function hillshade(demData) {
let azimuthrad = this.constants.azimuth * 0.017453292519943295;
let altituderad = this.constants.angleAltitude * 0.017453292519943295;
let gradX, gradY;
let yPos = this.constants.ySize - this.thread.y;
if(this.thread.x==0) gradX = demData[yPos][this.thread.x+1] - demData[yPos][this.thread.x];
else if(this.thread.x==this.constants.xSize-1) gradX = demData[yPos][this.thread.x] - demData[this.thread.y][this.thread.x-1];
else gradX = (demData[yPos][this.thread.x+1] - demData[yPos][this.thread.x])/2 + (demData[yPos][this.thread.x] - demData[yPos][this.thread.x-1])/2;
if(yPos==0) gradY = demData[yPos+1][this.thread.x] - demData[yPos][this.thread.x];
else if(yPos==this.constants.ySize-1) gradY = demData[yPos][this.thread.x] - demData[yPos-1][this.thread.x];
else gradY = (demData[yPos+1][this.thread.x] - demData[yPos][this.thread.x])/2 + (demData[yPos][this.thread.x] - demData[yPos-1][this.thread.x])/2;
let slope = 3.141593/2 - Math.atan(Math.sqrt(gradX*gradX + gradY*gradY));
let aspect = Math.atan(-gradY, gradX); //should be atan2, but not working!
let hs_value = Math.sin(altituderad) * Math.sin(slope)
+ Math.cos(altituderad) * Math.cos(slope)
* Math.cos(azimuthrad - aspect);
this.color(hs_value, hs_value, hs_value);
}
Purpose-built for displays of data
Observable is your go-to platform for exploring data and creating expressive data visualizations. Use reactive JavaScript notebooks for prototyping and a collaborative canvas for visual data exploration and dashboard creation.
