2e:null 2f:["$","title",null,{"children":"Hillshading the Grand Canyon | Jeremy Ashkenas | Observable"}] 34:[] 32:{"id":"6a212968df3aad72","slug":"hillshading-the-grand-canyon","title":"Hillshading the Grand Canyon","thumbnail":"d18b1cc26e4c6346149f5aaf88a100c365d5fb6733c7033daeaec5486bfa9e99","access_level":"public","create_time":"$D2019-03-11T17:50:20.892Z","update_time":"$D2019-03-11T20:24:33.122Z","view_time":null,"first_public_time":"$D2019-03-11T18:46:18.777Z","has_unpublished_edits":null,"fork":false,"stars":5,"starred":false,"owner":{"type":"team","id":"172cc08ef8a18a4b","login":"jashkenas","name":"Jeremy Ashkenas","avatar_url":"https://avatars-next.observableusercontent.com/fa1903f8171d4621ef49de28e0ff1fb965960ec87df175d8b543c4b09508b45b","tier":"starter_2024"},"version":118,"publish_version":118,"role":null,"authored":false,"authors":[{"type":"individual","id":"783616ba9fb55f5d","login":"jashkenas","name":"Jeremy Ashkenas","avatar_url":"https://avatars-next.observableusercontent.com/fa1903f8171d4621ef49de28e0ff1fb965960ec87df175d8b543c4b09508b45b","tier":null}],"members":[{"type":"individual","id":"783616ba9fb55f5d","login":"jashkenas","name":"Jeremy Ashkenas","avatar_url":"https://avatars-next.observableusercontent.com/fa1903f8171d4621ef49de28e0ff1fb965960ec87df175d8b543c4b09508b45b","tier":null,"role":"editor"}],"comments":[],"custom_thumbnail":false,"trashed":false,"lapsed":null,"subscribed":null,"forks":2,"collection":null,"type":"notebook","body":{"title":"Hillshading the Grand Canyon","cells":[{"id":0,"value":"md`# Hillshading the Grand Canyon\n\n\n*Refs: [@sahilchinoy’s](https://observablehq.com/@sahilchinoy) [Hillshader](https://observablehq.com/@sahilchinoy/hillshader), [A faster hillshader](https://observablehq.com/@sahilchinoy/a-faster-hillshader), and [Multidirectional hillshader](https://observablehq.com/@sahilchinoy/multidirectional-hillshader)\n*`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":71,"value":"html`\n\n

${drawMap(colorData)}

${drawMap(\n hillshadeMultidirectional(demData)\n )}

\n`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":9,"value":"grandCanyonDEM =\n \"https://gist.githubusercontent.com/jashkenas/3832929d51c806c0bd142fac5175b2ae/raw/3192d6c475577e62f687dc5df96272c2ee2fbae4/gc_dem_cropped.png\"","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":91,"value":"colorScale = d3\n .scaleLinear()\n .domain([0, 20, 100, 150, 200, 275])\n .range([\"#3a81c1\", \"#96c0e6\", \"#42ab74\", \"#84ecd0\", \"#cef7b9\", \"#fff\"])","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":17,"value":"height = 719","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":46,"value":"hillshadeMultidirectional = demData => {\n var imageData = new Uint8ClampedArray(demData.length);\n\n const aspectData = getAspectData(demData);\n\n const azimuths = [225, 270, 315, 360];\n\n const weights = azimuths.map(d => generateWeightMatrix(aspectData, d));\n\n const maps = azimuths.map(d => hillshader(demData, d, 45));\n\n for (var n = 0; n < demData.length; n += 4) {\n const val = parseInt(\n azimuths\n .map((d, i) => weights[i][n] * maps[i][n])\n .reduce((a, b) => a + b) / 2\n );\n\n imageData[n] = val;\n imageData[n + 1] = val;\n imageData[n + 2] = val;\n imageData[n + 3] = 255;\n }\n\n return imageData;\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":51,"value":"import {getAspectData, generateWeightMatrix} with {demData, height} from \"@sahilchinoy/multidirectional-hillshader\"","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":48,"value":"import {hillshader, drawHillshade} with {height, demData} from '@sahilchinoy/a-faster-hillshader'","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":11,"value":"import {d3, drawMap, demData, drawHillshade, colorData} with {grandCanyonDEM as molokai, height, colorScale} from \"@sahilchinoy/hillshader\"","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"}],"files":"$W34","stdlib":"1","titling":"auto"}} 33:"$32:body"