2 files changed, 13 insertions, 3 deletions
diff --git a/src/shader/code/collide.glsl b/src/shader/code/collide.glsl
index 3510c4e..23e98f9 100644
--- a/src/shader/code/collide.glsl
+++ b/src/shader/code/collide.glsl
@@ -44,7 +44,7 @@ float norm(vec2 v) {
 /// Array indexing
 
 uint indexOfDirection(int i, int j) {
-	return 3*(j+1) + (i+1);
+	return 3*(i+1) + (j+1);
 }
 
 uint indexOfLatticeCell(uint x, uint y) {
diff --git a/src/shader/code/stream.glsl b/src/shader/code/stream.glsl
index 9b77c85..1a2abe3 100644
--- a/src/shader/code/stream.glsl
+++ b/src/shader/code/stream.glsl
@@ -13,14 +13,24 @@ uniform uint nY;
 
 const uint q = 9;
 
+// 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;
+}
+
 /// Data access
 
 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) {
-	streamCells[q*nX*y + q*x + (i+1)*3 + j+1] = v;
+	streamCells[indexOfLatticeCell(x,y) + indexOfDirection(i,j)] = v;
 }
 
 /// Actual stream kernel