Global Illumination "Glow"

[Upon Infinity]

What GI settings could be used to achieve this effect?  Is it even possible?

[TheBadger]

I have not tried anything exactly like that. But I did find in things I have done with a similar idea, is that I could only get close by outputting an .exr And then doing post with the hdr. However, I do believe I remember seeing some image posts of test somewhat along these lines. But again not exactly like this in purpose.

DandelO did at least some work touching on the subject in the OP image. But the glow was not the focus of the effort as I remember it. You may want to shoot him a PM.

[jo]

Hi,

One way to get the glow is to use luminosity in the shader for the objects. In the attached images I increased luminosity to 10 for each sphere and made the luminosity and diffuse colours the same. The spheres are 1m radius. I didn't make any changes to the GI settings, this is using defaults.

Regards,

Jo

[Upon Infinity]

Thanks Jo.

I think that's along the lines of what I'm looking for.  I was confident that I could get something similar, if not exact.  I think that in earlier posts I may have underestimated Terragen's GI, as I was saying that it is not a true ray-tracer.  I think actually, it is more powerful than I gave it credit for.  However, the default settings in Terragen seem somewhat limiting in this regard.  For instance, when sliders will stop at 1, even though the program can be set higher than that.  I don't know if that should be tweaked at all, as I think I remember that coming up awhile ago, and that the sliders are set for realism.  Anyway, I'm confident I can get the effect I was after, so thanks.

Badger:  I might just do that if I need more guidance.  Thanks for the tip.

[Upon Infinity]

I do have a follow-up to this:  How do you get it to cast shadows of another imported object (that is not glowing)?

[Dune]

You could also try colored light sources inside the object(s); more glow possoble and more shadow. If you can make the objects so they don't throw shadows themselves, that is. But if they're glowing that shouldn't be a drawback.

[Oshyan]

The best way is to increase GI Cache Detail, but I think you may indeed be getting to the limits of the GI system. It's not really designed to excel at showing such complex, small-scale interactions. With high enough settings you can get decent results, but I can't help thinking that if this sort of close-up lighting interaction is key to what you're doing, it may not be so much of a landscape-type project, or at least you may need to accept some compromises.

In the attached images, I used GI Gache Detail of 2 (default), 5, and 10. You can see the result with 10 is not bad, but render times will be very high for a scene with any real complexity.

- Oshyan

[jo]

Hi,

I think that's along the lines of what I'm looking for.  I was confident that I could get something similar, if not exact.  I think that in earlier posts I may have underestimated Terragen's GI, as I was saying that it is not a true ray-tracer.

Well, for GI purposes it's a "true enough" raytracer. TG traces rays for the things which need it, such as GI, shadows and reflections.

However, the default settings in Terragen seem somewhat limiting in this regard.  For instance, when sliders will stop at 1, even though the program can be set higher than that.  I don't know if that should be tweaked at all, as I think I remember that coming up awhile ago, and that the sliders are set for realism.

The general idea is that sliders are set to the values that are reasonable and to make it convenient to work with "normal" values, but with pretty much everything in TG you can enter larger or smaller numbers if you want to push things. We deliberately allow this to let people experiment with things if they want.

Regards,

Jo

[Upon Infinity]

Thanks guys.  I think, armed with this, I'll be able to at least achieve acceptable results.  Anything from a doubling to a quadrupling of render time is acceptable for the few times I might need to do this.

Ulco:  I might try that too, I hadn't thought of it.

[Upon Infinity]

It works!  Well, sort of.  It blocks light well enough, but I have those weird divots on the left where nothing is blocking the "light".  I suppose this'll have to do.  And really, only the detail obsessed (me) will notice.

[Oshyan]

It looks like it's emitting light from each face of the faceted object. It's not a terribly accurate representation perhaps, but I would guess it's occurring due to the faceting of your emissive object. If you use a more "normal" object in your real scene you shouldn't see such obvious inaccuracies.

- Oshyan

[bobbystahr]

Here's a solution I just did a Quik an Dirty test of.

[Matt]

It works!  Well, sort of.  It blocks light well enough, but I have those weird divots on the left where nothing is blocking the "light".  I suppose this'll have to do.  And really, only the detail obsessed (me) will notice.

Yeah, it doesn't look quite right. I wonder if this is affected by "GI sample quality".

Matt

[bobbystahr]

I re visited the hexproject I have up at the other thread with the updated program and am much pleased with the result. Bounce to the ounce is largely responsible but I put a spotlight 20 m. down under the ground and I haven't done a control but think that's also contributing but there is no  actual light other than the spotlight.

[Upon Infinity]

Not bad, bobby!  Try turning one dark to see how well it blocks the light.