrong or gives you eye-strain, use 3D ▸ L/R swap on the TV (or your glasses upside-down as a quick test).
Best full-screen at the TV's native resolution. Passive sets halve one axis and the format halves the other, so this is for viewing and therapy, not fine measurement (same indicative-not-calibrated caveat as glasses mode). Press Esc to leave. Click = trigger; drag = look around.