diff --git a/examples/webgl-sea-level.html b/examples/webgl-sea-level.html index 71dcc94131..f05ee6c812 100644 --- a/examples/webgl-sea-level.html +++ b/examples/webgl-sea-level.html @@ -11,7 +11,7 @@ docs: > values ranging from 0 to 1. The band operator is used to select normalized values from a single band.

- After converting the normalized RGB values to elevation, the interpolate expression + After converting the normalized RGB values to elevation, the case expression is used to pick colors to apply at a given elevation. Instead of using constant numeric values as the stops in the colors array, the var operator allows you to use a value that can be modified by your application. When the user drags the diff --git a/examples/webgl-sea-level.js b/examples/webgl-sea-level.js index b985d17322..4b34d003d0 100644 --- a/examples/webgl-sea-level.js +++ b/examples/webgl-sea-level.js @@ -9,7 +9,24 @@ const attributions = '© MapTiler ' + '© OpenStreetMap contributors'; -const elevation = new TileLayer({ +// band math operates on normalized values from 0-1 +// so we scale by 255 to align with the elevation formula +// from https://cloud.maptiler.com/tiles/terrain-rgb/ +const elevation = [ + '+', + -10000, + [ + '*', + 0.1 * 255, + [ + '+', + ['*', 256 * 256, ['band', 1]], + ['+', ['*', 256, ['band', 2]], ['band', 3]], + ], + ], +]; + +const layer = new TileLayer({ opacity: 0.6, source: new XYZ({ url: @@ -23,28 +40,10 @@ const elevation = new TileLayer({ level: 0, }, color: [ - 'interpolate', - ['linear'], - // band math operates on normalized values from 0-1 - // so we scale by 255 to align with the elevation formula - // from https://cloud.maptiler.com/tiles/terrain-rgb/ - [ - '+', - -10000, - [ - '*', - 0.1 * 255, - [ - '+', - ['*', 256 * 256, ['band', 1]], - ['+', ['*', 256, ['band', 2]], ['band', 3]], - ], - ], - ], - // use the `level` style variable as a stop in the color ramp - ['var', 'level'], + 'case', + // use the `level` style variable to determine the color + ['<=', elevation, ['var', 'level']], [139, 212, 255, 1], - ['+', 0.01, ['var', 'level']], [139, 212, 255, 0], ], }, @@ -61,7 +60,7 @@ const map = new Map({ tileSize: 512, }), }), - elevation, + layer, ], view: new View({ center: fromLonLat([-122.3267, 37.8377]), @@ -73,7 +72,7 @@ const control = document.getElementById('level'); const output = document.getElementById('output'); const listener = function () { output.innerText = control.value; - elevation.updateStyleVariables({level: parseFloat(control.value)}); + layer.updateStyleVariables({level: parseFloat(control.value)}); }; control.addEventListener('input', listener); control.addEventListener('change', listener);