I don't know what's going on. But I'm have issues with Cycles, not rendering as it should. First it was taking up to 2 hours to render a very simple frame at 300 Samples (think semi reflective box on a dull plane and one sun lamp). And now I test a render and it's coming out as absolute rubbish, no matter how igh I put the sample count. The Preview render is looking 10 times better! Oh and before, that same 2 hour render at 300 samples was rendering in the 3D port at 300 Samples in 7 minutes! Why does the actual render take 2 bloody hours?!

Plus I can't seem to figure out how to access my computer's GPU rendering option.
Here's a unlisted video to show what I'm talking about...well part of what I'm talking about.
Here's the video:
http://youtu.be/ZtuDKN67BHM

http://youtu.be/ZtuDKN67BHM

The Cycles renderer takes advantage of the GPU, but it has to be an NVidia graphics card running CUDA, and a reasonably recent graphics card at that. For example, I have an NVidia graphics system with CUDA installed on my laptop, but it's too old to actually work.

If you do have an NVidia card with CUDA cores, you need to:

-- download and install the CUDA driver for your OS
-- in Blender, under User Preferences -> System Tab, for Compute Device select CUDA and your GPU
-- in your scene, when rendering, under Device, select GPU Compute
-- at the top of the screen, make sure the Cycles render engine is selected (Cycles Render) and not Blender Render 

You might also look at your materials. Cycles uses nodes to define materials.

Everything Robyns has said above is correct but you must make sure that if you do have a NVidia card that it is a supported GPU rendering with NVidia graphics cards. We support graphics cards starting from GTX 4xx (computing capability 2.0). My particular card which is NVidia but is only 1.0 so when I render with Cycles it will use the CPU instead of GPU so render times will be longer you can find a list of supported cards at this Link so you can see if your card is one of them https://developer.nvidia.com/cuda-gpus  

 

 

 

is there an inner cylinder inside teh tube or is it supposed to be a solid piece like glass?

start with the volume samples because of the opague materials and check the nodes to make sure they dont have a noise or roughness setting that isnt supposed to be there

as for why the actual render takes longer its because there is a hell of a lot more information to process than in a preview

 Thanks for the info, everyone. I'll look into it.
(PS: That sucks)

unbroken,
This example is currently solid. The final will have a inner (and thinner) tube that will be a emission light. Works very well for creating a realistic Neon Sign.

 My issue is that the render (no matter how much I jack up the samples, looks waaaaaay worse then the actual preview. And it's rendering much faster then the preview at the same sample setting.

 In the image and video, the one on the LEFT is the render, and the right is the preview. This is my issue. And it only seems tp be doing it with this file.

I'd almost be willing to bet the sample settings under the render layers for your scene is overriding the total samples under your overall render settings.

Why that guess? The layer samples box is active under your samples settings.

Go back to the scene settings and set samples for your layers to 0 (use main settings for each layer), and try giving it another shot.