Path Tracing in low light areas ???

[pclavett]

I recently renewed with Terragen and have been learning lots of things ! I found the Path Tracer render that seems to markedly improve veggies in relative low light situations..... and just learned a few more things on this mode of render ! Today I posted a new image which was Path Tracing as a render and noted that whatever GI setting was inserted was not reflected in the render. After reading the documentation, it became clear that GI is simply not used in this mode.....certainly explained things ! The problem is....what do you do to improve lighting in these darker areas and still permit you to use the Path Tracer ? When I do the Standard Render, the lighting is more in tune with the GI settings that I wanted, but the plants are not as nice. My image this morning was very dark in the shadowy woods and in fact, almost black.......with some improvement when taken in photoshop and doing a generous shadows boosting. Think that what I want may not be possible but would appreciate suggestions if there are any that might improve my renders ! As always, appreciate all your help ! Take care !

[Hannes]

There are some possibilities. One thing people often do, is adding a second sun without shadows. I recently did something similar for some cloudscape, but I wouldn't recommend that, since it brightens up the image, but very often makes the lighting somehow flat. With the standard renderer you can increase the Environment light multiplier, but, as you wrote, this is not possible for the path tracer.
What you could try is creating a very large hollow hemisphere with normals pointing inside in another app and use this as an additional "skydome". It has to be "invisible" and set to not "cast shadows" in the Rendering tab of the object. Apply a white material to it with some self illumination. You have to do some tests how much you need. For a subtle effect it's probably less than 1. During the testing don't rely on the RTP. It won't show you the correct result. Do some small scale test renders, and you'll see, how it looks. It's a cheat, but I think, it's the best.

[pclavett]

Thank you so much for these suggestions ! Will see if some of these can help ! Appreciated !

[Dune]

I think a sky dome for lighting up is slower to render than an extra sun at small strength (0.5 or so) with no shadows (and just lighting terrain, not sky), but worth an experiment. I too find shadows often too dark, and sometimes increase the cloud cover (cirrus) if it's not visible for more reflected light.
It is also useful to have barks, branches and leaves to have some reflection, so more light is dispersed/reflected between them, so in the darks. And I don't know if that works for PT, but having leaves with a less than 100% opacity (0.8 or so, but always above 0.5) will keep shadows lighter. At least in RT it does.
And another option is to increase camera exposure to 1.5 or 2, and you can later adjust again in Photoshop or so. The latter also seems better for less grain in darks.

[Hannes]

Lots of possibilities. Yes, probably it takes more time to render with an additional sky dome, but it also depends on the size of it. If you have a smaller field of view, the skydome only needs to be as big as the part of the scene that needs to be brightened.
However, all this makes me think of creating a scene that needs to be lit up a bit and test all the possibilities and see which one looks best and of course compare render times as well. Now, that the Minerva contest will be over today, I'll maybe make one.

[Dune]

Good idea to do some experiments, I may do so as well, as the commissions have dried up a little.

[pclavett]

There was a useful discussion in the image sharing section about dark forest areas with the path tracer and several useful tips by Hannes and Dune...... so you may wish to look at this ! https://planetside.co.uk/forums/index.php/topic,30352.15.html