Volumetric: Debug Voxel Size and Location

When displaying the voxel size for an adaptive domain the resolution of the adaptive domain was used to calculate the world size of the voxel.
This patch changes this to use the initial size of the domain.

When using adaptive domain the overlay was not rendered in the right
place.

Thanks to sebbas for part of the patch!

Reviewed By: sebbas, fclem

Differential Revision: https://developer.blender.org/D6076

Volumetric: Debug Voxel Size and Location

When displaying the voxel size for an adaptive domain the resolution of the adaptive domain was used to calculate the world size of the voxel.
This patch changes this to use the initial size of the domain.

When using adaptive domain the overlay was not rendered in the right
place.

Thanks to sebbas for part of the patch!

Reviewed By: sebbas, fclem

Differential Revision: https://developer.blender.org/D6076

Workbench: Background Dithering

Background dithering was introduced to solve banding issues on gradient backgrounds.
This patch will enable dithering based on the texture that is used for drawing.
Only when using a GPU_RGBA8 texture the dithering will be enabled.

This disables dithering for final rendering, vertex and texture paint modes.

Reviewed By: fclem

Differential Revision: https://developer.blender.org/D6056

Show Background Image Beneath Transparent Objects (Cycles only)

Camera background images were not shown under transparent objects.
This patch performs an alpha under for background images for cycles.

In order to see the difference the Film transparency needs to be turned on.

Note that workbench and EEVEE still needs to be adapted as they don't
write store alpha value in the viewport.

Side note. This implementation is already an improvement of the current behavior, what users are requesting. (Show background images underneath cycles viewport rendering.) It is clear that this patch still needs to be extended to workbench and eevee. For now that should be marked as a known limitation.

Reviewed By: fclem

Differential Revision: https://developer.blender.org/D5437

GPU: Platform Support Level

Adds a check when starting blender if your platform is supported. We use a blacklist
as drivers are updated more regular then blender (stable releases).

The mechanism detects if the support level changed or has been validated by the user previously.
Changes can happen due to users updating their drivers, but also when we change the support
level in our code base.

When the user has seen the limited support level message it is saved in the user config.
It would be better to have a system specific config section, but currently not clear
what could benefit from that.

When the platform is unsupported or has limited support a dialog box will appear including a link
to our user manual describing what to do.

**Windows**
Windows uses the MessageBox that is provided by the windows kernel.

**X11**
We use a very lowlevel messagebox for X11. It is very limited in use and can be fine tuned when needed.

**SDL/APPLE**
There is no implementation for SDL or APPLE at this moment as the platform support feature targets mostly Windows users.

Reviewed By: brecht

Differential Revision: https://developer.blender.org/D5955

CleanUp

Removed unused define in `edit_mesh_mode.c`

Clean up

Unused framebuffers in `edit_mesh_mode.c`

Code Cleanup

Removed unused shading groups in `edit_mesh_mode.c`

Fix T70187: GPU Driver: Merge Vertices Crashes ATI/Linux/OpenSource

This has been tested with 18.2.2, 19.0.8 and 19.3.0~develop.

Reviewed By: fclem

Differential Revision: https://developer.blender.org/D5886

Fix T69995: Object Drawtype Set To Solid Issues

When setting an object draw type to Solid it always used the Material
color mode. This change only sets the material color when the viewport
is set to display textures.