remark. ray-casting/ray-tracing/ray-marching [ag-001E]

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The ray-casting/ray-tracing/ray-marching algorithms simply apply one of the multitude of root finding methods to solve the ray intersection equation.

In general, ray-tracing typically uses a bunch of geometry (e.g. closed-form formulas) to calculate the intersection point, while ray-marching marches along the ray, and uses numerical methods to find the intersection point.

The term ray-casting was introduced concurrently with ray-tracing in the 1980s, nowadays it could be used to mean the general ray intersection process, or specifically the ray-marching process with fixed step size.