#version 120

//
// For licensing information, see http://http.developer.nvidia.com/GPUGems/gpugems_app01.html:
//
// NVIDIA Statement on the Software
//
// The source code provided is freely distributable, so long as the NVIDIA header remains unaltered and user modifications are
// detailed.
//
// No Warranty
//
// THE SOFTWARE AND ANY OTHER MATERIALS PROVIDED BY NVIDIA ON THE ENCLOSED CD-ROM ARE PROVIDED "AS IS." NVIDIA DISCLAIMS ALL
// WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF TITLE, MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
//
// Limitation of Liability
//
// NVIDIA SHALL NOT BE LIABLE TO ANY USER, DEVELOPER, DEVELOPER'S CUSTOMERS, OR ANY OTHER PERSON OR ENTITY CLAIMING THROUGH OR
// UNDER DEVELOPER FOR ANY LOSS OF PROFITS, INCOME, SAVINGS, OR ANY OTHER CONSEQUENTIAL, INCIDENTAL, SPECIAL, PUNITIVE, DIRECT
// OR INDIRECT DAMAGES (WHETHER IN AN ACTION IN CONTRACT, TORT OR BASED ON A WARRANTY), EVEN IF NVIDIA HAS BEEN ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGES. THESE LIMITATIONS SHALL APPLY NOTWITHSTANDING ANY FAILURE OF THE ESSENTIAL PURPOSE OF ANY
// LIMITED REMEDY. IN NO EVENT SHALL NVIDIA'S AGGREGATE LIABILITY TO DEVELOPER OR ANY OTHER PERSON OR ENTITY CLAIMING THROUGH
// OR UNDER DEVELOPER EXCEED THE AMOUNT OF MONEY ACTUALLY PAID BY DEVELOPER TO NVIDIA FOR THE SOFTWARE OR ANY OTHER MATERIALS.
//

//
// Atmospheric scattering vertex shader
//
// Author: Sean O'Neil
//
// Copyright (c) 2004 Sean O'Neil
//

uniform vec3 v3CameraPos;		// The camera's current position
uniform vec3 v3LightPos;		// The direction vector to the light source
uniform vec3 v3InvWavelength;	// 1 / pow(wavelength, 4) for the red, green, and blue channels
uniform float fOuterRadius;		// The outer (atmosphere) radius
uniform float fInnerRadius;		// The inner (planetary) radius
uniform float fKrESun;			// Kr * ESun
uniform float fKmESun;			// Km * ESun
uniform float fKr4PI;			// Kr * 4 * PI
uniform float fKm4PI;			// Km * 4 * PI
uniform float fScale;			// 1 / (fOuterRadius - fInnerRadius)
uniform float fScaleDepth;		// The scale depth (i.e. the altitude at which the atmosphere's average density is found)
uniform float fScaleOverScaleDepth;	// fScale / fScaleDepth


const int nSamples = 2;
const float fSamples = 2.0;

varying vec3 position;


float scale(float fCos)
{
	float x = 1.0 - fCos;
	return fScaleDepth * exp(-0.00287 + x*(0.459 + x*(3.83 + x*(-6.80 + x*5.25))));
}

void main(void)
{
	// Get the ray from the camera to the vertex, and its length (which is the far point of the ray passing through the atmosphere)
	position = gl_Vertex.xyz * fOuterRadius;
    
	gl_Position = gl_ModelViewProjectionMatrix * vec4(position, 1.0);
}