Speckling Issue

masterharper64

Can anyone help?

When rendering (IRay), I am getting speckling on certain areas of an image, especially eyes and in close-up images. I have tried playing around with the render settings and have seen a little improvement, but not to any great degree. Is it possible that this could be being caused by the limitations of my graphics card which, at the moment, is an ancient NVidia GeForce GT520 with 1Gb GDDR3 RAM or does anyone have any other suggestions as to what may be causing this?

Togire

It definitely cannot be caused by your graphic card. The only difference between cards will be 1/ the complexity of the scene that can be handled and 2/ the computing time, but besides that the results should be identical.

Maybe if you post a render it will be easier to identify the problem.

margrave

Speckling has any number of issues, but generally it's because a surface is either too shiny or there's not enough light. If a material has too much specularity, it produces hot pixels where the light intensity clips. If there's not enough illumination, then Iray can't do the shading calculations propertly and there's a lot of noise.

Pictures would help.

PerttiA

It is a sign that your renders have stopped too soon.

In your case the rendering is done on CPU and the GPU has nothing to do with it.

Set Max Samples and Max Time in rendering settings to either -1 or 30000 to let the rendering have the time it needs.

Richard Haseltine

Eyes can be much slower to converge (reach a state that Iray counts as finished) than many other surfaces. Shadowy noks and corners can also be slow, as they rely on light bouncing in. If most of the image looks done the render may have stopped as Iray thinks it is close enough (the Convergence Threshold setting). There are a free things you can try, though they will all add to the total render time:

• increase the convergence threshold - this may mean that the problem areas are now a large enough proportion of the image that their lack of convergence is taken into account, and the render will continue until at least soem parts register as converged - at which point, potentially, the rest will at least be fairly close
• use the denoiser, as long as you are able to render with your GPU (it isn't supported in CPU renders) or use a post-render denoiser
• increase the render quality setting - this makes Iray fussier about what it counts as converged, so by the time it is satisfied with the easier sections the tricky areas may be more nearly done and acceptable
• activate the Spot render tool, in Tool Settings set it to render to a new window, and drag a rectangle around the problem areas - again, this makes the problem area a larger part of the image and so forces Iray to pay attention to it. Once done save as Tiff or PNG and you can just add the spot render on top of the main render to patch the noisy area.