Planet/Atmosphere shader help?

Hey all,

I'm planning to create a solar system animation in Unity 4.0. I've found the planet shader below to start with. The one on the wiki had an awesome atmosphere effect that I liked but it seems tied to the camera not lights in the scene.

http://entitycrisis.blogspot.com/2011/01/planet-shader-2.html

The issue I'm having is how to get that light bloom effect when the light source peeks from behind the planet. I thought I could perhaps fake this by duplicating this shader, adding a texture alpha channel to it, and applying this new shader to an outer shell of planetary geometry.

This is probably simple for anyone who knows ShaderLab but I know nothing of the code.

Can anyone help me with this? Also any general ideas to help create a good looking solar system are much appreciated! Thank you!

D

 

If you're going to skip on making an actual atmosphere with scattering, I would go for a combination of a rim shader and "wrap around diffuse" shader. There are examples of them here:
http://docs.unity3d.com/Documentation/Components/SL-SurfaceShaderExamples.html
and here:
http://docs.unity3d.com/Documentation/Components/SL-SurfaceShaderLightingExamples.html

You can just add the rim shader over it with a specific color (i.e. blue), then lower the gamma of that result (to make the back less lit), and multiply it by the diffuse texture.

You'd probably have to do some kind of scattering or at least transparency shader to get a "bloom" effect that is visible outside of the planet's edge.

 

I'll have to google this scattering. THis is intended for a live wallpaper on android devices so if scattering is too resource intensive I may have to find another method as you describe.

 

Were you meaning sub surface scattering? THought that was for surfaces that absorb light, like skin.

 

No, he said atmospheric scattering http://http.developer.nvidia.com/GPUGems2/gpugems2_chapter16.html

 

Thank you Rae

 

I'm attempting to use the scattering shaders from this thread:

http://forum.unity3d.com/threads/12296-Atmospheric-Scattering-help

None of the links in that thread are live still unfortunately.

I have the shaders applied to the correct nested layers but any light just illuminates the lowest layer diffuse model, and has no affect on the outer ones.

 

This is pretty much the be all/end all of atmospheres for Unity:

http://scrawkblog.com/2013/04/21/precomputed-atmospheric-scatter-in-unity/

 

Ooh...it would be awesome we can use this with Fog Color

 

Is this the effect your were after?



This is using the GPU gems atmospheric scattering. I have I working copy of this for Unity found here.

The precomputed atmospheric scattering project that duke linked to will not achieve the effect you are looking for as it only works from with in the atmosphere (although the original project that mines based on could do this)

 

Ty so much Scrawk

 

I'm looking to use this shader setup to make a solar system where I see the scattering as the planets move between the sun and the camera. Is this feasible with this?

It looks like this is dependent on the light being directional and in the center of the shaded object.

 

Well the scattering method can probably be reduced significantly in performance cost from what it could possibly be. I mean firstly you do not even need to use a sum/integral to calculate the amount of light that should be scattered, which is probably the most performance intensive part if you use a high resolution. Honestly though, from a scattering shader I've been working on recently, it does not make that much of a difference in quality if you don't know what you're looking for. For a decrease in physical accuracy you could get rid of it completely and just compute the scattering very cheaply by using the distance to the back of the atmosphere from your position, and then instead of mathematically computing the colors, just make a gradient map texture and sample from different locations on it depending on the distance of the atmosphere and the angle to the sun. I.e. set the texture up so that the sample location from top to bottom is controlled by the density of the atmosphere, and left to right is angle to the sun. Texture might be something like this:
http://i.imgur.com/o2FOjKE.png

 

Yes, this should be possible although you may need to modify the shader a little. The shader needs the light direction but lets say you have a point light. You can just pass in its position then subtract the verts position from the light position and normalize the result and you then have the light direction.

 

This looks fantastic, although I can't open it. Looks like you made this in Unity4? Any chance of backward compatible version?

 

Sorry kpod I only have Unity 4 installed on my computer at the moment.

 

That's haze, seen from the planet surface. Not what he was talking about. I'm looking to make an atmosphere haze using simple opacity falloff as seen in this render....

 

http://tamer.co/articles/atmospheric-scattering

 

Awesome swark, very cool. Ive been tweaking the shader to try and see if I can change the color of the atmosphere. Admittedly I know very little about shaders but its been fun trying to work it out and Ive learnt a bit but still no color change only brightness change. Any tips? I know from research the calculations are based on wavelengths scattering through particles principles - water etc. Mars is what I'm after. Thx.

 

Dont worry, solved it kind of. Just messed around with parameters. Now its time to suss out how I add a normal map. Reading the docs for that one. Lend a hand if any can? thanks all.

 

Scrawk your shader is great. I love it, if I turn HDR on for camera I get problems in the form of a blue ring around the planet. Any ideas thanks, linear colour space - deffered? Linear seems to be brighter vs gamma but thats not major. Thanks, be great to get some feedback.