From c177581d8f7d9d6a70a466460a5d179bf5cc83f9 Mon Sep 17 00:00:00 2001
From: maj00r <maj00r@host>
Date: Wed, 14 Oct 2026 12:25:57 +0200
Subject: [PATCH] fix(track): a point of a rail profile clamped to a cut edge
 of a lofted span is never moved past its own place nor raised past its own
 height, and the edges at a station are read from the side of the span being
 laid, so the rings at a step of an edge or at a bent mitred end no longer
 stretch points out of the profile and stand them up to 18 mm above the head
 as thin fins at the corners of wide crossings, and points of other cut rails
 sit exactly on the profile instead of up to a millimetre off it

---
 world/Segment.cpp | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/world/Segment.cpp b/world/Segment.cpp
index c5389f13..0bdcc6cc 100644
--- a/world/Segment.cpp
+++ b/world/Segment.cpp
@@ -639,8 +639,9 @@ bool TSegment::RenderLoftSpan( gfx::vertex_array &Output, glm::dvec3 const &Orig
         auto const position { glm::vec3{ point - Origin } };
         auto const parallel { glm::vec3{ across } };
         auto const offset { knots::sample( Span.offsets, Distance, 0.0 ) };
-        auto const extent { knots::sample( Span.extents, Distance, 1e6 ) };
-        auto const innerextent { knots::sample( Span.inner, Distance, -1e6 ) };
+        auto const inward { Distance + std::copysign( 1e-6, Middle - Distance ) };
+        auto const extent { knots::sample( Span.extents, inward, 1e6 ) };
+        auto const innerextent { knots::sample( Span.inner, inward, -1e6 ) };
         auto const middleextent { knots::sample( Span.extents, Middle, 1e6 ) };
         auto const middleinner { knots::sample( Span.inner, Middle, -1e6 ) };
         glm::vec3 outerwall { 0.f }, innerwall { 0.f };
@@ -710,7 +711,7 @@ bool TSegment::RenderLoftSpan( gfx::vertex_array &Output, glm::dvec3 const &Orig
                         continue;
                     }
                     auto const &other { ShapePoints[ neighbour ] };
-                    auto const t { static_cast<float>( ( limit - reach( neighbour ) ) / ( side > 0 ? std::max( outside - reach( neighbour ), 1e-6 ) : std::min( outside - reach( neighbour ), -1e-6 ) ) ) };
+                    auto const t { std::clamp( static_cast<float>( ( limit - reach( neighbour ) ) / ( side > 0 ? std::max( outside - reach( neighbour ), 1e-6 ) : std::min( outside - reach( neighbour ), -1e-6 ) ) ), 0.f, 1.f ) };
                     shape.position.y = glm::mix( other.position.y, shape.position.y, t );
                     shape.texture.x = glm::mix( other.texture.x, shape.texture.x, t );
                     auto const blend { glm::mix( other.normal, shape.normal, t ) };
@@ -744,7 +745,7 @@ bool TSegment::RenderLoftSpan( gfx::vertex_array &Output, glm::dvec3 const &Orig
                         shape.position.y = std::max( shape.position.y, bottom );
                     }
                 }
-                outside = limit;
+                outside = ( side > 0 ? std::min( outside, limit ) : std::max( outside, limit ) );
                 auto const onwall { paired ? ( false == open( partner ) && clamped( partner ) == side ) : moved == count };
                 if( onwall ) {
                     wall = ( side > 0 ? outerwall : innerwall );