From e4c7163e9d6a2065b601cb048f3c64e193c2f387 Mon Sep 17 00:00:00 2001
From: Zhongyue GUAN <79921457+AliceZhongyueGUAN@users.noreply.github.com>
Date: Fri, 8 Dec 2023 19:33:36 +0800
Subject: [PATCH 1/4] Formula change

---
 docs/Basics/Stamp/stampRound.frag | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/Basics/Stamp/stampRound.frag b/docs/Basics/Stamp/stampRound.frag
index d798168..bf0b683 100644
--- a/docs/Basics/Stamp/stampRound.frag
+++ b/docs/Basics/Stamp/stampRound.frag
@@ -33,7 +33,7 @@ void main() {
     // The quadratic equation
     float a, b, c, delta;
     a = 1.0 - pow(cosTheta, 2.0);
-    b = - 2.0 * (r0 * cosTheta + pLocal.x);
+    b = 2.0 * (r0 * cosTheta - pLocal.x);
     c = pow(pLocal.x, 2.0) + pow(pLocal.y, 2.0) - pow(r0, 2.0);
     delta = pow(b, 2.0) - 4.0*a*c;
     if(delta <= 0.0) discard;

From e25724b09b0af46de41b358a068c50fe83c33f39 Mon Sep 17 00:00:00 2001
From: Zhongyue GUAN <79921457+AliceZhongyueGUAN@users.noreply.github.com>
Date: Sat, 9 Dec 2023 16:37:40 +0800
Subject: [PATCH 2/4] Color issue solved

---
 docs/Basics/Stamp/stampRound.frag | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/Basics/Stamp/stampRound.frag b/docs/Basics/Stamp/stampRound.frag
index bf0b683..8e5301e 100644
--- a/docs/Basics/Stamp/stampRound.frag
+++ b/docs/Basics/Stamp/stampRound.frag
@@ -56,7 +56,7 @@ void main() {
 
     // The main loop to sample and blend color from the footprint.
     int MAX_i = 128; float currIndex = startIndex;
-    vec4 currColor = vec4(0.0);
+    vec4 currColor = vec4(0.0,0.0,0.0,1e-10);
     for(int i = 0; i < MAX_i; i++){
         float currStampLocalX = interval * (currIndex - index0);
         float currStampRadius = r0 - cosTheta * currStampLocalX;

From d278e051870e9060284f81ab3bae9683a161a976 Mon Sep 17 00:00:00 2001
From: Zhongyue GUAN <79921457+AliceZhongyueGUAN@users.noreply.github.com>
Date: Sat, 9 Dec 2023 16:40:04 +0800
Subject: [PATCH 3/4] Color issue solved with comment

---
 docs/Basics/Stamp/stampSquare.frag | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/docs/Basics/Stamp/stampSquare.frag b/docs/Basics/Stamp/stampSquare.frag
index c45369d..ff94e19 100644
--- a/docs/Basics/Stamp/stampSquare.frag
+++ b/docs/Basics/Stamp/stampSquare.frag
@@ -46,7 +46,7 @@ void main() {
     if(startIndex > endIndex) discard;
 
     int MAX_i = 128; float currIndex = startIndex;
-    vec4 currColor = vec4(0.0);
+    vec4 currColor = vec4(0.0,0.0,0.0,1e-10); // set alpha as 1e-10 to avoid numerical error
     for(int i = 0; i < MAX_i; i++){
         float currStampLocalX = interval * (currIndex - index0);
         vec2 pToCurrStamp = pLocal - vec2(currStampLocalX, 0.0);
@@ -63,4 +63,4 @@ void main() {
     }
     outColor = currColor;
     return;
-}
\ No newline at end of file
+}

From 585c53be887a9fb73498ab7da897054e0c506f18 Mon Sep 17 00:00:00 2001
From: Zhongyue GUAN <79921457+AliceZhongyueGUAN@users.noreply.github.com>
Date: Sat, 9 Dec 2023 16:40:43 +0800
Subject: [PATCH 4/4] color issue solved with comment

---
 docs/Basics/Stamp/stampRound.frag | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/Basics/Stamp/stampRound.frag b/docs/Basics/Stamp/stampRound.frag
index 8e5301e..42e8d8f 100644
--- a/docs/Basics/Stamp/stampRound.frag
+++ b/docs/Basics/Stamp/stampRound.frag
@@ -56,7 +56,7 @@ void main() {
 
     // The main loop to sample and blend color from the footprint.
     int MAX_i = 128; float currIndex = startIndex;
-    vec4 currColor = vec4(0.0,0.0,0.0,1e-10);
+    vec4 currColor = vec4(0.0,0.0,0.0,1e-10);    // set alpha as 1e-10 to avoid numerical error
     for(int i = 0; i < MAX_i; i++){
         float currStampLocalX = interval * (currIndex - index0);
         float currStampRadius = r0 - cosTheta * currStampLocalX;