This ray tracing example does a great job at demonstrating the key concept behind the fisheye lens: instead of producing images with straight lines of perspective, fisheye lenses use a special mapping which gives images a characteristic convex non-rectilinear appearance. The distortion and curvature of the rays show thee source of the non-rectilinear appearance!
See here for more:
https://en.wikipedia.org/wiki/Fisheye_lens
This ray tracing example does a great job at demonstrating the key concept behind the fisheye lens: instead of producing images with straight lines of perspective, fisheye lenses use a special mapping which gives images a characteristic convex non-rectilinear appearance. The distortion and curvature of the rays show thee source of the non-rectilinear appearance!
See here for more: https://en.wikipedia.org/wiki/Fisheye_lens