AutoCAD 2014 registry tweak turns on HW acceleration

Currently in Windows Server for use with XenApp, ACAD 2014 products (inc LT 2014) do not recognise GRID passthrough or vGPU as certified graphics devices, and so all HW accelerated features will be disabled and the app falls back to software rendering for all effects.
This can have a detrimental impact on user experience, particularly where high CCU ratios are desired.

Note that the below tweaks do NOT apply to ACAD 2015, as 2015 uses a new graphics detection API (GRID passthrough is known to be OK). I have also not tested with versions prior to 2014, so cannot comment if those use the same API here.

One method is to simply delete the xml file located at Public\Documents\AutoDesk\AutoCAD 2014\R20\PTXML\AdskHwCertificationDatabase.xml, however I found this does not always work (e.g. on a 2008R2 XenApp 6.5 host this had no effect at all).
The following is a registry tweak which forces HW acceleration features in ACAD 2014, regardless of the PTXML file.
(my summary of useful settings appear at the end).

Please note that if you device is not supported by Autodesk, you use this at your own risk. I recommend only for testing and evaluation environments rather than mission-critical XenApp deployments.

Manually Enabling Hardware Acceleration (or any feature):
Here we will be looking at the HKEY_CURRENT_USER\Software\Autodesk\AutoCAD LT\R20\ACADLT-D001:409\3DGS Configuration\FeatureData value.
The \AutoCAD\Rxx.x\ACADxx…:409\ stem will change depending on your ACAD product.

Example Structure = 7f 02 00 00 5b 02 00 00 7f 02 00 00
This binary value is split into 3 integers representing feature available, enabled, recommended.

We read the numbers in little endian, i.e. the numbers are 27F (639), 25B (603), 27F (639) in the example above.
Things become more obvious in binary form.
603 = 1001011011

From right to left, the bits are:

|Bit|Integer Value|Name                    |Comments  |
|0  |1            |Hardware Acceleration   |          |
|1  |2            |Geometry Acceleration   |          |
|2  |4            |Anti-aliasing           |          |
|3  |8            |Gooch                   |          |
|4  |16           |Shadows                 |          |
|5  |32           |Texture Compression     |          |
|6  |64           |Phong                   |          |
|7  |128          |2D Hardware Acceleration|Depracated|
|8  |256          |Disable 2D Pre-clip     |Depracated|
|9  |512          |Advanced Materials      |          |

In a nutshell, hardware acceleration is enabled if odd, or disabled if even.

Mike’s summary of useful settings:

(only the value of the middle word makes a difference, as it controls the setting in effect)
Let’s forget about the depracated features, so set these OFF.

Since modern GPUs have plenty of FB mem, disable texture compression and save some cycles needed to decompress them;
The main feature that will make a difference in performance and visual style is Antialiasing. Here are the two sets of FeatureData values to keep everything else as is, but turn AA on/off

7f 02 00 00 5b 02 00 00 7f 02 00 00 --> Antialiasing OFF; all other HW features on (except texture comp)

7f 02 00 00 5f 02 00 00 7f 02 00 00 --> Antialiasing ON; all other HW features on (except texture comp)

I found from testing that Antialiasing ON doubles the GPU compute load as viewed by nvidia-smi on a XenApp host, so if you want maximum density and can live with jaggies, turn it off!

AA on, just moving the 3d triad cursor around incurs 45% GPU util on a K2 passthrough:

AA off, just moving the 3d triad cursor around incurs 20% GPU util on a K2 passthrough:

Let me know if this helps with your GRID testing.
Any issues, please let me know!


Useful information to have – thank you for sharing!