Hello,

Firstly I should say welcome to my first ever blog post. My aim here is to post useful things related to Poser and Daz Studio, with regards to getting the best out of your content and the software.

Today I want to talk about the Daz Studio Iray render engine, specifically how to improve render times and some detail about what you can expect from current graphics cards.

Why is the Iray render engine for Daz Studio slower?

It’s a fact that Iray is a demanding render engine, because of it’s accurate photo-realistic based core. The amount of computing power needed to accurately calculate the lighting and all the little details that go into a photo-real render, are much much greater than that of Posers Firefly and Superfly render engines. It literally takes each light source and makes millions of calculations to produce an accurate real life result. This is partly what makes Iray renders look so dam realistic and well, stunning!

But beauty comes at a price, in this case, render times. Depending on your graphics card’s, potentially painfully slow. Especially for users moving from Poser to Daz Studio for the Iray render engine.

Iray makes use of Graphic’s Cards

Because of the real life rendering feature of Iray and the way the render engine makes calculations, it performs much better using certain graphics cards, rather than your processor. Even a medium quality Graphics card has the capacity to calculate an Iray render faster than even the most expensive processor (CPU) on the market today. I am currently running a fairly modest system which includes an i7 4770 CPU and a GTX 760 (OEM) GPU. After running a few tests, I learned that the GPU is at least 3 times faster at rendering.

A render that would take 9 hours only using the CPU would take 3 Hours using only the GPU.

How to speed up Iray render speeds

So, the big question and unfortunately, potentially an expensive answer. The key to speeding up an Iray render is improving your graphics card situation. For many, this can be confusing as there are a lot of technical factors when choosing the correct graphics card for your current system. I will go over in some detail what factors you need to consider but first I will discuss the best cards available on the market for Iray.

To make things simple, I have narrowed down the 3 best cards to choose from to speed up Iray.

Firstly, Iray makes use of CUDA cores which are only present in Nvidia graphics cards, ruling out ATI straight away. I will only consider the latest Nvidia graphics cards series (currently 900) as they are more readily available for purchase than past series. It also makes sense from a cost standpoint as the old cards tend to be the same price (in terms of model like for like) but slightly less powerful. I will also rule out the Titan cards as they represent bad value for money in terms of total GPU Power. If money is not an issue, then I recommend the Titan X, as many as you can get in your PC (up to a max of 4). If money is a concern, like most of us, keep reading.

Best Current Graphics Cards for Iray

Iray rendering speeds from the graphics card are based mostly on only a few factors. The amount of CUDA cores and clock speed (and potentially the amount of VRAM the GPU Holds – Which I will come on to later). Here is a working example for you:

My current graphics card is a GTX 760 (OEM), which has 1152 CUDA cores with a clock speed of 823 MHz. I plan on upgrading to a GTX 980 TI which has 2816 CUDA Cores and a clock speed of 1000. If we take the amount of CUDA cores of each and multiply them by the clock speed, you get the following:

GTX 760 (OEM) – 1152 * 823 = 948,096
GTX 980 TI – 2816 * 1000 = 2,816,000

As you can see, the GTX 980 TI has a total power that is 3 times more powerful than the GTX 760 (OEM). That means, a scene that takes 3 hours to render, will only take 1 hour – a significant difference.

VRAM: It is also worth considering the amount of VRAM your new graphics card will hold. When you hit render, the process stores all of the scene model and texture data in the graphics card and if there is not enough, it actually performs far below it’s capacity and my result in only rendering with the CPU. For most people 4GB is enough and holds enough data for a medium sized scene plus two clothed characters comfortably. 2GB really is not enough and anything over 6GB is probably overkill. One final point, if you have one than one GPU, the VRAM does not stack, it runs and the lowest VRAM GPU in your set up. So if you have a 12GB card and a 2GB card, your VRAM is only 2GB.

You can find out the specifications of each GPU on the nvidia website here: Nvidia Deskptop GPU List.

$ to GPU Power Value and SLI

As it stands, the $ to GPU Power is the best value with the GTX 970, then the GTX 980 TI and then finally the GTX 980. You will obviously have even more GPU power if you wish to install more than one graphics card. If your PC set up will allow, having two of the same card instead of one will double your total GPU Power. This makes things interesting when it comes to the best value $ to GPU Power, as two GTX 970’s are roughly equal in power to one GTX 980 TI.

Prices fluctuate all the time, so I won’t do a list of what’s the best value set up which all the different combinations of how many graphics cards between those 3 that you can get. I will now list some fact’s that need to be taken into account before you decide what GPU(s) you plan on upgrading to.

OptiX Prime Acceleration

This is a setting that can be found in the advance tab of render settings. I strongly recommend you enable it as it speeds up renders significantly, most of the time. According to benchmarks, it only seems to be effective if you use it in combination with graphics cards alone, and not your CPU as well. You can just uncheck your CPU in the same tab. There is not a great deal of information about what it does, but faster render times is always a bonus!

Benchmarks

There is a great scene you can download as a benchmark to see how fast your system is rendering. It was created by SickleYeild, which you can download from Deviant Art. Many people have posted what speeds they are getting and which graphics cards made that possible. Don’t change any of the scene settings to get an accurate idea of what you are getting. Feel free to share your benchmarks here with a comment.

Things to consider before upgrading your GPU

  • Make sure your power-supply has enough wattage and the correct connector pins to provide enough power to your new card. Currently the GTX 980TI needs a minimum of 600w
  • If you are running more than one GPU, increase the power-supply accordingly. 2 GTX980TI’s need a minimum of 850W.
  • Make sure your motherboard has the right PCIe slots for your new card(s). 1 GTX980TI needs at least 1 Slot with 16 lanes (X16) of PCIe 2.0 or 1 Slot with 8 lanes (X8) of PCIe 3.0.
  • Make sure your CPU can cope with your new GPU. The Intel X series CPU’s are designed for 3 or more GPU’s, but the mainstream CPU’s are designed to work with a maximum of 2 GPU’s
  • Make sure your PC case has enough space for the new card, it may be bigger

In conclusion, Iray is a beast of a render engine and needs the right GPU power, set up correctly with the right PC parts, to run decent render speeds. I will wrap it up now, I hope you found the info useful!