Briefing Document: Understanding Raycasts in Unity

Introduction

This document provides a comprehensive overview of raycasting in Unity, drawing from two key sources: "Raycasts in Unity (made easy)" and "Raycasts, Explained. Every Physics 'Cast' Visualized | Unity Tutorial". These sources provide complementary perspectives, covering the fundamentals, different types of casts, and performance considerations. This document aims to consolidate this information for a clear understanding of the subject.

Key Themes and Concepts

1. What are Raycasts?

• Definition: At its core, a raycast is a process of projecting a line (a ray) from a point in a specific direction to detect collisions with objects in the game world. Think of it as a thin, invisible line being shot out into your game.
• As described in "Raycasts, Explained...", "...a ray you can think about it as a very very tiny thin line that goes from one point in a direction."
• Use Cases: Raycasts are highly versatile, enabling a wide array of functionalities. Common applications include:
• Object selection by clicking or pointing.
• Weapon firing.
• Enemy line-of-sight detection.
• Ground checks and distance measurements.
• Cliff detection.
• Jumping checks.
• Basically anytime you need to understand the world around you.
• "Raycasts in Unity..." highlights "you can use a raycast to select another object by clicking on it or pointing at it you can use them to shoot weapons or create an enemy's line of sight or you could use a raycast to detect what's around an object such as to perform a ground check or measure how high up an object is..."
• "Raycasts, Explained..." states "basically anytime we need to understand the world around us we're generally using raycast in unity"

1. The Anatomy of a Raycast

• Ray: A Ray data structure containing:
• Origin: A Vector3 point in world space where the ray starts.
• Direction: A normalized Vector3 defining the ray's travel direction. Normalised Vectors have a length of one and therefore define direction only.
• The sources emphasize you can define the ray from the mouse position, the center of the viewport, or manually by providing an origin and direction.
• "Raycasts in Unity..." notes "the origin is a vector3 position in the world that the ray will start from such as the transform position of an object for example while the direction of travel is defined by a normalized vector 3."
• RaycastHit: A data structure that stores information about a collision when a raycast hits an object:
• The object that was hit.
• The collision point.
• The collider tag.
• Both sources point out that you might declare this inside or outside of your function.
• "Raycasts in Unity..." states "when array does successfully hit something you'll be able to use the raycast hit data to check what the object was where it happened or the tag of the collider that was hit"
• Raycast Function: The method used to perform the raycast operation: