Hi Nates, I never said it was Cycles that was doing it.
When I first reported the issue I did not experience this while rendering but simply using Rhino. Opening a huge model and using rhino Array command. It is definitely a Rhino performance issue. Raytraced is behaving as expected.
I started using Blender because they added Cycles. I couldn’t be more happy about seeing it in Rhino too. 
For the first 20 samples you’ll see increased CPU usage. This is where Rhino copies the Raytraced results to the render window. After the render window will be updated only every 20th sample and you should only a CPU spike then. Raytraced is fast, but unfortunately copying of its results through the hoops and loops necessary to get it from GPU through .NET managed world into the unmanaged render window world of C++ is not helping much. I hope we can make this much faster in the future.
Rhino Render Next is only a work name. In v7 it will eventually become just Rhino Render - the replacement engine of the V6 Rhino Render (:
Hi guys, I am batteling with Cycles on a project that has a few large meshes with large textures on them and it takes a looong time (20 seconds) for Raytraced display mode to fire up. I don’t understand why it should take so long to read three images, nor to upload them to the vram, at least not since OpenGL never takes a second to think, so please explain again if you like.
But the really annoying thing is that when I run ViewCaptureToFile then it stays idle for another 21 seconds, before showing the dialog! I presume it is because it has a silly idea of calculating the tumbnail from scratch, so it has to reupload those images or something… Please look into that, because we all hate to stare at blank screens with out any indication of progress when we are close to deadlines… 
Until the preview rendering has been improved perhaps just use the -_ViewCaptureToFile command so you don’t have to wait for any of the preview rendering.
Can you share your file with me on rhino3d.com/upload with nathan@mcneel.com as the recipient? Do ensure all texture files are saved with the 3dm. I can have a look to see what the reason is for the pain.
Sure thang, I’ll zip it up and send you a link.
File uploaded, shout if you need any assistance and I’m eager to know if anything can be done to speed it up right now (other than resizing the images etc). Cheers
