Render issue - any ideas???

AdrianS

As I have a fairly hi-spec machine with an NVidea graphics card, I normally render at a fairly large size (around 2500 x 1700 pixels, with the DAZ high quality render settings from Render presets). A render of a figure normally takes 20-30 minutes. I recently set up a scene of a single figure ('From Russia - Sventlana, plus hair, necklace and earrings) at those settings. After 5 hours, the render still said 0%! I abandoned it and saved the scene. I ticked the Optix Acceleration box, reset the render settings to default (but increased the size, the max samples and the max time) and tried again. The render has now been running for just over 24 hours and is at 88%. What could be causing this to take so very long? Two other things related to this puzzle me. When I tried to increase the maximum samples, I  can normally increase it to maximum easily. This time, it was like pulling the dial through treacle, and a small movement seemed to increase the max samples more rapidly than usual. The other thing is shown by the attached image. This is the render I saved from the first time, at a point when the render said it was 0% complete - not bad for 0%! Can anyone come up with any ideas what is going on here?

tring01

Suggest the following:

Make double sure that you have current IRay compatible shaders on everything in the scene, espeically anything that has transparency (like hair).  If you're not sure if the shader is IRay compatible you can just apply the IRay Uber Base to it.  That should make it at least compatible with IRay.

If your scene is lit by any emmissive lights make sure they are simple planes with only one division - and leave two sided light off.  Just make sure you have the correct side pointed at your scene.  If you have emissive surfaces that are just glowing (not lighting the scene), you can leave those with complex geometry.

I've found that transparent shaders (especially glass shaders of any kind), and highly reflective shaders (like polished marble), will increase render time several orders of magnitude.  I wouldn't be surprised if that's your issue.  This one is tougher to resolve if you have your heart set on the transparent or reflective objects in the scene.  You can help this along by turning off any objects not in view of your camera.  Be careful though that you don't turn off somthing that you want to show on one of your reflected surfaces.

Another thing to consider with transparent and reflective objects in IRay is that they will take 10 to 100 times longer to render - but you really aren't often gaining much image quality in most of that render time.  The solid objects might all be rendered really well, but IRay still tells you you're at 0% convergence because it's trapped fiddling with the reflecting and refracting ray traces through and against your transparent or reflective objects.  You may only need to take the render to 2% or 5% convergence to get a good enough result.  The only way to determine this is by trial and error.

Good luck!

fastbike1

You know you can double click on the numeric value and just type it in, right?

For closeups, hair will have a big impact on render time. Check if the sub-D level is high (3+). You also may not need "high quality" settings to get a great render. The "Render Quality setting (1,2,3 etc) causes a roughly factor increase in render time (e.g. 2 twice as longe, 3 3 times as long).

Finally, you don't say what Nvidia card. It's possible that your render won't fit in Vram and so defaults to CPU render.

I have a GTX 980TI and I could typically render your example at 2000x 3000 in about 45 minutes. Lighting will also matter. Mesh Lights are typically much slower if they have much geometry involved (more than a simple plane).