aboutsummaryrefslogtreecommitdiff
path: root/src/shader/code/collide.glsl
blob: 3f4e2c555dfabd637c2562a7400ad8985e6d3000 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
static const std::string COLLIDE_SHADER_CODE = R"(
#version 430

layout (local_size_x = 1, local_size_y = 1) in;

layout (std430, binding=1) buffer bufferCollide  { float collideCells[];  };
layout (std430, binding=2) buffer bufferStream   { float streamCells[];   };
layout (std430, binding=3) buffer bufferFluid    { float fluidCells[];    };

/// external influence

uniform int  mouseState;
uniform vec2 mousePos;

/// LBM constants

uniform uint nX;
uniform uint nY;

const uint  q         = 9;
const float weight[q] = float[](
	1./36., 1./9., 1./36.,
	1./9. , 4./9., 1./9. ,
	1./36 , 1./9., 1./36.
);

const float tau   = 0.8;
const float omega = 1/tau;

/// Vector utilities

float comp(int i, int j, vec2 v) {
	return i*v.x + j*v.y;
}

float sq(float x) {
	return x*x;
}

float norm(vec2 v) {
	return sqrt(sq(v.x)+sq(v.y));
}

/// Array indexing

uint indexOfDirection(int i, int j) {
	return 3*(i+1) + (j+1);
}

uint indexOfLatticeCell(uint x, uint y) {
	return q*nX*y + q*x;
}

uint indexOfFluidVertex(uint x, uint y) {
	return 3*nX*y + 3*x;
}

/// Data access

float w(int i, int j) {
	return weight[indexOfDirection(i,j)];
}

float get(uint x, uint y, int i, int j) {
	return collideCells[indexOfLatticeCell(x,y) + indexOfDirection(i,j)];
}

void set(uint x, uint y, int i, int j, float v) {
	collideCells[indexOfLatticeCell(x,y) + indexOfDirection(i,j)] = v;
}

void setFluid(uint x, uint y, vec2 v) {
	const uint idx = indexOfFluidVertex(x, y);
	fluidCells[idx + 0] = v.x;
	fluidCells[idx + 1] = v.y;
}

int getMaterial(uint x, uint y) {
	const uint idx = indexOfFluidVertex(x, y);
	return int(fluidCells[idx + 2]);
}

void setMaterial(uint x, uint y, int m) {
	const uint idx = indexOfFluidVertex(x, y);
	fluidCells[idx + 2] = m;
}

/// Moments

float density(uint x, uint y) {
	const uint idx = indexOfLatticeCell(x, y);
	float d = 0.;
	for ( int i = 0; i < q; ++i ) {
		d += collideCells[idx + i];
	}
	return d;
}

vec2 velocity(uint x, uint y, float d) {
	return 1./d * vec2(
		get(x,y, 1, 0) - get(x,y,-1, 0) + get(x,y, 1, 1) - get(x,y,-1,-1) + get(x,y, 1,-1) - get(x,y,-1,1),
		get(x,y, 0, 1) - get(x,y, 0,-1) + get(x,y, 1, 1) - get(x,y,-1,-1) - get(x,y, 1,-1) + get(x,y,-1,1)
	);
}

/// Equilibrium distribution

float equilibrium(float d, vec2 v, int i, int j) {
	return w(i,j) * d * (1 + 3*comp(i,j,v) + 4.5*sq(comp(i,j,v)) - 1.5*sq(norm(v)));
}

/// Disable wall interior

void disableWallInterior(uint x, uint y) {
	int wallNeighbors = 0;

	for ( int i = -1; i <= 1; ++i ) {
		for ( int j = -1; j <= 1; ++j ) {
			const int material = getMaterial(x+i,y+j);
			if ( material  == 0 || material == 2 || material == 3 ) {
				++wallNeighbors;
			}
		}
	}

	if ( wallNeighbors == 9 ) {
		setMaterial(x,y,0);
	}
}

/// Determine external influence

float getExternalPressureInflux(uint x, uint y) {
	if ( mouseState == 1 && norm(vec2(x,y) - mousePos) < 2 ) {
		return 1.5;
	} else {
		return 0.0;
	}
}

bool isWallRequestedAt(uint x, uint y) {
	if ( mouseState == 2 && norm(vec2(x,y) - mousePos) < 2 ) {
		return true;
	} else {
		return false;
	}
}

/// Actual collide kernel

void main() {
	const uint x = gl_GlobalInvocationID.x;
	const uint y = gl_GlobalInvocationID.y;

	if ( !(x < nX && y < nY) ) {
		return;
	}

	const int material = getMaterial(x,y);

	if ( isWallRequestedAt(x,y) && material == 1 ) {
		setMaterial(x,y,3);
		return;
	}

	if ( material == 3 ) { // manually added wall
		disableWallInterior(x,y);
	}

	if ( material == 1 ) { // fluid
		const float d = max(getExternalPressureInflux(x,y), density(x,y));
		const vec2  v = velocity(x,y,d);

		setFluid(x,y,v);

		for ( int i = -1; i <= 1; ++i ) {
			for ( int j = -1; j <= 1; ++j ) {
				set(x,y,i,j, get(x,y,i,j) + omega * (equilibrium(d,v,i,j) - get(x,y,i,j)));
			}
		}
	}
}
)";