Why is my IRAY render not calculcating any convergence?

Flortale

I have Genesis 8 in a scene with some hair. When I'm zoomed out, where her whole body is in the camera view, it takes about 4 minutes to render and convergence begins calculating a 1 minute and 30 seconds in.

Now I'm doing a close up render of her face.  It's been going for 15 minutes now and hasn't calculated any convergence yet. The render looks crisp & sharp, no fireflies. 

Does IRAY sometiems fail to calculate convergence and then the render just runs until the max samples is reached?

Update: IT FINALLY calculcated convergence at 17 minutes in.  Convergence is at 3% and slowly rising.

Update again: [what is happening]? I moved the camera angle a little bit and the convergence calculated in a minute and a half.

JonnyRay

Complex skin or hair shaders can make Iray take a long time to calculate convergence (even though you don't see a lot of changes in the scene). My last one took about the same as yours 15-20 minutes. Changing a camera angle will change the angles of the light paths and can therefore significantly affect how the engine calculates the convergence, etc.

Richard Haseltine

What do you mean by calculating convergence? Showing progress on the bar? That means that at least soem pixels are converging, not that it hasn't been calculating. Stuff with high-frequency detail, like hair and some skin, takes longer to meet the criterion for convergence - when you zoomed in you increased the amount of the image area that had that kind of content.