Height Calc

The procedural terrain the game generates rather than stores.

Most tiles carry their own height, but the ones that do not fall back to layered value noise that depends only on the tile’s world position - so it can be reproduced exactly here. See THeightCalc.Calculate for one tile and THeightCalc.CalculateArea for a region.

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HeightCalc.Setup

procedure THeightCalc.Setup();

Fills the blend weights the noise interpolation reads. Called once at startup by cache.simba.

A noise layer sampled every frequency tiles blends between its samples along a cosine curve, and a tile can only sit at one of frequency positions within a sample. CoarseWeights holds the four weights of the layer sampled every 4 tiles and MidWeights the two of the layer sampled every 2, so THeightCalc.CalculateArea indexes them rather than going back to the cosine table per row and column.

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HeightCalc.Noise

function THeightCalc.Noise(x, y: Integer): Integer;

A repeatable pseudo-random value from 0 to 255 for a point.

It is a hash rather than a random number: the same point always gives the same value, which is what lets the client generate terrain on the fly instead of storing it, and lets this reproduce the terrain the client would have generated.

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HeightCalc.Interpolate

function THeightCalc.Interpolate(a, b, x, frequency: Integer): Integer;

Blends from a to b along a cosine curve, x steps of the way through frequency.

A cosine rather than a straight line, so that the terrain flattens out as it approaches each grid point instead of meeting the next slope at a crease.

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HeightCalc.SmoothedNoiseArea

function THeightCalc.SmoothedNoiseArea(x, y, width, height: Integer): TIntegerMatrix;

THeightCalc.Noise smoothed over the 3x3 block around each point of a width by height rectangle whose top-left corner is x, y, returned indexed [x, y].

Neighbouring points overlap by two thirds, so laying the raw noise out once and reading it back nine times costs a ninth of the Noise calls that smoothing each point on its own would.

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HeightCalc.InterpolatedNoiseArea

function THeightCalc.InterpolatedNoiseArea(x, y, size, frequency: Integer; constref weights: array of Integer): TIntegerMatrix;

One noise layer for every tile of a size by size square whose corner is x, y: smoothed noise sampled every frequency tiles, with the tiles in between blended from the four samples around them. weights are that layer’s blend weights, from THeightCalc.Setup.

The whole square shares a handful of samples, so they are built as a grid first rather than re-derived for every tile.

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HeightCalc.CalculateArea

function THeightCalc.CalculateArea(x, y, size: Integer): TIntegerMatrix;

The procedural height of every tile of a size by size square whose corner is x, y, returned indexed [x, y], from 10 to 60. x and y are world tile coordinates already moved by the client’s 932731, 556238 offset.

The height is three noise layers summed: one sampled every 4 tiles, one every 2 tiles at half the weight, and one every tile at a quarter of the weight.