Lights don't become "IDL" lights. They stay what they are, except that IBL (Image Based Lights) behave differently when IDL is on. Spots, infinites, and points behave the same.

What changes is that everything is lit by everything else. Ultimately things are lit by the lights, but the secondary light from these lit things bounces around. Since this is a significant effect in real life, IDL helps a lot with realism.

The blotches are because the interpolation algorithm for the GI needed improvement. SR1 fixes this problem. They're very hard to get rid of with the initial release, unless you use some seriously ridiculous render settings, and then render time shoots through the roof. With SR1, quality settings can be decreased a lot, resulting in faster renders with better quality.

The image used in an IBL is effectively projected onto a gigantic sphere around your scene. This is the difference from earlier. Without IDL, IBL behaves like tiny area lights near everything, and is not blocked by walls and such. With IDL, IBL behaves like environmental lighting, but if you actually have an enclosed interior, with no windows or open doors or skylights, then the IBL does nothing at all.

That's why it is important to light an interior with light sources as would be found in real life. In a completely enclosed room, like a bathroom, if there are no light sources in the room, the room is dark.

If you surround your objects with a photo, such as when you use my environment sphere, there is no point in building an IBL for it. IBL is a cheat that enapsulates environmental lighting in an image, so you don't have to have an actual 3D environment. If you do have a 3D environment, or even a significant chunk of the environment, such as a backdrop, the light coming from this will be taken into account by IDL. And, by definition, the objects in your scene will experience matching lighting that corresponds with whatever forced imagery you've included around those objects.

P8 render times are much improved in SR1. However, anyything with transparency is slow in both. I've had a number of discussions with SM about why transparency is slow in Poser with raytracing of any kind, even in Poser 7 with transmapped hair. Try using ray-traced shadows with transmapped hair, and it takes forever.

We'll all have to keep telling SM that they have to find a way to speed that up. Poser figures need hair.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)