SampleBrushMaskRow

Sample one row of posts: post i lies at offset (Dx_mm + i × Step_mm, Dy_mm) from the brush centre.

Declaration

void SampleBrushMaskRow(const FBrushMaskDab& Dab, int64_t Dx_mm, int64_t Dy_mm, int64_t Step_mm, int32_t Count,
                                                int32_t* OutM, int32_t* OutT = nullptr);

Header: #include "Native/BrushMask.h"
Module: PublicDependencyModuleNames.Add("OrreryTerrainCore"); in your module’s Build.cs.
Stability: Experimental: supported, may change in a minor version, with a changelog line.
Thread: Pure integer arithmetic, any thread; no allocation.

Description

Writes OutM[i], the value SampleBrushMask gives at the post's local position (FBrushMaskDab::Local), or kBrushMaskOutside when the post is off the rectangle; and, when OutT is not null, OutT[i], FBrushMaskDab::SquareT_q16 there (unspecified off it).

The rotation's two accumulators step along the row by Step_mm × cos and Step_mm × sin, exact integer sums, so every value equals the per-post one bit for bit, however long the row (BrushMask.RowSampler).

Parameters

Name	Type	Default	Meaning
`Dab`	`const FBrushMaskDab&`	—	The dab, prepared by PrepareBrushMaskDab.
`Dx_mm`	`int64_t`	—	Post 0's offset from the brush centre along world X, in mm.
`Dy_mm`	`int64_t`	—	The row's offset from the brush centre along world Y, in mm.
`Step_mm`	`int64_t`	—	The spacing of the posts along world X, in mm (the cell).
`Count`	`int32_t`	—	Posts in the row, at least 0. Every post's offset, and the one a step past the last, lies within ±2^31 mm (any post of a footprint does).
`OutM`	`int32_t*`	—	Count values, out.
`OutT`	`int32_t*`	`nullptr`	Optional: Count values, out.

Note.

Pure integer arithmetic, any thread; no allocation.