Why are these white things in my coffee?

odastein

So, I bought some set that includes cups of coffee. However, there are little white dots at the surface of the coffee (see picture). What can cause that, and how to change it?

 

Thanks in advance.

Richard Haseltine

Noise, where the render hasn't finished converging (assuming this is Iray). There's more noise in othe rparts of your image. Are you using the default render settings? Have you added extra lights?

odastein

In fact, although the image I uploaded is taken from the main windows of Daz 3D (can't remember its name) in Iray mode, the rendered version still had a lod of these white spots, but only in the coffee (I'm uploading the rendered version of the cup).

Yes, I think I still have the default settings, and I didn't have this problem with any other object in any other image previously, but indeed, this render was quite quick. I believe you can change the number of "iterations"? Maybe I should do that?

Watching this image more closely, I also have some more discreet white dots on the table and the saucer to the right of the coffee cup, in the shadow, in fact. I see no other in the rest of the image, including on other dark elements, just in this little corner, for some reason.

And no, I didn't add any light. I'm yet to learn how to use them.

Richard Haseltine

It may be that most of the image converged (that is, essentially, stopped chnaging with additional iterations) quite quickly. if a relatively small area is much slower to converge it can end up still being very noisy when the render finishes (by default, 95% of the pixels need to be converged).

• You can increase the convergence ratio 9ask for more pixels to be done) or you can set a higher quality (the render will wait longer before declaring any given pixel done), either of which may allow the still noisy pixels to at least be less noisy.
• You can switch to the Spot render tool (Tools menu) and in the Tool Settings pane select teh new Window option, then drag out a rectangle over the problem areas (because they make up a higher proportion of the render that way the whole area should be closer to done when the render stops, but you don't have to wait on all the other areas) then save as PNG or tiff (to have a mask) and composite that on top of the main render in your image editor.
• You can render twice as large as you need, assuming you need no more than 5,000 pixels per side, then downsample in your image editor to average the noise out.
• If you are using the DS Public beta you can try the new Denoiser, though the render has to fit into the GPU for that

odastein

Thank you. Very informative about how image rendering works.

dracorn

Check your cream.  It's probably past the expiration date.

=o)