ID 357278 - Input lag when using certain view styles if an environment image enabled.

Problem summary
If you have an Environment Image enabled and set the 3D Viewport View Type to:

Directional Light with any projection type set for the environment image or;
Camera with the environment image projection type set to Front Projection

There is lag when dropping out of a navigation / interaction action. The larger the image file, the more lag is induced. 

Below is a comparison gif of Direction Light vs Perspective when a 2560 x 1440 targa file is being used for the environment image:​

Customer reported version
modo.12.1v1

Customer reported platform
10.13

Steps to reproduce

1) In Modo 12.1v1, create a default primitive. 

2) In the Shader Tree tab, open the environment material, then load an image file for use via Add Layer > (load image). The larger resolution the image, the more severe the lag.

3) In the top left corner of the 3D Viewport, change from a Perspective view to a Direction Light view. Alternatively, change from Perspective to a Camera view and change the Projection Type to Front Projection for the environment image. Be sure to set the active camera as the Projection Camera for the environment image.

4) Interact with the 3D Viewport by making quick navigation inputs - Modo will lag registering the actions. 

Workaround
Disable the environment image when using a Directional Light view style for the 3D Viewport.

Reproduced by support
This bug has been reproduced in:
Windows 10
12.1v1

macOS 10.13
12.1v1

Unable to reproduce bug in:
Windows 10
12.0v1

macOS 10.13.
12.0v1

Earliest version tested
Modo 12.0v1 - This issue no longer appears in this version and has regressed.

Expected behaviour
No performance drop when an environment image is enabled and you interact with the 3D Viewport using a Directional Light view style. 

Actual behaviour
Modo lags when an environment image is enabled and you interact with the 3D Viewport using a Directional Light view style.