Quick question about I Ray

deeahr2169

Ok having ignored iray for ages because I didnt think a mac with no Nvidea could use it, i have discovered that I can. The results are better than I expected but I have a couple of questions that will possibly seem stupid, but here goes anyway....It seems to me that when I have a IR scene in my viewport it changes as I watch, and if I change something then that change happens as I watch although it of course takes longer.

So if I then render that viewport image I am assuming that the render captures what is happening in my viewport at that moment, and then does that render continue to change and improve in quality?

Again my assumption is that once that render is saved, then I can render the same image again with perhaps some changes made and the new render will incorporate those changes. Am I right?

Richard Haseltine

The Viewport Drawstyle and the render are not related - they can have different properties, in Draw Settings and Render Settings respectively, so it wouldn't make sense to pass the one over to the other in most cases. Iray uses path tracing - it sends out a path from a soruce and tracks how it bounces around the scene until it stops, then feeds the colour that results into the pixels on the bounce points (roughly). As more and more paths contacts accumulate on a pixel it gets closer and closer to its "final" value - that is why the drawstyle and the render keep changing, and why a render which is stopped early or which has visible areas thata re hard for light to reach will look noisy.

deeahr2169

well for a less than techno user that was a lot to try and absorb. I honestly appreciate your assuming that I might follow all of that, but the truth is I was hoping for an answer in primary school English, still you have forced me to act my age at least. If I have the gist of this the longer I leave it the better its going to be, at least in quality...

That may sound tetchy but honestly, its a real plus when someone with obvious knowledge doesnt treat those less able like dimwits...

Very much appreciated Richard

Handspan Studios

Yes you have render settings under "render quality" you can set that number to 1.0 or more/less and also render %, you can tell it to always stop at 95% or go to 100. You have to decide where it looks good enough versus how long it takes to complete. Texture filtering is a setting that can make a difference to how crisp the details are without making you wait longer, a lower number than the default, around.50 instead of 1.5 any lower and it looks too sharp. If you get spots and dots make sure the firefly filter is on. A lot to remember but worth it, I think.

I struggled with a PC gpu that wasn't up to Iray for a while, I symapthize.

onix

Your question is not absolutely clear, but if I understand it right every time you change anything in the sense it all gets reset and started from zero. If the scene doe not changes the raytracing process continues for a while and quality increases gradually.

if you save a picture you cannot even continue rendering it. The new render will start from the blank page.

Rendering without GPU is a bit unpleasant but if you use AI denoiser you can get pretty good results in relatively short time. You can render a scene in about 10-30 minutes even on the CPU

 

 

 

 

 

 

chris-2599934

deeahr2169 said:

It seems to me that when I have a IR scene in my viewport it changes as I watch, and if I change something then that change happens as I watch although it of course takes longer.

If you set your viewport mode to "NVIDIA Iray," Daz gives you a preview of what your finished iray render will look like. However, if you don't have the necessary hardware to render Iray quickly, it can be a pretty painful process (it can still be awkward even with an nVidia card in your rig). Fortunately the mode which you use in your viewport has no bearing on your final render, so you can use something quicker most, or all, of the time. I suggest setting it to "Texture Shaded" most of the time, and only switch to Iray when you want to do stuff like fix the lighting, or see what a texture looks like.

So if I then render that viewport image I am assuming that the render captures what is happening in my viewport at that moment, and then does that render continue to change and improve in quality?

When you hit the render button, the software starts rendering what can be seen through the current camera, progressively improving the image in a series of passes called "samples."  It's important to realise that an Iray render is never really finished. If left to its own devices, iray will carry on polishing and refining the render forever. What stops it is a set of settings in the "Progressive Rendering" area of your Render Settings tab. There's "Max Samples" - the maximum number of cycles the renderer will go through. It defaults to 5000, which should be plenty. There's "Max Time" - the maximum time the render will take (in seconds). This one defaults to 2 hours, which almost certainly not be long enough with your hardware - I suggest you set it to 0, which means it will be ignored. The last, and most important one is "Rendering Converged Ratio," which very very loosely equates to how complete the render is, leave this one at 95%. Now you can set your render running and go and do something else while it works away at the image.

Note that you can come along at any time, decide you're happy with the image as it is now, and stop the render process regardless of how converged it might be. If it looks OK to the mark 1 human eyeball, what else are you going to look at it with?

Again my assumption is that once that render is saved, then I can render the same image again with perhaps some changes made and the new render will incorporate those changes. Am I right?

There's two different things to save. When you've completed a render, you can save the result as an image file - usually a png or a jpg. You can deal with that as you can any other picture, but it doesn't contain any real information about hoe the render was set up. The other thing you can save is the scene, from the File menu or by pressing Cmd-S, which saves all the information about your scene in a .duf file. This is the file that you can open again later, make changes to, and produce further renders. I would suggest always saving your scene before you start a render, because renders can crash and you don't want to lose your work.

One thing to note about saving scenes: if you're using the "Perspective View" in the viewport to line up your shot, it won't be saved in the scene. You need to create a camera in the Create menu and use that instead. Note that one of the options when you create a camera is to copy the currently active view, so you can do that to put it in the right place.

deeahr2169

I forgot I had asked this question so apologise for having taken so long to reply to the excellent and comprehensive answer from Chris. Just exactly what I needed, an answer that takes the question step by step and answer each in clear and concise, and most importantly understandabe language. I have always thought that Iray was prohibited to me because I am a Mac user, but thats not the case, as I have found out recently by trial and error. My render preference was Reality 4, which still gives some outstanding results in my opinion despite the fact that it is almost as elderly as myself. The results I have achieved using Iray have been every bit as good as with Reality, maybe better, because one can always leave the thing rendering as you can with Reality though my patience is lacking. 

Motto. stick it in the oven and let it cook, you never know what will come out...

Many thans to you Chris for some top notch help and advice withour frills....