/*
 * Copyright (C) 2018 Open Source Robotics Foundation
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

#version 330

in block
{
  vec2 uv0;
  vec3 cameraDir;
} inPs;

uniform sampler2D depthTexture;

out vec4 fragColor;

uniform vec2 projectionParams;
uniform float near;
uniform float far;
uniform float min;
uniform float max;

float getDepth(vec2 uv)
{
  float fDepth = texture(depthTexture, uv).x;
  float linearDepth = projectionParams.y / (fDepth - projectionParams.x);
  return linearDepth;
}


void main()
{
  // get linear depth
  float d = getDepth(inPs.uv0);

  // reconstruct 3d viewspace pos from depth
  vec3 viewSpacePos = inPs.cameraDir * d;

  // get length of 3d point, i.e.range
  float l = length(viewSpacePos);

  if (l > far)
    l = max;
  else if (l < near)
    l = min;

  fragColor = vec4(l, 0.0, 0, 1.0);
}
