OcclusionSpanMap

Per horizontal band of the canvas, the merged x ranges that occluders cover across the whole band, each with the farthest depth of the occluders merged into it (conservative). An object is hidden only if one merged range covers it in every band it touches.

Constructor

new OcclusionSpanMap(
width: float,
height: float,
bandCount: integer,
): OcclusionSpanMap

Parameters

width (float) — canvas width in pixels
height (float) — canvas height in pixels
bandCount (integer) — number of horizontal bands the canvas is divided into

Instance Methods

`build(polygons: Array.<BGE.OccluderPolygon>): void`

Rebuilds the map from this frame's occluders, replacing the previous frame's spans.

Parameters

polygons (Array.<BGE.OccluderPolygon>) — convex canvas-space occluders, nearest (lowest depth) first for the tightest map

Returns

void

`getNearestDepth(): float`

The nearest depth any span claims. An object reaching this near can't be hidden.

Returns

float — a very large number when the map is empty

`isPointCovered(x: float, y: float, depth: float): boolean`

Whether a span strictly nearer than depth covers the canvas point. An object that draws over this point no nearer than depth can only be hidden if it is.

Parameters

x (float) — canvas x
y (float) — canvas y
depth (float) — the depth to compare spans against

Returns

boolean

`isHidden( minX: float, minY: float, maxX: float, maxY: float, nearestDepth: float, ): boolean`

True only if the box is covered in every band it touches by one merged span whose depth is strictly nearer than nearestDepth. A box extending off the canvas is never hidden. The caller inflates the box by any safety margin first.

Parameters

minX (float) — left edge of the box
minY (float) — top edge of the box
maxX (float) — right edge of the box
maxY (float) — bottom edge of the box
nearestDepth (float) — depth of the nearest point of the object

Returns

boolean — true if the object is certainly hidden

`getBandHeight(): float`

Returns

float — the height of each band in pixels

`getBandCount(): integer`

Returns

integer — the number of bands

`getBandSpans(band: integer): Array.<float>`

Parameters

band (integer) — band index, 0 at the top

Returns

Array.<float> — the band's merged spans as a flat [left, right, depth, ...] list, for debug drawing