Dawn or Dusk???

Marcos Silveira · April 10, 2009, 08:22:51 PM

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Luminos · April 11, 2009, 03:11:28 AM

dawn

Marcos Silveira · April 11, 2009, 07:11:24 AM

Quote from: Luminos on April 11, 2009, 03:11:28 AM
dawn

I always thought about it... Is there really a difference?!?! Becouse both are just the sun in a position relative to the horizon... I think it's the same index of luminosity interacting with the landscape.
If You think different please, explain it to me.

Tangled-Universe · April 11, 2009, 07:25:18 AM

Dawn is in the morning, Dusk in the evening...I'd say this is dusk...no, dawn....well, no, ehhrr...whatever

The lighting at the underside is quite nice in some areas.
What happens if you increase the contrast in the renderer to ~0.55 and gamma to ~2.5?

Martin

sjefen · April 11, 2009, 08:49:41 AM

I'd say dawn.

Although I don't know the difference, I'm pretty sure there is one.
Maybe it has something to do with with the sun warming up the atmosphere the whole day and when it goes down it is more red for example. I don't know.

Nice image anyway

- Terje

Tangled-Universe · April 11, 2009, 08:53:50 AM

Technically they should be the same. In both cases the red at the horizon is being caused by redshift. The lower the sun is at the horizon the more atmosphere the light passes through due to it's low angle. This causes many light to be broken by particles etc. etc. and results in energy-loss and thus shifting of the lightspectrum to red.

Both happens in dawn and dusk.

The reason that it appears to be more red at dusk could maybe because of there's more haze at dawn?

Mohawk20 · April 11, 2009, 08:58:22 AM

The difference between dawn and dusk is probably the temperature of the air, affecting the refraction index. At dawn, the air is still cool, while at dusk the air would be warmer from 16 hours of exposure to the sun.

The warmer air might reflect the red colour from higher up in the sky, so at dusk the sky has more red in it, while dawn has more cold colours like yellowish reds. And some hazy whiteness as TU suggested.

Marcos Silveira · April 11, 2009, 09:02:12 AM

Quote from: Mohawk20 on April 11, 2009, 08:58:22 AM
The difference between dawn and dusk is probably the temperature of the air, affecting the refraction index. At dawn, the air is still cool, while at dusk the air would be warmer from 16 hours of exposure to the sun.

Well, i'd say it's a reasonable explaining...

Tangled-Universe · April 11, 2009, 09:06:02 AM

Quote from: Mohawk20 on April 11, 2009, 08:58:22 AM
The difference between dawn and dusk is probably the temperature of the air, affecting the refraction index. At dawn, the air is still cool, while at dusk the air would be warmer from 16 hours of exposure to the sun.

True.

Quote from: Mohawk20 on April 11, 2009, 08:58:22 AM
The warmer air might reflect the red colour from higher up in the sky, so at dusk the sky has more red in it, while dawn has more cold colours like yellowish reds. And some hazy whiteness as TU suggested.

No, it has little to do with reflection of red colour. It's really redshift, in both cases. I think with your refraction-index part and maybe some hazy whiteness the majority of the difference is explained.

sjefen · April 11, 2009, 11:09:10 AM

That's what I tried to say. Sun warming up the atmosphere.

- Terje