I think I'm going crazy...

morrisonmp

So. This is what confuses me and drives me nuts about Daz. 

I have a scene I've built. It's got a house, a lawn, a fence, road, trees, etc. Inside the house (which is otherwise empty) is a dining table and two chairs. I added a primitive (plane) to create a light source in the dining room.

Camera showing the outside of the house/all geometry turned on: less than 3 minutes to render at UltraHD.

Camera showing the dining room/some outside geometry turned off: 35+ minutes and it hangs up at about 36% finished and even though it is still iterating, it just... seems like it's going to take forever.

Why? Why is it so different? What is happening?

3141592654

Hmmmm ... it could be a lot of things ... but a couple come to mind first. First, darker places like interiors tend to take longer.  Second, adding a primitive light should not add that much time, but to be sure do a few minutes of render with that light turned off. Sometimes a single object like a mirror can add a tremendous amount of time to an entire scene ... perhaps your table and chairs have glossy / surface settings that are adding a lot. Try a few minutes of render without the table and chairs.  If you find the object(s) that are taking a huge amount of time, then you can change those settings.

I repeat, seriously, I have had many scenes where a single object made all the difference in rendering speed. Reflection and refraction are big culprits for this.

Richard Haseltine

Yes, it is probably the lighting (though if there are a lot of shiny surfaces that could be a factor, as the light paths bounce around inside the room instead of being able to escape to inifinity as they can outside). A single light source, whether a plane or the HDR shing in through the window, won't directly reach a lot of areas so you are relying on light bouncing off other surfaces - possibly several times - to reach those places, and that is going to take a lot more iterations to settle on a stable value than light shining from every directuin with the outside lit by the HDR from all around.

Chezjuan

One reason is that Iray has to calculate the light paths, and inside a structure there are a lot more things with which light will interact. Even if there isn't a mirror, light rays can bounce off walls, the floor, the table, etc. Because you're in a finite space, a single light ray can bounce around quite a bit before it gets to the point where Iray decides it's in the right place to call it "converged."

Outside, being for all practical purposes an infinite space, means that many of the light rays can be "written off" so to speak because they head in a direction that will never end up in the image. I have also found that spaces with a lot of windows can render faster than a similar space with few windows, again because the light has a place to go where Iray can decide it's not going to end up on a pixel in your image.

 

morrisonmp

Update: So, I removed the emissive plane and instead put in a point let (set to sphere). I used the same lighting settings otherwise. Everything else stayed the same. 

It actually rendered without hanging in about 45 minutes - still long but not unexpectedly so. 

Thanks for the suggestions.

Taoz

Alternatively you can use an Iray Section Plane to make one of the walls transparent (or just hide the wall if possible), this way you can use the external light.