Snow Top ***UPDATE NO. 3**

rcallicotte · November 06, 2007, 01:16:47 PM

Better, Hannes. Something about the human eye having a pupil makes photography and TG2 more interesting.

bigben · November 06, 2007, 07:11:40 PM

Wouldn't it be simpler to use GI settings to do this? Rather than the snow emitting light (risking overexposure in brightly sunlit areas, and decreasing the shape detail in shadows) that is coloured to remove the colour cast, you can change the enviro light's colour/strength on surfaces. An alternative would be to give the snow some reflectivity (makes a bit more sense) and possibly a slight blue colour to compensate for the light.... although personally I think the whole scene looks better if you try and fix it with lighting tweaks.

Matt · November 06, 2007, 07:32:28 PM

Quote from: calico on November 06, 2007, 09:58:34 AM
I almost like the one on the left better. It has something to do with how the eye registers it in real life...

The one on the left is more physically plausible. The luminosity in the image on the right would not happen in nature - there isn't enough light coming from the scene to illuminate it that brightly. Snow is not luminous; from a distance the only thing that contributes to its brightness is the amount of light falling on it and the amount of light it is able to reflect.

Matt

Matt · November 06, 2007, 07:39:58 PM

My preference would be to increase camera exposure until you like the brightness of the snow. Changing sunlight intensity has the same effect, because more sunlight entering the scene also results in more environmental light (global illumination) scattered onto the shadowed parts of the scene, affecting everything. To make the shadowed snow bluer, either make the sky bluer or make the sunlight bluer, depending on how much you want to affect various parts of the scene.

Only if these "photorealistic" tricks fail to get me to what I'm aiming for would I then try to tweak the enviro light from its defaults or add extra brightness to the snow.

Matt

Cyber-Angel · November 06, 2007, 08:37:44 PM

I have a question would it be possible (In future) for TG2 to support Albedo http://en.wikipedia.org/wiki/Albedo in its surfacing and take this into consideration at render time it might help with realism issues? It would be nice if at some point in the future if Terragen could have multiple non-arbitrary forward and backward light scattering which would make surfaces such as snow and ice (Not just these) more realistic but the implementation of Triple S will go part of the way in the interim period.

Regards to you.

Cyber-Angel

Matt · November 07, 2007, 04:13:34 AM

You can already control the albedo. When you give a surface a colour of white (1, 1, 1) you are saying it has 100% albedo. This works for any of the shaders in TG that use a Lambertian reflectance model for their diffuse component, and that's most of them (e.g. Surface Layer, Image Map Shader, Power Fractal Shader, Default Shader...).

Global Illumination in TG2 is calibrated to treat those values as albedo values and reflect light accordingly.

As for "multiple non-arbitrary forward and backward light scattering"... well, you wouldn't notice much difference in a render like this. From close up, yes, the appearance of snow depends on sub-surface scattering. The way light is scattered in snow often reminds me of cumulus clouds in miniature, and clouds certainly cannot be rendered realistically without some understanding of how light scatters inside them. But what specifically do you mean by "non-arbitrary" in this context?

Matt

efflux · November 07, 2007, 08:14:08 AM

I think the main problem boils down to the fact that light scatters into the snow so you don't see so much surface detail with shadows. In TG renders the snow looks OK in the shadows but once you can see a clearly defined detailed snow surface in sunlight then the realism breaks down. Maybe a way would be to make the snow very smooth. I've never tried snow so I'm just guessing.

dhavalmistry · November 07, 2007, 01:50:31 PM

a small update

a small cropped render of the bottom part....

I think the snow looks much better than previous version...

added snow on trees with variation...

10 hrs of rendering at 0.7 detail...

can anybody find a tree(s) half buried in snow??....

suggestions welcome...

nvseal · November 07, 2007, 01:54:10 PM

Looks good. The trees seem to need somemore variation in scale (at least from this crop).

dhavalmistry · November 07, 2007, 02:40:34 PM

Quote from: nvseal on November 07, 2007, 01:54:10 PM
Looks good. The trees seem to need somemore variation in scale (at least from this crop).

yes I will try that when I do the final version...

Cyber-Angel · November 07, 2007, 05:48:27 PM

Hi Matt,

By Non-Arbitrary I mean that in physical terms in nature that light dose not follow the same path in its exist point from the point of entry but follows multiple exit paths in the forward and backward directions in an Non-Arbitrary way. This can be seen in clouds (Multiple light scattering between water droplets in both forward and backward directions) and in snow where the scattering is between ice-crystals. In both cases the scattering contributes to the distinct look of both phenomana, sorry I am no able to explain it better.

Regards to you.

Cyber-Angel

bigben · November 07, 2007, 09:35:48 PM

This snow is looking better.

I've been going to try using a surface shader with a small displacement and favour depressions to use as (or combine with) a population density mask to see if it can produce a nice lowering of the population density along the ridges. I used to do this with a flow map from WM, but it would be really cool to be able to do this without an image map.

Quote from: Cyber-Angel on November 07, 2007, 05:48:27 PM
Hi Matt,

By Non-Arbitrary I mean that in physical terms in nature that light dose not follow the same path in its exist point from the point of entry but follows multiple exit paths in the forward and backward directions in an Non-Arbitrary way. This can be seen in clouds (Multiple light scattering between water droplets in both forward and backward directions) and in snow where the scattering is between ice-crystals. In both cases the scattering contributes to the distinct look of both phenomana, sorry I am no able to explain it better.

Regards to you.

Cyber-Angel

I think it should be arbitrary

For up close snow I add small (0.01 - 0.02) fake stones plus lambert shader plus GI. Looks crunchy up close and creamy at longer distances. You can also try mixing fake stone layers of slightly different colours (blue or blue/green) with their densities varying slightly by different slope restrictions.

dhavalmistry · November 08, 2007, 02:44:52 AM

another update.....

it took little longer than I though it would....12.5 hrs

had to do little touch up in photoshop due to GI bug in cropped renders...

I personally think I blew it....

anyway.....rest of the render should be done within couple of hours...

Kevin F · November 08, 2007, 11:55:10 AM

This is looking really nice. How did you put snow on the trees? are they just white(r) leaves or is some other method involved. Didn't Oshyan mention way back in January that he was working on a project to put snow on trees?
Did this ever get anywhere?
Kevin.

dhavalmistry · November 08, 2007, 12:22:50 PM

I dont know how far did Oshyan got but the snow on trees is dont in TG2 (of course I had to cheat)