text: // Copyright (c) 2019 Uber Technologies, Inc.
  //
  // Permission is hereby granted, free of charge, to any person obtaining a copy
  // of this software and associated documentation files (the "Software"), to deal
  // in the Software without restriction, including without limitation the rights
  // to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  // copies of the Software, and to permit persons to whom the Software is
  // furnished to do so, subject to the following conditions:
  //
  // The above copyright notice and this permission notice shall be included in
  // all copies or substantial portions of the Software.
  //
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  // AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  // LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  // THE SOFTWARE.
  
  export default `
  #define SHADER_NAME imagery-layer-vertex-shader
  
  attribute vec2 texCoords;
  
  uniform bool hasHeightMap;
  uniform sampler2D heightMapTexture;
  uniform vec4 heightMapBounds;
  uniform vec2 heightRange;
  uniform vec4 imageryBounds;
  
  varying vec2 vTexCoord;
  
  // HACK/ib - Expose vWorldHeight to enable derivatives in fragment shader
  varying float vWorldHeight;
  
  vec2 getUV(vec4 bounds, vec2 coords) {
    return vec2(
      (coords.x - bounds[0]) / (bounds[2] - bounds[0]),
      (coords.y - bounds[1]) / (bounds[3] - bounds[1])
    );
  }
  
  void main(void) {
    // Calculate vertex position
    vec2 position = vec2(
      mix(imageryBounds[0], imageryBounds[2], texCoords.x),
      mix(imageryBounds[1], imageryBounds[3], texCoords.y)
    );
  
    float z = 0.0;
    // Handle heightMap if provided
    if (hasHeightMap) {
      vec4 heightMapColor = texture2D(heightMapTexture, getUV(heightMapBounds, position));
      float relativeHeight = heightMapColor.b;
      z = mix(heightRange[0], heightRange[1], relativeHeight);
    }
  
    vWorldHeight = z;
    vTexCoord = texCoords;
  
    gl_Position = project_position_to_clipspace(vec3(position, z), vec2(0.0), vec3(0.0));
  
    picking_setPickingColor(vec3(0., 0., 1.));
  }
  `;
  