This is weird, the lines are not visible unless it is selected only. The 3D model works fine, but the curves are not visible.
This is my system info:
Rhino 6 SR21 2019-12-15 (Public Build, 6.21.19349.01012, Git hash:master @ a9aff0b2a2e07411210fef500868737069a15926)
License type: Evaluation, build 2019-12-15
License details: Stand-Alone
Expires on: 2020-04-05
Apple Intel 64-bit macOS Version 10.14.6 (Build 18G1012) (Physical RAM: 8Gb)
Mac Model Identifier: MacBookAir7,2
Machine name: Spoorthi’s MacBook Air
Language: en-IN (MacOS default)
Intel® HD Graphics 6000 (OpenGL ver:4.1 INTEL-12.10.14)
OpenGL Settings
Safe mode: Off
Use accelerated hardware modes: On
Redraw scene when viewports are exposed: On
Anti-alias mode: 4x
Mip Map Filtering: Linear
Anisotropic Filtering Mode: Height
Vendor Name: Intel Inc.
Render version: 4.1
Shading Language: 4.10
Maximum Texture size: 16384 x 16384
Z-Buffer depth: n/a
Maximum Viewport size: 16384 x 16384
Total Video Memory: 1536 MB
Graphics: Intel HD Graphics 6000
Displays: Color LCD (126dpi 1x)
Graphics processors
Intel HD Graphics 6000 (1536 MB)
Color LCD (1440 x 900)
USB devices
Apple Inc.: Bluetooth USB Host Controller
Logitech: USB Optical Mouse
Bluetooth devices
Cambridge Silicon Radio: Hands-Free unit, SPP Dev, Headset
Third party kernel extensions
None
Third party plugins
/usr/lib/log/liblog_network.dylib
Rhino plugins
/Applications/Rhinoceros.app/Contents/Frameworks/RhCore.framework/Resources/ManagedPlugIns/RhinoCycles.rhp “RhinoCycles” 6.21.19349.1012
/Applications/Rhinoceros.app/Contents/PlugIns/NamedSnapshots.rhp “Snapshots” 6.21.19349.1002
/Applications/Rhinoceros.app/Contents/PlugIns/PanelingTools.rhp “PanelingTools” 6.21.19349.1002
/Applications/Rhinoceros.app/Contents/Frameworks/RhCore.framework/Resources/ManagedPlugIns/Commands.rhp “Commands” 6.21.19349.1012
/Applications/Rhinoceros.app/Contents/Frameworks/RhCore.framework/Resources/ManagedPlugIns/RDK_EtoUI.rhp “RDK_EtoUI” 6.21.19349.1012
/Applications/Rhinoceros.app/Contents/PlugIns/Displacement.rhp “Displacement” 6.21.19349.1002
/Applications/Rhinoceros.app/Contents/PlugIns/RhinoRender.rhp “Rhino Render” 6.21.19349.1002
/Applications/Rhinoceros.app/Contents/Frameworks/RhMaterialEditor.framework “Renderer Development Kit” 6.21.19349.1002