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/*********************************************************************NVMH3****
Path:  NVSDK\Common\media\programs
File:  simple.cg

Copyright NVIDIA Corporation 2002
TO THE MAXIMUM EXTENT PERMITTED BY APPLICABLE LAW, THIS SOFTWARE IS PROVIDED
*AS IS* AND NVIDIA AND ITS SUPPLIERS DISCLAIM ALL WARRANTIES, EITHER EXPRESS
OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, IMPLIED WARRANTIES OF MERCHANTABILITY
AND FITNESS FOR A PARTICULAR PURPOSE.  IN NO EVENT SHALL NVIDIA OR ITS SUPPLIERS
BE LIABLE FOR ANY SPECIAL, INCIDENTAL, INDIRECT, OR CONSEQUENTIAL DAMAGES
WHATSOEVER (INCLUDING, WITHOUT LIMITATION, DAMAGES FOR LOSS OF BUSINESS PROFITS,
BUSINESS INTERRUPTION, LOSS OF BUSINESS INFORMATION, OR ANY OTHER PECUNIARY LOSS)
ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE, EVEN IF NVIDIA HAS
BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.


Comments:

******************************************************************************/

// Simple vertex shader, derived from NVIDIA's simple.cg sample
// shader, that modulates the lit color with a noise pattern based on
// vertex position.

// define inputs from application
struct appin
{
    float4 Position     : POSITION;
    float4 Normal       : NORMAL;
};

// define outputs from vertex shader
struct vertout
{
    float4 HPosition  : POSITION;
    float4 FragPos    : TEXCOORD0;
    float4 Color0     : COLOR0;
};

vertout main(appin IN,
             uniform float4x4 ModelViewProj,
             uniform float4x4 ModelViewIT,
             uniform float4 LightVec,
             uniform float4 LightColor,
             uniform float4 DiffuseMaterial,
             uniform float4 SpecularMaterial)
{
    vertout OUT;

// Assume that the profile is PROFILE_ARBVP1...
// #ifdef PROFILE_ARBVP1
    ModelViewProj = glstate.matrix.mvp;
    ModelViewIT = glstate.matrix.invtrans.modelview[0];
    LightVec = glstate.light[0].position;
    LightColor = glstate.light[0].diffuse;
    DiffuseMaterial = glstate.material.front.diffuse;
    SpecularMaterial = glstate.material.front.specular;
// #endif

    // transform vertex position into homogenous clip-space
    OUT.HPosition = mul(ModelViewProj, IN.Position);

    // Output the post-perspective-divide position as FragPos
    float invW = 1.0f / OUT.HPosition.w;
    OUT.FragPos = OUT.HPosition * invW;

    // transform normal from model-space to view-space
    float3 normalVec = normalize(mul(ModelViewIT, IN.Normal).xyz);

    // store normalized light vector
    float3 lightVec = normalize(LightVec.xyz);

    // calculate half angle vector
    float3 eyeVec = float3(0.0, 0.0, 1.0);
    float3 halfVec = normalize(lightVec + eyeVec);

    // calculate diffuse component
    float diffuse = dot(normalVec, lightVec);

    // calculate specular component
    float specular = dot(normalVec, halfVec);

    // The lit() function is a handy function in the standard library that
    // can be used to accelerate your lighting calculations.
    //
    // This function return a vector containing these values:
    //     result.x = 1.0;
    //     result.y = max(diffuse, 0);
    //     result.z = if (result.y > 0.0) then pow(specular, 32) else 0.0
    //     result.w = 1.0;

    // Use the lit function to compute lighting vector from diffuse and
    // specular values
    float4 lighting = lit(diffuse, specular, 32);

    // combine diffuse and specular contributions
    float3 color0 = (lighting.y * DiffuseMaterial.xyz * LightColor.xyz) +
	(lighting.z * SpecularMaterial.xyz);

    // Generate a pseudo-random noise pattern
//    float3 xyz = clamp((normalVec.xyz + 1.0) * 0.5, 0.0, 1.0);
    float3 xyz = clamp((OUT.HPosition.xyz + 1.0) * 0.5, 0.0, 1.0);

    xyz = frac(xyz * 262144.0);
    float randSeed = frac(3.0 * xyz.x + 5.0 * xyz.y + 7.0 * xyz.z);

    float3 altColor;

    randSeed = frac(37.0 * randSeed);
    altColor.x = randSeed * 0.5 + 0.5;
    randSeed = frac(37.0 * randSeed);
    altColor.y = randSeed * 0.5 + 0.5;
    randSeed = frac(37.0 * randSeed);
    altColor.z = randSeed * 0.5 + 0.5;
    randSeed = frac(37.0 * randSeed);
    float altAlpha = randSeed * 0.5;

    // Apply noise and output final vertex color
    OUT.Color0.rgb = lerp(color0, altColor, altAlpha);
    OUT.Color0.a = 1.0;

    return OUT;
}