Spot Render Tool isn't faster than full render. (SOLVED)
Etheral
Posts: 91
So I tried to use spot render tool to re-render small parts of my image with small fixes I make and I overlay these on top in photoshop (I changed the spot render to render to window in the tool settings). But I noticed that my render speed is the same whether I render the full image or just the small piece. Did anyone else ever have this problem? I used to do this sort of thing in 3DS Max all the time and it worked as expected. I'm rendering in IRAY on a GTX980ti. The image is 3840x2160 resolution but the piece I try to spot render is much much smaller than that. Maybe 400x200 or so. I'd really appreciate it if someone can help since this sort of functionality is very important to me.
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Comments
It may be that the piece you are rendering is a difficult area - lots of reflective surfaces or mostly indirectly lit perhaps.
The lighting is just simple dome lighting and very well lit. It's not like it takes all that long to render. The full 3840x2160 render takes 12 minutes. The tiny spot render piece is taking 12 minutes also.
That is odd. Theer will be the time to load the scene into the GPU, which is unaffected by the area you are going to render, but I doubt it's taking 1 1/2 minutes to load and a minute to render.
There are two phases in an Iray render: scene collection and actual rendering. The first part will take the same amount of time regardless of whether it's a full or partial render. In this phase, D|S prepares everything for the render, including converting any shaders to iray-compatable, and ships off the scene to Iray. Dureing this phase the render summary will be stuck on Rendering... The second phase Iray begins actually to render the scene.
You can shorten the amount of time needed for scene collection by doing a full render into a new window. Just start the render until the first image forms, and cancel. Keep the window open -- the scene will stay in memory. From there, the spot renders should be faster, because the same scene database will be used. Note: the database is rebuilt if you add or remove geometry or textures, though I'm not sure if it gets rebuilt from scratch.
The problem fixed itself. No idea what was wrong but restarting DAZ and doing the same spot render converges much faster now.
This is helpful, thanks. I didn't realise keeping the window open makes the scene stay in memory.
For your first comment, there may have been an issue with temp files. I frequently (several times a day) restart D|S, just out of habit.
For tidbits like the scene database, it helps to have a performance monitor (Task Manager will work if you're running Windows), and you can see what memory is being used up. As long as that render output window is open, all kinds of RAM is held up. Close the window, and after a few moments the RAM goes back down. You can get similar useful information about what's going on with a GPU monitor.
Okay I found what causes this problem and was able to replicate it over and over. When using spot render tool, make sure the viewport mode isn't set to iray. If the viewport is set to iray, using the spot render tool will cause the spot to render at the same speed as the full image even though it opens in a new window and renders just the small segment. Just leaving this comment here to let any future readers know the cause of the problem.
OH MY GOD. I can't believe this bug exists in Daz Studio. I just tested it. When I turned off IRAY in the viewport, the spot render speed on the same section of the face went from 24 minutes to 3 minutes & 40 seconds.
Guys, we need to inform DAZ of this MAJOR bug.
As I said in your other thread, this is not a bug.
@liplin901 "Guys, we need to inform DAZ of this MAJOR bug."
If the Viewport is set to Iray, there is no reason to use Spot Render (you know, since the whole Viewport is rendered?????).
He's using Spot render to a new window to get a clean render of areas that aren't converging in a normal render, that's a common technique.
I would bet it's not a common technique if the viewport is set to Iray (since we haven't seen this specific compliant before). How is a spot render going to converge an area that isn't converged in a full render?
But, whatever. These issues go away once a user understand how light behaves in the real world.
Convergence threshold is based on tne percentage of pixels converged. If you have a small problem area (e.g. the eyes) then it's likely that enough pixels in the rest of the image will be converged to terminate the render while the area is still very noisy. Doing a spot render enclosing the problem area as tightly as possible means it accounts for a much higher proportion of the active render, and so should be much closer to fully converged when the end condition is reached. Then the spot render (if done to a new window, so it aligns with the full render) can be dropped on top of the noisy area of the full render.