Difference between sunlight and Light source

[mt_sabao]

Hei guys,
Is there any difference between sunlight and a Light source. The reason i ask this is because i wanna have a composition sorta like the image below



where the three planets in the background (the small spheres) should be "behind" the star (the white sphere), otherwise they wouldn't be illuminated. So i guess that this is impossible because the sunlight is in infinity right? So i figured i could use a light source instead, set at the correct distance, and at with extremely high strength values. SO, getting back to the question, will there be any major difference on the way my planet will be illuminated, is there something I should take into account? Or, is that any other way to achieve this that i'm failing to see? The really major pain I see, is that the light can only be placed using x,y,z coordinates, no heading, distance, elevation :S

Thanks in advance guys!
Luis

[PG]

Light sources are, I'm pretty sure, very localised sources of light. It's quite difficult to achieve the same soft light that the sun gives off with a light source. You either end up with the light being too weak to light the surface you want it too or you just end up with a big colour ball in the middle of your scene. This only applies to scenes of this scale though, for scenes close to the ground light sources are fine.

[mt_sabao]

hmm, i dunno, that's why i ask. The sun is a light source with parallel rays, in "infinity". Light source is an omnidirectional light which at a very far distance rays start becoming parallel. I'm trying with a light source at 1e+08 and a strength of 3e+16 and the difference is not exactly obvious. Well, at least from the quick render and and nothing but the default planet...

[mt_sabao]

Look the image below, left sunlight, right light object. The intensity is not exactly the same, but the overall look is not different. hmm

[mt_sabao]

ugh...actually from the surface this is how it looks, with light



and how it normally looks with sunlight

[PG]

haha. bet vue can't do anything as realistic as that
Here's a sunrise with sunlight v light source also with their render times to show you the difference. I didn't tweak the light source one to look exactly like the sunlight but you can easily do it.

Sunlight 6:01
Light source 5:29

EDIT: I redid the light source one, just lowered the altitude on the light source to get a more similar colour.

Here's the TGD...if it'll fit

[mt_sabao]

Hmm, so you're getting the same results? Why am I getting such different results (as in the last two images)? Nice image btw, and thanks for sharing

[PG]

Well I'm guessing you have created a light source with an insanely large radius. I've created one with a very high value colour. I set the colour to 50 in this particular image. Have a look at the difference between your light source and mine.

[Mohawk20]

I recently discovered that the sun is actually a light source itself. Just zoom out until you can see the background object sphere. The sun object is inside it...

[PG]

wha? the sun is a light emitting object and as you said yourself, the background object is just an inverted sphere and the sun can't be on that so it has to be an object of some sort, yet I see nothing that suggests that the sun is actually the same type of light emitting object as a light source.

[Tangled-Universe]

Mohawk is correct.
Both lightsource and sun are "point lights".

Martin

[Mr_Lamppost]

Without seeing your .tgd I'm not sure why you are getting that strange result.  It is certainly possible to use a light source in place of the sun.  The composition you are looking to create should certainly be possible however; You may need to increase the size of the universe (Background object), to fit it all in, consider placing the light source at the origin and then moving both the camera and main planet well away from it.  You nay also have to give the lightsource an insane intensity in the tens of millions and a huge radius if you want to generate soft shadows. 

Sorry I'm in the middle of something else so can't make a test / example at the moment.

[mt_sabao]

Without seeing your .tgd I'm not sure why you are getting that strange result.  It is certainly possible to use a light source in place of the sun.  The composition you are looking to create should certainly be possible however; You may need to increase the size of the universe (Background object), to fit it all in, consider placing the light source at the origin and then moving both the camera and main planet well away from it.  You nay also have to give the lightsource an insane intensity in the tens of millions and a huge radius if you want to generate soft shadows. 

Sorry I'm in the middle of something else so can't make a test / example at the moment.

Thanks guys for the help!
great then, this is all I needed to know then. I guess it's just a matter then of playing around with the intensity and radius. Cool.
Now the problem is that I have no spherical coordinates, so placing this light exactly where I want it to is gonna take some patience. Hmm, in Cinema4D I could easily come up with an expression...    

[mt_sabao]

ugh...actually from the surface this is how it looks, with light

interesting, just tested it now with a Light Source, distance 1e+08, intensity 3e+16 (same as above) but changed the source radius from 0 (above) to 1000 (below) and it fixed it. So, given a certain distance, Strength and source radius, Light Source = SunLight.

[Matt]

The Sunlight is a bit different because it will appear to 'follow' the camera even if you move it over large distances. Or at least it does in 2.0 now that alignment problem has been fixed. You will always be fighting with large number to get the same effect with a Light Source. In this kind of planetary system it's probably what you need though.

Matt