Grid-Based Building System

Name: grid-based-building-system
Rating: 76
Author: nlelouche

Overview

Calculates discrete grid coordinates from mouse position for placing objects. Ensures valid placement preventing overlaps and checking resources costs.

When to Use

•Use for City Builders (SimCity style)
•Use for Tower Defense placement
•Use for Tile-based map editors
•Use for RTS structure construction
•Use for decorating grid-based interiors

Core Concepts

Concept	Description	Formula
Snapping	Rounding float position to int	`Floor(pos / size) * size`
Occupancy	Checking if cell is free	`bool IsOccupied[x,y]`
Validation	Can build here?	`ValidPos && Resources >= Cost`
Rotation	rotating the footprint	`Swap(width, height)`

Architecture

code

┌─────────────────────────────────────────────────────────────┐
│                    BUILDING PIPELINE                        │
├─────────────────────────────────────────────────────────────┤
│                                                             │
│  INPUT SYSTEM             GHOST MANAGER (Visual)            │
│  ┌────────────────┐      ┌───────────────────────────┐      │
│  │ Mouse Raycast  │─────▶│ Move Ghost to Grid Pos    │      │
│  └────────┬───────┘      │ Set Color (Green/Red)     │      │
│           │              └───────────────────────────┘      │
│           │                                                 │
│           ▼                                                 │
│  BUILD MANAGER (Logic)    GRID DATA (Model)                 │
│  ┌────────────────┐      ┌───────────────────────────┐      │
│  │ Check Cost     │      │ Occupancy Map [,]         │      │
│  │ Validate Pos   │◀────▶│ Building References       │      │
│  │ Instantiate    │      └───────────────────────────┘      │
│  └────────────────┘                                         │
│                                                             │
└─────────────────────────────────────────────────────────────┘

Best Practices

•✅ Separate the "Ghost" (Visual) from the actual "Building" (Logic).
•✅ Use Vector3Int for all grid coordinates.
•✅ Store the Grid Data efficiently (Dictionary or 2D Array).
•✅ Implement "Refund" logic for destruction.
•❌ NEVER use Physics.Raycast for grid occupancy (too slow/unreliable); use data.
•❌ NEVER instantiate the final prefab to check if it fits.

Few-Shot Examples

Example 1: Grid Calculation

User: "Snap to 2x2 grid."

Agent:

csharp

public Vector3 GetGridPos(Vector3 worldPos, int cellSize)
{
    int x = Mathf.FloorToInt(worldPos.x / cellSize) * cellSize;
    int z = Mathf.FloorToInt(worldPos.z / cellSize) * cellSize;
    return new Vector3(x, 0, z);
}

Example 2: Validation

User: "Check if area is free."

Agent:

csharp

public bool CanBuild(Vector2Int origin, Vector2Int size)
{
    // Iterate over footprint
    for (int x = 0; x < size.x; x++)
    {
        for (int y = 0; y < size.y; y++)
        {
            if (_grid[origin.x + x, origin.y + y].IsOccupied)
                return false;
        }
    }
    return true;
}

Related Skills

•@resource-management-system - Deduct cost
•@custom-editor-scripting - Grid visualization tool