Vray sketchup GPU rendering on 2.0

[jackdicker]

Hi Guys, I got the vray sketchup 2.0 demo today to try and test out the GPU RT rendering service. It appears that none of the options are as quick as the CPU? Ive scouted the net for advice and some people are saying it needs to run a full scene to compile the information if its the first GPU render of the day. I have a pretty solid Nvidia 760 and the RT render has been going for about 15 mins and it doesn't even look finished.. IMO its no different to the CPU. Now I read online that if the GPU isnt working the RT renderer will switch back to CPU automatically... So maybe this is occurring. Can anyone give me any advice? How can I see if my GPU is actually active?

 

Thanks Guys.

 

Jack

[AJLynn]

I haven't tried this in the Sketchup version, but it looks like it has most of he same options as the Max version, so, first thing to check is whether you're actually sending the render to the GPU. In the Vray options window, in RT Engine options, there's a Mode drop-down with three options. Since you have a Geforce card, probably the one to pick is RT-GPU-CUDA. (You can let a render run for some amount of time, save the image, then switch to CPU mode and run it the same amount of time, and compare - if the GPU mode is working properly the GPU will be noticeably more developed.)

 

When you hit render you should have a bit of delay while the CUDA information is compiled and loaded. Then the window will start to show your render, which will develop over time. The speed will depend on a bunch of factors including the choice of materials and the lighting. Interior scenes usually render slower than exteriors. RT (and iray and similar engines) are very similar to Maxwell Render, except with the option to run on the GPU.

 

For anybody who was around about 8 years ago, that last sentence has a big yellow flag in "Maxwell Render." That software is slow like molasses flowing uphill. Throwing a powerful GPU at it makes it faster, like molasses on flat ground that's pouring from a large, ruptured tank. Under ideal conditions, that molasses will travel at about 35 MPH, which is really quite fast for things like molasses or the local 6 train, but not as fast as a GTI on open highway. Before I strain that analogy any more, I'll just say that in some circumstances (e.g. a high res interior that's not lit by enormous windows or a big softbox behind the camera) even a fast RT-GPU render will not reduce the noise quickly enough to be useful in production, where a skilled user of regular Vray would get the job done in less time using the regular Vray engine on the CPU, but there will be other times when the RT-GPU engine will be useful.

[Dimitris Tolios]

You can see if your GPU is active using utilities like the EVGA Precision X or MSI Afterburner that will show you clocks in real time. If the GPU is idling, it downclocks to conserve energy, if it is under load it "boosts" up. 7xx series do it depending on their temps.

 

A pretty good monitoring tool - good choice for GPU-rendering starters - is the GPU-Z by techpowerup.

Can monitor GPU load %, GPU clocks and VRam allocation (i.e. what is loaded on your GPU, which is usually more than what is actually used and in some cases more than it can actually be used at any given moment as a whole).

 

Try different drivers to see if you get better GPU utilization - newest is not always the best, the ones that came with your machine from the factory is even less likely to be the best. Same goes for those that windows downloaded themselves (if you've let them). Just go to nvidia.com for the latest drivers and get 2-3 prior versions to experiment.

 

GPU progressive rendering is "unbiased" (= it calculates every pixel in brute force mode as if you were using Quasi-Monte Carlo, but not exactly), instead of irradiance map/light cache which are "biased" techniques (i.e. those "cheat" interpolating between pixels to speed up the process).

Unbiased renderings are "doomed" to be slower than biased in most cases, but when you compare apples to apples...in RT GPU, the GPU is throwing 1000s of shaders in the fight, while your workstation might have 8, 12 or best case scenario a couple of dozens of threads.

 

Long story short, RT GPU works impressively well as an tool to setup your scene lighting and materials in most cases, and I'm eagerly wanting to try it with Sketchup. As a production engine (i.e. for final images) it lacks here and there, but depending on your horsepower (a single 760 is not bad, but...) you might struggle a bit longer than you think.

Remember, it is "20 times faster", comparing apples to apples.

Edited September 23, 2013 by dtolios