<aside> ℹ️ Project: Toy Trains Date: 03/2022 Context: The design of the most fundamental system in the game - placing objects on a grid.

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Basics

• Grid is three-dimensional. Developer can set the size of each axis.
• Grid Point knows, if its occupied or not.

Snapping

• Set of points on the grid are chosen for the object based on Snap Position Calculation
• When snapped, object is always rotated to the position where its local vector up equals world vector up. Its top always faces the sky.
• On Y axis, only four angles are valid - 0, 90, 180, 270.
• When the player release the pinch button, object is placed on the grid.

Preview

• When the object's distance to the grid is equal or lower than the snap distance, preview is activated.

• Preview is activated and placed on the calculated snap position.

• When preview is active, model grabbed in the hand disappears. Put it another way - at the same time, only one of the objects (either object in the hand or object's preview) can be active.

• Preview has a transparent gray material.

• When the player release the pinch button in the snapping mode, object is placed on the grid and preview disappears.

  

Snap Position Calculation

• Snap Range is calculated between Grid Point Center and Object Center (the same as the one for grabbing, not the pivot).
• Every item covers x number of Grid Points on the grid. They can be organized in different shapes (not only straight, but for example 'L' shaped).
• One of the object's Grid Point is considered a reference main point.