Ibn al-Haytham's Pinhole Camera (Qamara)

In the 11th century, Ibn al-Haytham used a darkened chamber with a small opening — the qamara — to prove experimentally that light travels in straight lines and that vision works by light entering the eye, overturning a thousand years of extramission theory. This simulator rebuilds that experiment in 3D: a lit object stands before a wall pierced by an adjustable pinhole, and every ray that survives the aperture is traced onto a screen behind it, forming a real, inverted, rescaled image exactly as similar-triangle geometry predicts. Sliders move the object and screen and resize the aperture; live readouts track magnification, image height and the geometric blur diameter, and a ray-bundle mode reveals the penumbra cones that show why a smaller hole sharpens the image at the cost of brightness.