s&box SnapGrid: World-space snap grid overlay

SnapGrid: World-Space Snap Grid Overlay

SnapGrid is a sealed class that manages a world-space snap grid overlay projected onto a surface plane. It is used by the weld tool to provide visual feedback for snapping positions to a grid on surfaces.

Type Signature

public sealed class SnapGrid
{
    public float CellSize { get; set; }
    public float MaskRadius { get; set; }
    public float GridSize { get; set; }
    public Vector3 LastSnapWorldPos { get; private set; }

    public SnapGrid(float cellSize = 4f, float maskRadius = 64f, float gridSize = 48f);
    public void Update(SceneWorld world, GameObject hoveredObject, Vector3 aimWorldPos, Vector3 hitNormalWorld);
    public void Hide();
    public void Destroy();
    
    public static (int cx, int cy, Vector3 snapPos, float snapU, float snapV, bool snapAxisX, bool snapAxisY) ComputeSnap(
        Vector3 faceOriginWs, Vector3 faceRightWs, Vector3 faceUpWs, float cellSize, Vector3 aimPosWs);
}

Properties

• float CellSize - The size of each grid cell in world units.
• float MaskRadius - The radius around the aim point where the grid is visible.
• float GridSize - Fallback half-extent used when the hovered object has no usable bounds.
• Vector3 LastSnapWorldPos - The snapped world-space position of the highlighted corner.

Methods

Constructor

Update(SceneWorld world, GameObject hoveredObject, Vector3 aimWorldPos, Vector3 hitNormalWorld)

• Creates or updates the scene object for rendering
• Recalculates the plane when the surface normal or hovered object changes
• Aligns the grid with the object's natural rotation
• Scales down cell size to fit within the object's face
• Computes the nearest snap line and updates the shader attributes

Hide()

Destroy()

ComputeSnap(...)

• cx, cy: Grid corner indices
• snapPos: Snapped world position
• snapU, snapV: UV coordinates on the grid
• snapAxisX, snapAxisY: Whether snapping to X or Y axis

Behavior

• The grid aligns with the object's natural rotation on every face, including tilted surfaces
• Cell size automatically scales down to fit within the object's face
• Near corners snap to the intersection and show both lines
• Uses model-local bounds when available for tight, rotation-aware OBB calculation
• Falls back to world AABB from colliders when model bounds are unavailable
• Supports holding use to lock the plane while moving

Usage

// Create a snap grid for the weld tool
var snapGrid = new SnapGrid(cellSize: 4f, maskRadius: 64f, gridSize: 48f);

// Update every frame while hovering an object
snapGrid.Update(Scene.SceneWorld, hoveredObject, aimWorldPos, hitNormalWorld);

// Get the snapped position
var snappedPos = snapGrid.LastSnapWorldPos;

// Hide when not hovering
snapGrid.Hide();

// Clean up when done
snapGrid.Destroy();

Notes

• Uses a custom shader (shaders/snap_grid.shader) for rendering
• Implements SceneDynamicObject for overlay rendering with depth
• Has a cheat convar snapgridno_fade to disable fade masking
• The grid projects the object's up vector onto the face plane for natural orientation