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 *  * Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
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 *    contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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 */

#define STRINGIFY(A) #A

// vertex shader
const char *vertexShader = STRINGIFY(
  uniform float pointRadius;  // point size in world space
  uniform float pointScale;   // scale to calculate size in pixels
  uniform float densityScale;
  uniform float densityOffset;
  void main()
  {
    // calculate window-space point size
    vec3 posEye = vec3(gl_ModelViewMatrix * vec4(gl_Vertex.xyz, 1.0));
    float dist = length(posEye);
    gl_PointSize = pointRadius * (pointScale / dist);

    gl_TexCoord[0] = gl_MultiTexCoord0;
    gl_Position = gl_ModelViewProjectionMatrix * vec4(gl_Vertex.xyz, 1.0);

    gl_FrontColor = gl_Color;
  });

// pixel shader for rendering points as shaded spheres
const char *spherePixelShader = STRINGIFY(
  void main()
  {
    const vec3 lightDir = vec3(0.577, 0.577, 0.577);

    // calculate normal from texture coordinates
    vec3 N;
    N.xy = gl_TexCoord[0].xy*vec2(2.0, -2.0) + vec2(-1.0, 1.0);
    float mag = dot(N.xy, N.xy);

    if (mag > 1.0) discard;   // kill pixels outside circle

    N.z = sqrt(1.0-mag);

    // calculate lighting
    float diffuse = max(0.0, dot(lightDir, N));

    gl_FragColor = gl_Color * diffuse;
  });
