Mercury Elevation map waterlevels /

Mercury-Elevation-map-waterlevel.pde

//based on Mercury MESSENGER Global DEM 665m v2
//https://web.archive.org/web/20210903191157/https://astrogeology.usgs.gov/search/map/Mercury/Topography/MESSENGER/Mercury_Messenger_USGS_DEM_Global_665m_v2

PImage palette, heightmap, colormap, normalmap;
PShader shader;
float progress = 0;

void setup() {
  size(2048, 1024, P3D);
  shader = loadShader("shader.glsl");
  palette = loadImage("palette.png");
  heightmap = loadImage("16k-8bit-elevation-Mercury_Messenger_DEM_Global_665m.png");
  colormap = loadImage("GlobalColor2017_equi_64ppd.1000.750.430.10percent.png");
}

void draw() {
  background(0);
    shader.set("colormap", colormap);
    shader.set("heightmap", heightmap);
    shader.set("palette", palette);
    shader.set("progress", progress);
    shader(shader);
    image(heightmap, 0, 0, width, height);
}

void mouseWheel(MouseEvent event) {
  progress += event.getCount() *.0001;
  progress = constrain(progress, 0, 1);
}

shader.glsl

uniform sampler2D colormap;
uniform sampler2D heightmap;
uniform sampler2D palette;
uniform sampler2D borders;
uniform float progress;
varying vec4 vertTexCoord;
const float fade =  0.0025;

float map(float value, float min1, float max1, float min2, float max2) {
  return min2 + (value - min1) * (max2 - min2) / (max1 - min1);
}

void main() {
  vec4 terrainColor = texture2D(colormap, vertTexCoord.st);
  vec4 heightColor = texture2D(heightmap, vertTexCoord.st);

  float elevation = (heightColor.r*256 + heightColor.g) / 256; //0..1
  vec4 waterColor = texture2D(palette, vec2(map(elevation,0,progress,0,1),0));

  float d = smoothstep(progress-fade, progress+fade, elevation);
  gl_FragColor = mix(waterColor, terrainColor, d);
}

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