From 31b740325288d9a92debc024a26bf1d689b3ac58 Mon Sep 17 00:00:00 2001
From: Guy Perfect <guytpk@gmail.com>
Date: Thu, 21 May 2026 16:23:23 -0500
Subject: [PATCH] Correction for negative affine parallax

---
 core/vip.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/core/vip.c b/core/vip.c
index 85308bf..ce94d22 100644
--- a/core/vip.c
+++ b/core/vip.c
@@ -1065,8 +1065,13 @@ static void vipDrawAffine(VB *sim, World *world) {
 
             /* Adjust left-edge parameters */
             if ((mp < 0) ^ i) {
-                mx += dx * (wx + mp);
-                my += dy * (wx + mp);
+                if (mp < 0) {
+                    mx += dx * (wx - mp);
+                    my += dy * (wx - mp);
+                } else {
+                    mx += dx * (wx + mp);
+                    my += dy * (wx + mp);
+                }
             } else {
                 mx += dx * wx;
                 my += dy * wx;