Sean L. igniuss

Realtime Fluid Simulation: Projection

The core of most real-time fluid simulators, like the one in EmberGen, are based on the "Stable Fluids" algorithm by Jos Stam, which to my knowledge was first presented at SIGGRAPH '99. This is a post about one part of this algorithm that's often underestimated: Projection

MG4_F32.mp4

Stable Fluids

The Stable Fluids algorithm solves a subset of the famous "Navier Stokes equations", which describe how fluids interact and move. In particular, it typically solves what's called the "incompressible Euler equations", where viscous forces are often ignored.

This code has been moved to a GitHub repository with the corresponding license. https://github.com/UngarMax/TelnetServer

	/*
	MIT License

	Copyright (c) [year] [fullname]

	Permission is hereby granted, free of charge, to any person obtaining a copy
	of this software and associated documentation files (the "Software"), to deal
	in the Software without restriction, including without limitation the rights
	to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	copies of the Software, and to permit persons to whom the Software is

	using UnityEngine;

	[RequireComponent( typeof(Camera) )]
	public class FlyCamera : MonoBehaviour {
	public float acceleration = 50; // how fast you accelerate
	public float accSprintMultiplier = 4; // how much faster you go when "sprinting"
	public float lookSensitivity = 1; // mouse look sensitivity
	public float dampingCoefficient = 5; // how quickly you break to a halt after you stop your input
	public bool focusOnEnable = true; // whether or not to focus and lock cursor immediately on enable

	// Quick try at doing a "print value" node for Unity ShaderGraph.
	// Tested on Unity 2019.2.17 with ShaderGraph 6.9.2.
	//
	// Use with CustomFunction node, with two inputs:
	// - Vector1 Value, the value to display,
	// - Vector2 UV, the UVs of area to display at.
	// And one output:
	// - Vector4 Color, the color.
	// Function name is DoDebug.

	Setup:
	1. Index buffer containing N quads (each 2 triangles), where N is the max amount of spheres. Repeating pattern of {0,1,2,1,3,2} + K*4.
	2. No vertex buffer.

	Render N*2 triangles, where N is the number of spheres you have.

	Vertex shader:
	1. Sphere index = N/4 (N = SV_VertexId)
	2. Quad coord: Q = float2(N%2, (N%4)/2) * 2.0 - 1.0
	3. Transform sphere center -> pos

	// NOTE DONT put in an editor folder!
	using UnityEngine;

	public class AutohookAttribute : PropertyAttribute
	{
	}