Pinhole Camera Model

The Pinhole Camera

Ray tracing is based on the pinhole camera model, where:

• Light passes through a single point (the pinhole/aperture)
• An image is formed on the image plane behind the pinhole
• Each point on the image corresponds to a unique ray from the scene

In Ray Tracing

In the computational model:

• The camera origin (eye point) corresponds to the pinhole aperture
• The screen plane (image plane) is where the image is formed
• Rays are traced from the eye through each pixel into the scene

Pinhole Camera Properties

• No depth of field: All distances are equally sharp (infinite depth of field)
• Perfect focus: No lens effects
• Point aperture: All rays diverge from a single point

Finite Aperture Camera

A real camera with a finite aperture (lens):

• Distributes rays over a lens disc
• Produces blur for out-of-focus objects (depth of field)
• Objects at the focus distance appear sharp

Summary

• The pinhole camera is the fundamental model for ray tracing
• The camera origin corresponds to the pinhole aperture
• All rays originate from a single point through the image plane
• Finite aperture cameras model depth of field effects

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Past Paper Questions

2025 Paper 3 Question 3(a): Explain what a pinhole camera model is and what the camera origin in ray tracing corresponds to in the pinhole model. [2 marks]