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New Sky/Atmosphere model in 4.24

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  • replied
    I have a number of questions about the SunSky and the changes I have to make to use it. First, is there a technical guide on how to use it?

    Second, my particles systems now are black. I had a blood spray emitter upon hit that was red, Now it is black...

    thoughts?

    Originally posted by pf_breton View Post
    Hi,

    I need to give you some background on this prior to answer individual points below.

    The SunSky positionner is a plugin that was added in Unreal in 4.21. It lacked of proper shading technology (physical sky). In this release, this has been added to it in the form of extra components that can be used individually. The main use case is for Architecture where maintaining a notion of physically correct values for lighting, camera EVs and material parameters is a recommended practice.

    From the comments i read below it seems that you are starting from a project template that isn't right for that type of use case and hit all the roadblocks that are solved by the Architectural Visualization project templates. I'll get to that below.



    In project settings, enable the following options:

    Enable Extend default luminance range in Auto Exposure = true
    Apply Pre-Exposure before writing to scene color = true

    That will allow lights to go from low to very high ranges.



    The lower part of the sky hemisphere is usually done by an exponential height fog that should be added separately to the scene which isn't part of the Sun Positioner plugin.



    This is not the Hosek & Wilkie but still physical. Its using a derived version of the Bruneton sky which has several advantages over the Hosek & Wilkie. Its not something that was defined arbitrarily as you imply. The parameters are different (and more extensive) but it doesn't means is physically incorrect because of that.



    We have hidden the Sun Positionner plugin in Unreal by default but enabled it when using the project templates dedicated to Architectural Vis. However you don't need to use that plugin to use the new Sky shader. Just add a Sky Atmosphere actor from the Visual Effects category and you have it.

    Leave a comment:


  • replied
    I'm trying to get a skin shader working with the new light model, but I find that unless I disable skylight, the skin and eyes look "milky". Has anyone else eperienced this, and / or know what I should be doing to prevent it? shader: https://imgur.com/a/4KACT5d and this is the issue with skylight: https://imgur.com/a/zV54DRr

    Leave a comment:


  • replied
    Originally posted by Rareden View Post
    Tim Hobson
    Thanks for the info
    Additionally, is it possible to allow this component to work with world origin shifting, Currently the atmosphere gets shifted where ever you rebase the world origin.
    My HLSL knowledge is rudimentary so to my untrained eye this section of code in the shader seems to be responsible for the position of the atmo in the world
    Code:
    float3 GetCameraPlanetPos()
    { return GetCameraWorldPos()*CM_TO_SKY_UNIT + float3(0, 0, Atmosphere.BottomRadius);
    }
    It seems that its grabing the player cameras position and a fixed world 0 position rather than the components position or a predefined one thus causing it to move back to world 0 when ever you shift the origin.
    I was going to have a crack at changing it or if you have any better suggestions, anyone else know about HLSL and what is available for a actors position in a shader?
    I second this as well. Having the Sky Atmosphere renderer actually attached to the scene component gives it inherent positioning properties, such as being able to be properly positioned when rebasing the world origin. I may play with the code later and see if I can get it working.

    Leave a comment:


  • replied
    Originally posted by Warner V View Post

    Try switching on "Support Sky Atmosphere Affecting Height Fog" in the project settings
    I did. It allows me to have extremely complicated set of over 40 parameters to control the color below horizon in a way which makes it still almost impossible to set up a specific color. It's a model for approximation of a fog fading in a distance. It's not a model to specify solid shaded surface color. I go into great length describing why that is not a solution on the previous page.

    Leave a comment:


  • replied
    In my example Earth is at the Origin in 4.24 with the Sky Atmosphere. Moon in front of Earth and the atmosphere renders in front of the Moon.
    Wondering if I'm missing something.
    Attached Files
    Last edited by GTJC; 12-16-2019, 10:38 AM.

    Leave a comment:


  • replied
    Originally posted by sukovf View Post
    Hey. I'm facing the exactly same issue as Rawalanche and can't get rid of black color below the horizon. There's an exp. heigh fog actor in the Archviz example that fills up the below horizon area. Its color responds to the color of the sky and gets completely black during the 'night time'. That's cool.

    However I'am unable to mimic this behaviour in an empty project. Create an empty Map, place a Sun and Sky Actor (leave Height Fog Contribution set to default 1.0 for the SkyAtmosphere Component) and an Exponential Height Fog Actor into it and enable 'Support Sky Atmosphere Affecting Height Fog' in Project Settings. The fog retains its bluish inscattering color and totally ignores the sky color.

    I'm pretty sure I'm just missing something banal but can't figure out what that might be...

    Click image for larger version Name:	template.jpg Views:	0 Size:	165.3 KB ID:	1697467Click image for larger version Name:	my.jpg Views:	0 Size:	104.5 KB ID:	1697466
    Try switching on "Support Sky Atmosphere Affecting Height Fog" in the project settings

    Leave a comment:


  • replied
    Question:

    Is there a way to get some hold of the materials / BP's for the clouds (as demonstrated in <link> (and <link>)? In the 4.24 release I can find the "M_SkyTimeOfDay" material but it has a heave impact on performance so we're trying to get clouds that are performing decently..

    Leave a comment:


  • replied
    Originally posted by Haoris View Post
    Is there a way of changing the sun size? I tryied adding an atmopheric fog and reducing "sun disc scale" but it does absolutly nothing. It's a big problem when you use high bloom values as it makes the sun way too big.
    Haoris
    Its based on the "Source Angle" in the directional light.
    You can think of it as how close/big the sun is in the sky, the greater the number the larger the apparent area the light is coming from

    Leave a comment:


  • replied
    Is there a way of changing the sun size? I tryied adding an atmopheric fog and reducing "sun disc scale" but it does absolutly nothing. It's a big problem when you use high bloom values as it makes the sun way too big.

    Leave a comment:


  • replied
    Hey. I'm facing the exactly same issue as Rawalanche and can't get rid of black color below the horizon. There's an exp. heigh fog actor in the Archviz example that fills up the below horizon area. Its color responds to the color of the sky and gets completely black during the 'night time'. That's cool.

    However I'am unable to mimic this behaviour in an empty project. Create an empty Map, place a Sun and Sky Actor (leave Height Fog Contribution set to default 1.0 for the SkyAtmosphere Component) and an Exponential Height Fog Actor into it and enable 'Support Sky Atmosphere Affecting Height Fog' in Project Settings. The fog retains its bluish inscattering color and totally ignores the sky color.

    I'm pretty sure I'm just missing something banal but can't figure out what that might be...

    Click image for larger version  Name:	template.jpg Views:	0 Size:	165.3 KB ID:	1697467Click image for larger version  Name:	my.jpg Views:	0 Size:	104.5 KB ID:	1697466
    Last edited by sukovf; 12-12-2019, 06:15 AM.

    Leave a comment:


  • replied
    Originally posted by Rareden View Post
    Tim Hobson
    Thanks for the info
    Additionally, is it possible to allow this component to work with world origin shifting, Currently the atmosphere gets shifted where ever you rebase the world origin.
    My HLSL knowledge is rudimentary so to my untrained eye this section of code in the shader seems to be responsible for the position of the atmo in the world
    Code:
    float3 GetCameraPlanetPos()
    { return GetCameraWorldPos()*CM_TO_SKY_UNIT + float3(0, 0, Atmosphere.BottomRadius);
    }
    It seems that its grabing the player cameras position and a fixed world 0 position rather than the components position or a predefined one thus causing it to move back to world 0 when ever you shift the origin.
    I was going to have a crack at changing it or if you have any better suggestions, anyone else know about HLSL and what is available for a actors position in a shader?
    Yes this! I hope they will fix this. Would be amazing for space games!

    Leave a comment:


  • replied
    Tim Hobson
    Thanks for the info
    Additionally, is it possible to allow this component to work with world origin shifting, Currently the atmosphere gets shifted where ever you rebase the world origin.
    My HLSL knowledge is rudimentary so to my untrained eye this section of code in the shader seems to be responsible for the position of the atmo in the world
    Code:
    float3 GetCameraPlanetPos()
    { return GetCameraWorldPos()*CM_TO_SKY_UNIT + float3(0, 0, Atmosphere.BottomRadius);
    }
    It seems that its grabing the player cameras position and a fixed world 0 position rather than the components position or a predefined one thus causing it to move back to world 0 when ever you shift the origin.
    I was going to have a crack at changing it or if you have any better suggestions, anyone else know about HLSL and what is available for a actors position in a shader?
    Last edited by Rareden; 12-10-2019, 11:56 PM.

    Leave a comment:


  • replied
    Exactly what I worried was going to happen happened. The new atmosphere model made it all the way to the final 4.24 release without ability to specify below horizon color, despite several preview releases. I'd expect this kind of development from Autodesk, but definitely not Epic :/

    Leave a comment:


  • replied
    I would like to comment on this....

    First, thank you Tim Hobson and Sebastien Hillaire for greatly improving the environment options available on UE4. I've personal have been using linear workflows, HDRIs, and advanced exposure controls in architectural animations for about 15 years in 3ds Max and I completely understand the challenges. What you've done in 4.24 is a huge improvement and it appears to only be the beginning.

    Second, a lot of people are complaining about black bottoms under the horizon. Welcome to what happens when you have zero geometry in empty space. This is very common especially with professional HDRI scenes without geometry. I've personally create landscapes that expended out to 100 miles of real world accurate geometry. Or created infinity oceans. Although I haven't used the new features allowing you to view your site from space, as the new SunSky system appears to allow you to do, but I imagine the best solutions are having geometry at the edge of your scene to fill in the black area. But what they have done so far deserves a thanks, not criticism.

    Again, thanks Epic!!!

    Leave a comment:


  • replied
    Originally posted by Tim Hobson View Post
    - The black area below the horizon: that is not for the sky to simulate/render/fill up. You should put your world/landscape there, use SkyLight bottom color, or control it via skydome shader.
    This is an inadequate answer unfortunately. Placing geometry large enough to not cause any gap between it at the horizon line can result in level issues and precision errors. Such geometry would have to be way too giant to cover distance approximating infinity. Specifying color below the horizon using SkyLight bottom color is also inadequate for 2 reasons:
    1, This will completely override anything below the horizon, so if there is any kind of height fog atmosphere present, which is affected by scene lighting, such contribution will be missing from the SkyLight capture below the horizon.
    2, This change will only affect illumination from the SkyLight, not actual directly visible representation of the Sky atmosphere.

    Almost all the Sky atmosphere environment models in both realtime (Unity, Godot) and offline (Vray, Corona, Arnold) renderers have non-black representation of the color under the horizon. It's that way for a reason.

    Leave a comment:

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