Odd render time question

bobety316_c50224ad1f

I render with iray in ultra HD with a 3060 nvidia card and I get what looks like a great image after a minute or two. However I usually let it render for over ten minutes and to be honest I don't see a lot of difference in the finished result between the two. 

Can anyone explain what's going on with the render the longer I leave it and is there a quality going on that i'm not noticing?

 

Many thanks.

Richard Haseltine

Engines like Iray don't ever finish, they keep firing light paths into the scene, following them through to a final value, and combining that with the existing value for the affected pixel to get progressively better estimates of the "true" value. The default stop condition for a render, assuming ti has enough time and iterations (samples), is 95% convergence at Render  Quality 1 - convergence is looking at the number of pixels that seem to have settled on a value, and render quality is how narrowly defined that settlement is. It is quite possible for an image to look good enough even though there is enough variation in enough pixels for iray to keep going, and if it reaches that point you can cancel. Conversely it is quite possible for a smal but noticeable area (eyes are often a problem) to still look very noisy but for them to account for a smal enough proportion of the pixels that Iray will stop (in which case doing spot renders of the problem areas to a new window and layering them on the main render can help).

bobety316_c50224ad1f

Richard Haseltine said:

Engines like Iray don't ever finish, they keep firing light paths into the scene, following them through to a final value, and combining that with the existing value for the affected pixel to get progressively better estimates of the "true" value. The default stop condition for a render, assuming ti has enough time and iterations (samples), is 95% convergence at Render  Quality 1 - convergence is looking at the number of pixels that seem to have settled on a value, and render quality is how narrowly defined that settlement is. It is quite possible for an image to look good enough even though there is enough variation in enough pixels for iray to keep going, and if it reaches that point you can cancel. Conversely it is quite possible for a smal but noticeable area (eyes are often a problem) to still look very noisy but for them to account for a smal enough proportion of the pixels that Iray will stop (in which case doing spot renders of the problem areas to a new window and layering them on the main render can help).

Thank you for such a detailed response :)

Is basically what you're saying, if it looks good enough then I can stop the render?

Richard Haseltine

bobety316_c50224ad1f said:

Richard Haseltine said:

Engines like Iray don't ever finish, they keep firing light paths into the scene, following them through to a final value, and combining that with the existing value for the affected pixel to get progressively better estimates of the "true" value. The default stop condition for a render, assuming ti has enough time and iterations (samples), is 95% convergence at Render  Quality 1 - convergence is looking at the number of pixels that seem to have settled on a value, and render quality is how narrowly defined that settlement is. It is quite possible for an image to look good enough even though there is enough variation in enough pixels for iray to keep going, and if it reaches that point you can cancel. Conversely it is quite possible for a smal but noticeable area (eyes are often a problem) to still look very noisy but for them to account for a smal enough proportion of the pixels that Iray will stop (in which case doing spot renders of the problem areas to a new window and layering them on the main render can help).

Thank you for such a detailed response :)

Is basically what you're saying, if it looks good enough then I can stop the render?

Yes.