# Select openCL devices for Vray RT GPU

**URL:** <https://forums.chaos.com/t/select-opencl-devices-for-vray-rt-gpu/51034>\
**Category:** General\
**Created:** [September 15, 2014, 9:19pm UTC](https://forums.chaos.com/t/select-opencl-devices-for-vray-rt-gpu/51034 "2014-09-15T21:19:55Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![3dvizual](https://avatars.discourse-cdn.com/v4/letter/3/a9a28c/32.png) [@3dvizual](https://forums.chaos.com/u/3dvizual)\
**Post date:** [September 15, 2014, 9:19pm UTC](https://forums.chaos.com/t/select-opencl-devices-for-vray-rt-gpu/51034/1 "2014-09-15T21:19:55Z")

</div>

Is it only possible to get the effect og assigning number of GPU’s after restarting 3ds max.?

I have 3 gpu’s in my computer and I turn some of these on and off from time to time. But I only see the effect of these selections after restart of 3ds max. Is that correct or a bug.?

---

<div class="post-metadata">

**Author:** ![savage309](https://dub1.discourse-cdn.com/chaosprd/user_avatar/forums.chaos.com/savage309/32/40144_2.png) [@savage309](https://forums.chaos.com/u/savage309)\
**Post date:** [September 15, 2014, 9:44pm UTC](https://forums.chaos.com/t/select-opencl-devices-for-vray-rt-gpu/51034/2 "2014-09-15T21:44:08Z")

</div>

> [@Smoke dark and thin in VRay but awesome in GPU and Scanline](https://forums.chaos.com/t/smoke-dark-and-thin-in-vray-but-awesome-in-gpu-and-scanline/45765/3):
>
> Is it only possible to get the effect og assigning number of GPU’s after restarting 3ds max.?
> 
> I have 3 gpu’s in my computer and I turn some of these on and off from time to time. But I only see the effect of these selections after restart of 3ds max. Is that correct or a bug.?

The tool is just settings environment variable, so it is normal that you have to restart the app in order the changes to have any effect (when you use OpenCL device select to choose your devices, in the log you can find the very same message, that notifies you about the need of restarting the app).

---

<div class="post-metadata">

**Author:** ![vlado](https://avatars.discourse-cdn.com/v4/letter/v/779978/32.png) [@vlado](https://forums.chaos.com/u/vlado)\
**Post date:** [September 16, 2014, 8:04am UTC](https://forums.chaos.com/t/select-opencl-devices-for-vray-rt-gpu/51034/3 "2014-09-16T08:04:37Z")

</div>

It may be possible to add a bit of code to the V-Ray RT render server to detect changes to the system environment and attempt to re-read the new info… will make a note to look into it.

Best regards,  
Vlado

---

<div class="post-metadata">

**Author:** ![3dvizual](https://avatars.discourse-cdn.com/v4/letter/3/a9a28c/32.png) [@3dvizual](https://forums.chaos.com/u/3dvizual)\
**Post date:** [September 18, 2014, 6:54am UTC](https://forums.chaos.com/t/select-opencl-devices-for-vray-rt-gpu/51034/4 "2014-09-18T06:54:36Z")

</div>

Great Vlado.