From 15f33fd09cffe05e82f5a1008cbfc2b2b12c8187 Mon Sep 17 00:00:00 2001
From: Adrian Kummerlaender
Date: Wed, 24 Apr 2019 22:37:49 +0200
Subject: Add support for erasing walls

---
 src/main.cc                   |  8 ++++----
 src/shader/code/collide.glsl  | 12 ++---------
 src/shader/code/interact.glsl | 46 +++++++++++++++++++++++++++----------------
 3 files changed, 35 insertions(+), 31 deletions(-)

diff --git a/src/main.cc b/src/main.cc
index f3f14ec..394248c 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -213,11 +213,11 @@ int render() {
 		if ( currMouseState != 0 || prevMouseState != 0 ) {
 			auto guard = interact_shader->use();
 
-			interact_shader->setUniform("influxRequested", currMouseState == 1);
-			interact_shader->setUniform("wallRequested",   currMouseState == 2);
+			interact_shader->setUniform("wall_requested",  currMouseState == 1);
+			interact_shader->setUniform("fluid_requested", currMouseState == 2);
 
-			interact_shader->setUniform("startOfLine", prevLatticeMouseX, prevLatticeMouseY);
-			interact_shader->setUniform("endOfLine", currLatticeMouseX, currLatticeMouseY);
+			interact_shader->setUniform("start", prevLatticeMouseX, prevLatticeMouseY);
+			interact_shader->setUniform("end",   currLatticeMouseX, currLatticeMouseY);
 
 			interact_shader->dispatch(nX, nY);
 		}
diff --git a/src/shader/code/collide.glsl b/src/shader/code/collide.glsl
index e2c3212..191204e 100644
--- a/src/shader/code/collide.glsl
+++ b/src/shader/code/collide.glsl
@@ -28,7 +28,7 @@ const float invCs2 = 1./3.;
 const float physCharLength   = 1.0;
 const float physCharVelocity = 1.0;
 const float physViscosity    = 0.01;
-const float latticeCharVelocity = 0.1;
+const float latticeCharVelocity = 0.005;
 
 /// Unit conversion
 
@@ -148,14 +148,6 @@ bool isOutflowCell(int material) {
 	return material == 6;
 }
 
-float getExternalMassInflux(int material) {
-	if ( material == 4 ) {
-		return 1.5;
-	} else {
-		return 0.0;
-	}
-};
-
 float getLocalKnudsenApproximation(uint x, uint y, float d, vec2 v) {
 	float knudsen = 0.0;
 
@@ -182,7 +174,7 @@ void main() {
 
 	const int material = getMaterial(x,y);
 
-	float d = max(density(x,y), getExternalMassInflux(material));
+	float d = density(x,y);
 	vec2  v = velocity(x,y,d);
 
 	if ( isBulkFluidCell(material) ) {
diff --git a/src/shader/code/interact.glsl b/src/shader/code/interact.glsl
index cb69333..613c4cd 100644
--- a/src/shader/code/interact.glsl
+++ b/src/shader/code/interact.glsl
@@ -10,11 +10,11 @@ uniform uint nY;
 
 /// External influence
 
-uniform bool influxRequested;
-uniform bool wallRequested;
+uniform bool wall_requested;
+uniform bool fluid_requested;
 
-uniform vec2 startOfLine;
-uniform vec2 endOfLine;
+uniform vec2 start;
+uniform vec2 end;
 
 /// Vector utilities
 
@@ -39,10 +39,10 @@ float distanceToLineSegment(vec2 a, vec2 b, vec2 p) {
 }
 
 bool isNearLine(uint x, uint y, float eps) {
-	if ( startOfLine == endOfLine ) {
-		return norm(vec2(x,y) - endOfLine) < eps;
+	if ( start == end ) {
+		return norm(vec2(x,y) - end) < eps;
 	} else {
-		return distanceToLineSegment(startOfLine, endOfLine, vec2(x,y)) < eps;
+		return distanceToLineSegment(start, end, vec2(x,y)) < eps;
 	}
 }
 
@@ -83,6 +83,16 @@ void disableWallInterior(uint x, uint y) {
 	}
 }
 
+void fixWallExterior(uint x, uint y) {
+	for ( int i = -1; i <= 1; ++i ) {
+		for ( int j = -1; j <= 1; ++j ) {
+			if ( getMaterial(x+i,y+j)== 0 ) {
+				setMaterial(x+i,y+j,3);
+			}
+		}
+	}
+}
+
 /// Actual interaction kernel
 
 void main() {
@@ -97,24 +107,26 @@ void main() {
 
 	if ( material == 1 ) {
 		if ( isNearLine(x, y, 3) ) {
-			if ( influxRequested ) {
-				setMaterial(x,y,4);
-				return;
-			}
-			if ( wallRequested ) {
+			if ( wall_requested ) {
 				setMaterial(x,y,3);
 				return;
 			}
 		}
 	}
 
-	if ( material == 3 ) {
-		disableWallInterior(x,y);
+	if ( material == 0 || material == 3 ) {
+		if ( fluid_requested ) {
+			if ( isNearLine(x, y, 3) ) {
+					setMaterial(x,y,1);
+					fixWallExterior(x,y);
+					return;
+			}
+		}
 	}
 
-	if ( material == 4 ) {
-		// reset influx material after execution
-		setMaterial(x,y,1);
+
+	if ( material == 3 ) {
+		disableWallInterior(x,y);
 	}
 }
 )";
-- 
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