I am a fairly new blender user and I have recently found out that using a gpu for rendering is way faster than the cpu. In my current pc I have an Intel core i5 and an amd 7970. As you know opencl rendering isn’t yet supported by cycles which means that to take advantage of the faster render times I would need an nVidia card. To summarize, my question is: is it worth buying an nVidia card just for rendering and if so which one would you recommend.
Thanks in advance
It entirely depends on what you want to render. Currently, hair is very slow on GPU and many features are not supported, e.g. volumes and SSS. If you plan on rendering things other than that, GPU rendering is a whole different level of work and you absolutely should buy a card. It makes everything easier.
Which card you should buy also depends on how large your scenes will be. The new 750Ti is getting great reviews, and you can buy two for $300 and reach performance on par with a $1,000 Titan. But it only has 2GB of memory and big scenes with lots of polys will fill those 2GB up fast. If you think that you will keep under the 2GB limit, the 750Ti is an ideal choice that does not require a new power supply, usually even with dual cards.
If you are willing to move up the price ladder, you can future-proof yourself with the 6GB GTX 780. 6GB is a good amount of space and very few people will fill that up. If you buy an overclocked version such as the STRIX from Asus, its performance is very similar to a 780Ti, but with 6GB of memory. Sadly, Nvidia is still trying to convince people that the Titan isn’t a rip-off and is thus refusing to allow OEMs to create a 6GB variant of the 780Ti.
If I were in your shoes, and I didn’t need the memory, I would buy dual 750Ti cards. But since I’m always paranoid about buying something only to have it deprecated the next day, I would wait a couple of months to see where the prices drop and grab a 6GB 780. Then, in the future, when prices have dropped a even more and you’re desirous of increased speed, buy a second 6GB 780.
Hi, I am agree with aaronmc in most points but if you wait for new hardware you can wait often forever. 
October/November the new GTX 800 series comes with Maxwell core, then GTX 700 should get cheaper.
The first Maxwell card is the GTX 750/Ti (crazy Nvidia naming), it is as fast as my GTX 760 (Kepler core) for 2/3 cost and 50% power.
So the next GTX 860 4/8 GB will be a very interesting card but you have to wait 3 or more month for it.
Cheers, mib
From what aaronmc said I think that a 750ti is probably my best bet, since I don’t want to move up to a 780. However I don’t know of I should go for dual cards. Is the performance increase that great over a single card since I will probably be rendering simple scenes or animations?
Blender scales very well with rendering. Basically, two video cards are twice as fast as one video card. There is nothing saying that you can’t buy one and then buy another in the future when you find yourself desiring more power.
I should also specify, that this only applies to rendering. Viewport performance does not scale perfectly. I don’t know the numbers, though.
OK, final question (hopefully), is there any chance that cycles will support opencl in the near future? Because if so I think my current HD7970 would be far better than even dual 750 ti’s.
Cycles does support OpenCL, it’s just a bit dodgy right now. I’m running an old old 2.69 build that is pretty fast with my 7970 Ghz. 2.70 saw a nasty speed regression on AMD hardware.
The problem isn’t on Blender’s end, it’s on AMD’s. No one knows whether it’s a limitation of the hardware or the drivers, but AMD cards cannot seem to support the entire hunk of software that the renderer needs to place in memory. They fill up and crash, and this is happening with both Cycles and Luxrender. I don’t know how Indigo Renderer is pulling it off, but it seems that they are using a variety of “tricks” to get rendering functional.
Long story short, Blender and AMD will undoubtedly play nice in the future, but for now, you need an Nvidia card.
You can try, best results is with the latest beta driver from AMD.
It is easy to test, look here:
http://www.blenderartists.org/forum/showthread.php?323594-Cycles-AMD-OpenCL-Test
Cheers, mib
I tried what mib2berlin suggested and, surprisingly, it worked. It is not as fast as i expected but it is well beyond the cpu performance, even though there are a few bugs that crash blender. So after testing it in a few scenes I decided that it is good enough for the type of rendering that I will be doing and since I don’t need anything super stable right now I will stay with my current 7970.
If you’re going to use your 7970, download a build of version 2.69. It is significantly faster than version 2.70 or 2.71.
OK, I’m using version 1.69 and it really is faster than the version I was previously using, so I’m changing the Thread to solved.