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Code Issues 151 Wiki Activity

refactor(track): the cap of a lofted rail end takes its texture from cap_texture and its triangles from ear_clip instead of computing both inside cap_loft

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maj00r
2026-10-14 09:57:04 +02:00
parent 3d1c97442c
commit 08d439a2f6
1 changed files with 85 additions and 67 deletions
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152
world/RailLayer.cpp
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@@ -14,7 +14,90 @@ http://mozilla.org/MPL/2.0/.
namespace track_rails {
namespace {
// in the colour of the top of the rail foot
glm::vec2 cap_texture( std::vector<gfx::basic_vertex> const &Ring, std::vector<glm::dvec2> const &Plan ) {
auto bottom { 0.0 }, top { 0.0 };
for( auto const &point : Plan ) {
bottom = std::min( bottom, point.y );
top = std::max( top, point.y );
}
auto web { Ring[ 0 ].texture };
auto nearest { std::numeric_limits<double>::max() };
for( std::size_t j = 0; j < Ring.size() / 2; ++j ) {
auto const distance { std::abs( Plan[ j ].y - 0.5 * ( bottom + top ) ) };
if( distance < nearest ) {
nearest = distance;
web = Ring[ j ].texture;
}
}
auto lowest { std::numeric_limits<double>::max() };
for( std::size_t j = 0; j < Ring.size() / 2; ++j ) {
if( Ring[ j ].normal.y > 0.5f && Plan[ j ].y < lowest ) {
lowest = Plan[ j ].y;
web = Ring[ j ].texture;
}
}
return web;
}
std::vector<std::array<std::size_t, 3>> ear_clip( std::vector<glm::dvec2> const &Polygon ) {
auto const cross = []( glm::dvec2 const &A, glm::dvec2 const &B, glm::dvec2 const &C ) {
return ( B.x - A.x ) * ( C.y - A.y ) - ( B.y - A.y ) * ( C.x - A.x ); };
double area { 0.0 };
for( std::size_t j = 0; j < Polygon.size(); ++j ) {
auto const &a { Polygon[ j ] };
auto const &b { Polygon[ ( j + 1 ) % Polygon.size() ] };
area += a.x * b.y - b.x * a.y;
}
auto const orientation { area < 0.0 ? -1.0 : 1.0 };
std::vector<std::size_t> left( Polygon.size() );
for( std::size_t j = 0; j < Polygon.size(); ++j ) {
left[ j ] = j;
}
std::vector<std::array<std::size_t, 3>> triangles;
while( left.size() > 3 ) {
auto ear { left.size() };
for( std::size_t j = 0; j < left.size() && ear == left.size(); ++j ) {
auto const &a { Polygon[ left[ ( j + left.size() - 1 ) % left.size() ] ] };
auto const &b { Polygon[ left[ j ] ] };
auto const &c { Polygon[ left[ ( j + 1 ) % left.size() ] ] };
auto const turn { cross( a, b, c ) * orientation };
if( turn < -1e-12 ) {
continue;
}
auto inside { false };
if( turn > 1e-12 ) {
for( auto const k : left ) {
auto const &p { Polygon[ k ] };
if( p == a || p == b || p == c ) {
continue;
}
if( cross( a, b, p ) * orientation > 1e-12 && cross( b, c, p ) * orientation > 1e-12 && cross( c, a, p ) * orientation > 1e-12 ) {
inside = true;
break;
}
}
}
if( false == inside ) {
ear = j;
}
}
if( ear == left.size() ) {
ear = 0;
}
triangles.push_back( { left[ ( ear + left.size() - 1 ) % left.size() ], left[ ear ], left[ ( ear + 1 ) % left.size() ] } );
left.erase( left.begin() + ear );
}
triangles.push_back( { left[ 0 ], left[ 1 ], left[ 2 ] } );
return triangles;
}
} // namespace
void cap_loft( gfx::vertex_array const &Strip, std::size_t const Ring, bool const Start, bool const End, gfx::vertex_array &Triangles ) {
if( Ring < 3 || Strip.size() < 2 * Ring ) {
@@ -48,77 +131,12 @@ void cap_loft( gfx::vertex_array const &Strip, std::size_t const Ring, bool cons
}
across = glm::normalize( across );
std::vector<glm::dvec2> plan;
auto bottom { 0.0 }, top { 0.0 };
for( auto const &vertex : ring ) {
auto const offset { vertex.position - ring[ 0 ].position };
plan.emplace_back( glm::dot( offset, across ), offset.y );
bottom = std::min<double>( bottom, offset.y );
top = std::max<double>( top, offset.y );
}
auto web { ring[ 0 ].texture };
auto nearest { std::numeric_limits<double>::max() };
for( std::size_t j = 0; j < Ring / 2; ++j ) {
auto const distance { std::abs( plan[ j ].y - 0.5 * ( bottom + top ) ) };
if( distance < nearest ) {
nearest = distance;
web = ring[ j ].texture;
}
}
auto lowest { std::numeric_limits<double>::max() };
for( std::size_t j = 0; j < Ring / 2; ++j ) {
if( ring[ j ].normal.y > 0.5f && plan[ j ].y < lowest ) {
lowest = plan[ j ].y;
web = ring[ j ].texture;
}
}
auto const cross = []( glm::dvec2 const &A, glm::dvec2 const &B, glm::dvec2 const &C ) {
return ( B.x - A.x ) * ( C.y - A.y ) - ( B.y - A.y ) * ( C.x - A.x ); };
double area { 0.0 };
for( std::size_t j = 0; j < plan.size(); ++j ) {
auto const &a { plan[ j ] };
auto const &b { plan[ ( j + 1 ) % plan.size() ] };
area += a.x * b.y - b.x * a.y;
}
auto const orientation { area < 0.0 ? -1.0 : 1.0 };
std::vector<std::size_t> left( Ring );
for( std::size_t j = 0; j < Ring; ++j ) {
left[ j ] = j;
}
std::vector<std::array<std::size_t, 3>> triangles;
while( left.size() > 3 ) {
auto ear { left.size() };
for( std::size_t j = 0; j < left.size() && ear == left.size(); ++j ) {
auto const &a { plan[ left[ ( j + left.size() - 1 ) % left.size() ] ] };
auto const &b { plan[ left[ j ] ] };
auto const &c { plan[ left[ ( j + 1 ) % left.size() ] ] };
auto const turn { cross( a, b, c ) * orientation };
if( turn < -1e-12 ) {
continue;
}
auto inside { false };
if( turn > 1e-12 ) {
for( auto const k : left ) {
auto const &p { plan[ k ] };
if( p == a || p == b || p == c ) {
continue;
}
if( cross( a, b, p ) * orientation > 1e-12 && cross( b, c, p ) * orientation > 1e-12 && cross( c, a, p ) * orientation > 1e-12 ) {
inside = true;
break;
}
}
}
if( false == inside ) {
ear = j;
}
}
if( ear == left.size() ) {
ear = 0;
}
triangles.push_back( { left[ ( ear + left.size() - 1 ) % left.size() ], left[ ear ], left[ ( ear + 1 ) % left.size() ] } );
left.erase( left.begin() + ear );
}
triangles.push_back( { left[ 0 ], left[ 1 ], left[ 2 ] } );
auto const web { cap_texture( ring, plan ) };
auto const triangles { ear_clip( plan ) };
for( auto const &triangle : triangles ) {
for( auto const &order : { std::array<int, 3>{ 0, 1, 2 }, std::array<int, 3>{ 0, 2, 1 } } ) {
for( auto const k : order ) {