/* -*- mode: c++; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/*
 * Copyright (c) 2004-2013  HUBzero Foundation, LLC
 *
 * Authors:
 *   Wei Qiao <qiaow@purdue.edu>
 */

float4 main (float2 texCoord : TEXCOORD0,
             uniform samplerRECT posTexture : register(s0),
             uniform samplerRECT initTexture : register(s1),
             uniform sampler3D vfield,
             uniform float3 scale,
             uniform float maxScale,
             uniform float useInitPos,
             uniform float timeStep,
             uniform float currentTime) : COLOR
{
    if (maxScale > 100) maxScale = 100;

    float3 oldPosition = f3texRECT(posTexture, texCoord);
    float3 velocity = tex3D(vfield, oldPosition).yzw - float3(0.5, 0.5, 0.5);
    velocity = velocity * (2 * maxScale);
    velocity = velocity * scale;
	
    float3 position = oldPosition + velocity * timeStep * 0.01;
    //float3 position = oldPosition;

    //if (useInitPos) {
        if ((position.x < 0) || (position.x > 1) || 
            (position.y < 0) || (position.y > 1) || 
            (position.z < 0) || (position.z > 1)) {
            position = f3texRECT(initTexture, texCoord);
        }
    //}

    return float4(position, 1);
}

float4 initParticlePosMain(float3 initPos : TEXCOORD0,
                           float2 texCoord : TEXCOORD1,
                           float timeStep : TEXCOORD2,
                           uniform sampler3D vfield) : COLOR
{
    float3 oldPosition = initPos;
    //float3 velocity = tex3D(vfield, oldPosition).yzw * 2 - float3(1, 1, 1);
    //float3 position = oldPosition + timeStep * velocity;
    //return float4(position, 1);
    return float4(initPos, 1);
}

float4 mainlines(float2 texCoord : TEXCOORD0,
                 uniform samplerRECT posTexture : register(s0),
                 uniform sampler3D vfield,
                 uniform float2 offset,
                 uniform float timeStep) : COLOR
{
    float3 oldPosition = f3texRECT(posTexture, texCoord);
    float3 velocity = tex3D(vfield, oldPosition).yzw * 2 - float3(1, 1, 1);
	
    float3 position = oldPosition + velocity * timeStep;

    return float4(position, 1);
}