From 556f6cea377f6e8620d05081946f8b469b8a1339 Mon Sep 17 00:00:00 2001
From: Adrian Kummerlaender
Date: Mon, 17 Dec 2018 21:01:53 +0100
Subject: Clean up stream and collide compute shaders
---
src/shader/code/collide.glsl | 91 ++++++++++++++++++++++++++------------------
src/shader/code/stream.glsl | 7 ++++
2 files changed, 60 insertions(+), 38 deletions(-)
(limited to 'src')
diff --git a/src/shader/code/collide.glsl b/src/shader/code/collide.glsl
index f960dcd..cef2549 100644
--- a/src/shader/code/collide.glsl
+++ b/src/shader/code/collide.glsl
@@ -7,13 +7,24 @@ layout (std430, binding=1) buffer bufferCollide{ float collideCells[]; };
layout (std430, binding=2) buffer bufferStream{ float streamCells[]; };
layout (std430, binding=3) buffer bufferFluid{ float fluidCells[]; };
+const float displayAmplifier = 10.;
+
+/// LBM constants
+
uniform uint nX;
uniform uint nY;
-const uint q = 9;
-const float omega = 0.6;
+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 displayAmplifier = 10.;
+const float tau = 0.8;
+const float omega = 1/tau;
+
+/// Vector utilities
float comp(int x, int y, vec2 v) {
return x*v.x + y*v.y;
@@ -27,30 +38,54 @@ float norm(vec2 v) {
return sqrt(sq(v.x)+sq(v.y));
}
+/// Array indexing
+
+uint indexOfDirection(int i, int j) {
+ return 3*(j+1) + (i+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[q*nX*y + q*x + (i+1)*3 + j+1];
+ return collideCells[indexOfLatticeCell(x,y) + indexOfDirection(i,j)];
}
void set(uint x, uint y, int i, int j, float v) {
- collideCells[q*nX*y + q*x + (i+1)*3 + j+1] = v;
+ collideCells[indexOfLatticeCell(x,y) + indexOfDirection(i,j)] = v;
}
void setFluid(uint x, uint y, vec2 v, float d) {
- fluidCells[3*nX*y + 3*x + 0] = float(x)-nX/2;// + displayAmplifier*v.x;
- fluidCells[3*nX*y + 3*x + 1] = float(y)-nY/2;// + displayAmplifier*v.y;
- fluidCells[3*nX*y + 3*x + 2] = displayAmplifier * norm(v);
+ const uint idx = indexOfFluidVertex(x, y);
+ fluidCells[idx + 0] = float(x) - nX/2;
+ fluidCells[idx + 1] = float(y) - nY/2;
+ fluidCells[idx + 2] = displayAmplifier * norm(v);
}
+/// Moments
+
float density(uint x, uint y) {
- return collideCells[q*nX*y + q*x + 0]
- + collideCells[q*nX*y + q*x + 1]
- + collideCells[q*nX*y + q*x + 2]
- + collideCells[q*nX*y + q*x + 3]
- + collideCells[q*nX*y + q*x + 4]
- + collideCells[q*nX*y + q*x + 5]
- + collideCells[q*nX*y + q*x + 6]
- + collideCells[q*nX*y + q*x + 7]
- + collideCells[q*nX*y + q*x + 8];
+ const uint idx = indexOfLatticeCell(x, y);
+ return collideCells[idx + 0]
+ + collideCells[idx + 1]
+ + collideCells[idx + 2]
+ + collideCells[idx + 3]
+ + collideCells[idx + 4]
+ + collideCells[idx + 5]
+ + collideCells[idx + 6]
+ + collideCells[idx + 7]
+ + collideCells[idx + 8];
}
vec2 velocity(uint x, uint y, float d) {
@@ -60,27 +95,7 @@ vec2 velocity(uint x, uint y, float d) {
);
}
-float w(int i, int j) {
- if ( i == -1 ) {
- if ( j != 0 ) {
- return 1./36.;
- } else {
- return 1./9.;
- }
- } else if ( i == 0 ) {
- if ( j != 0 ) {
- return 1./9.;
- } else {
- return 4./9.;
- }
- } else {
- if ( j != 0 ) {
- return 1./36.;
- } else {
- return 1./9.;
- }
- }
-}
+/// Actual collide kernel
void main() {
const uint x = gl_GlobalInvocationID.x;
diff --git a/src/shader/code/stream.glsl b/src/shader/code/stream.glsl
index 147b49b..982b207 100644
--- a/src/shader/code/stream.glsl
+++ b/src/shader/code/stream.glsl
@@ -6,11 +6,15 @@ 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[]; };
+/// LBM constants
+
uniform uint nX;
uniform uint nY;
const uint q = 9;
+/// Data access
+
float get(uint x, uint y, int i, int j) {
return collideCells[q*nX*y + q*x + (i+1)*3 + j+1];
}
@@ -19,6 +23,8 @@ void set(uint x, uint y, int i, int j, float v) {
streamCells[q*nX*y + q*x + (i+1)*3 + j+1] = v;
}
+/// Actual stream kernel
+
void main() {
const uint x = gl_GlobalInvocationID.x;
const uint y = gl_GlobalInvocationID.y;
@@ -30,6 +36,7 @@ void main() {
}
}
} else {
+ // rudimentary bounce back boundary handling
for ( int i = -1; i <= 1; ++i ) {
for ( int j = -1; j <= 1; ++j ) {
if ( (x > 0 || i >= 0) && x+i <= nX-1 && (y > 0 || j >= 0) && y+j <= nY-1 ) {
--
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