# Camera Matching (Perspective Solving)

## Module Overview

This is the heart of the course, and **Anchor 2**. Given a single OSINT photo, camera matching recovers the exact camera that captured it — its position, orientation, and focal length — using the **vanishing points** of parallel lines in the image. It is the technique practitioners call the **fSpy process**. Get this right and your model is provably from the right viewpoint. Get it wrong and everything downstream inherits the error.

**Shared reference module:** read [Camera Matching](../../../techniques/1-foundation-preparation/camera-matching.md) alongside this module.

## The Video

[TODO: 2–3 sentence intro to the walkthrough — which photo is matched, and the moment to watch for.]

## How Perspective Solving Works

[TODO: the geometry in plain language. Parallel lines in 3D → vanishing points in 2D. Three mutually orthogonal vanishing points (a building corner) define the camera's orientation; with a known scale reference, the position and focal length follow. Why a simple building corner is the ideal test case.]

## The fSpy Process, Step by Step

[TODO: the practical sequence — load the photo, identify the horizon, draw lines on the three sets of parallel edges, let fSpy compute the camera, import the solution into Blender as a camera. Reference the [fSpy add-on page](../../../addons/fspy.mdx).]

## From Match to Blender

[TODO: importing the fSpy solution via the fSpy importer add-on; the reference image becomes the camera background; render resolution set to the original image dimensions; verifying the match in the viewport.]

## When a Photo Won't Solve

[TODO: scenes with few right angles (organic terrain, wide open shots); low resolution; extreme wide-angle distortion; and the fallback of combining a partial solve with known site geometry from the satellite baseline.]

## Knowledge Check

[TODO: 3 questions — e.g. what a vanishing point is; why three orthogonal vanishing points are the gold standard; what happens to the match if the horizon is misidentified.]

## Summary

[TODO: one paragraph.]

## KB References

- [Camera Matching](../../../techniques/1-foundation-preparation/camera-matching.md) — shared reference module (sidebar)
- [Camera and Perspective](../../../techniques/1-foundation-preparation/camera-and-perspective.md) — the underlying perspective concepts
- [Analyzing Footage](../../../techniques/1-foundation-preparation/analyzing-footage.md) — selecting the best frames/angles to match
- [fSpy importer](../../../addons/fspy.mdx) — bringing the solution into Blender
- [Perspective Plotter](../../../addons/perspective-plotter.mdx) — real-time in-Blender camera matching (an alternative to fSpy)