Click on Surface or curve
Viewport whites out (model barely visible)
Rotate in Perspective with control /mouse
Screen comes clear
Have changed mouse, rebooted
System High Sierra 10.13.4
Model Name: iMac
Model Identifier: iMac18,3
Processor Name: Intel Core i5
Processor Speed: 3.8 GHz
Number of Processors: 1
Total Number of Cores: 4
L2 Cache (per Core): 256 KB
L3 Cache: 6 MB
Memory: 32 GB
Boot ROM Version: IM183.0157.B00
SMC Version (system): 2.41f1
Serial Number (system): C02V55B3J1GQ
Hardware UUID: CA8C93CF-05CB-56DB-95E4-60FB40915684
