Since we switched to the 2019 version of Solidworks, dark areas appear and disappear depending on the position. It's a disaster when we're working on a well-hollowed part.
To make it easier for you to understand my problem, I took 2 screenshots.
I would like to add that no appearance or effect has been changed or added, I am in the original Solidworks configuration.
If you don't have a scene or appearances, have you tried to play with the lights (position, intensity, activation or not, color,...)? This is because your old files may be handled differently with SW19.
You have to look in the menu View ==> Show ==> uncheck "ambient oclusion, shadow in shaded image mode==> Graphic real view + possibly cartoon -==> without forgetting to disable the loading of Photoview 360 (can be found in the add-ins downloaded at startup). Disabled photoview if you don't render all the time. Enable it only if you really use it frequently.
In the attached image, see what it does if you enable certain choices
It has nothing to do with Photoview. SW's standard lighting looks like studio lighting with ambient light and possibly spot spots, even with photoview turned off.
The problem is that this atmosphere is present even without wanting to render (which for me is stupid). If I design, I want uniform lighting regardless of the orientation of the model. If I render, I manage my lighting.
For me, you shouldn't have to deal with light when you're just designing. We should be able to see all the details, from all angles, of a room without the software putting "realistic" grey areas on us.
My modest macros are only intended to free themselves from this management of light and to allow a return to the past.