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Last active March 15, 2017 22:04
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// Copyright 2014 Michael A. R. Duncan
// You are free to do whatever you want with this source
//
// File: Galaxy1Compute.compute
// Each #kernel tells which function to compile; you can have many kernels
#pragma kernel UpdateStars
#include "Galaxy.cginc"
// blackmagic
#define BLOCKSIZE 128
RWStructuredBuffer<Star> stars;
Texture2D HueTexture;
// refer to http://forum.unity3d.com/threads/163591-Compute-Shader-SamplerState-confusion
SamplerState samplerHueTexture;
// time ellapsed since last frame
float deltaTime;
const float Softening=3e4f;
#define Softening2 Softening * Softening
static float G = 6.67300e-11f;
static float DefaultMass = 1000000.0f;
// Do a pre-calculation assuming all the stars have the same mass
static float GMM = G*DefaultMass*DefaultMass;
[numthreads(BLOCKSIZE,1,1)]
void UpdateStars (uint3 id : SV_DispatchThreadID)
{
uint i = id.x;
uint numStars, stride;
stars.GetDimensions(numStars, stride);
float3 position = stars[i].position;
float3 velocity = stars[i].velocity;
float3 A=float3(0,0,0);
[loop]
for (uint j = 0; j < numStars; j++)
{
if (i != j)
{
float3 D = stars[j].position - stars[i].position;
float r = length(D);
float f = GMM / (r * r + Softening2);
A += f * normalize(D);
}
}
velocity += A * deltaTime;
position += velocity * deltaTime;
if (i < numStars)
{
stars[i].velocity = velocity;
stars[i].position = position;
stars[i].accelMagnitude = length(A);
}
}
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