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Thread: Transparent edges - planets atmosphere problem.

  1. #31
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    Quote Originally Posted by RebelHill View Post
    Except it DOES have incidence in the way it renders, as my initial image clearly shows. Its a consequence of the way volume rendering works. The way that you're thinking of it, like incidence to a surface would have no meaning, because there is no surface.
    So just to be clear, when you say there is no surface, you are referring to the volume in Lightwave?

    If so, I understand what you are saying.

    I'm just thinking of it in the context of calculating the incidence of solar radiation striking the top of the atmosphere and the reflection or refraction of that radiation.

    To get that, I would need the Lightwave volume to have surface qualities similar to our atmosphere; at least to the extent that it allows for incidence, reflection, and refraction.

  2. #32
    Goes bump in the night RebelHill's Avatar
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    No... I mean it's a mist, there is no definitive surface boundary such as the surface of a sphere. Or rather, the volume is composed of millions of tiny little surfaces (blobs/motes/particles/whatever). If you could apply a incidence based shade (and zoom in real close) you'd have this image, not the one you imagine you should get. Not to mention the fact that the atmosphere has no meaningfully visible levels of reflection or refraction (certainly not in the optical wavelengths), its almost ALL scattering and absorption.

    You're still stuck in the mindset of the ways that we used to need to fake such effects by using definite surfaces and trying to make them appear voluminous. There is no longer any need to do that, volume primitives behave now as real volumes do, which DOES include, incidence shading/scattering effects... again, look at the first "black planet" image I posted, dark in the middle, gets gradually lighter towards the edges.
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  3. #33
    Goes bump in the night RebelHill's Avatar
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    Also, you previously mentioned the uniformity of the volume, and that's certainly true when you have it alone... but a good study of why thats so would be to look at pics of the ol gas giants, which are basically just big fat volumetric spheres with no actual "surface". They're pretty uniform. You'll notice that you can just take a volume sphere by itself, pop on a procedural, and bingo, pretty convincing neptune.
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  4. #34
    RETROGRADER prometheus's Avatar
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    Quote Originally Posted by RebelHill View Post
    Also, you previously mentioned the uniformity of the volume, and that's certainly true when you have it alone... but a good study of why thats so would be to look at pics of the ol gas giants, which are basically just big fat volumetric spheres with no actual "surface". They're pretty uniform. You'll notice that you can just take a volume sphere by itself, pop on a procedural, and bingo, pretty convincing neptune.
    Yep,
    Can you describe gasplanets as "having atmosphere" or consisting of "atmosphere only" ?

    Ogo taiki did nice planet atmosphere realisticly, though it is a dead end for lw versions above 2015, and for those version it could work on...maybe to slow to render, otherwise it was nice.

  5. #35
    Goes bump in the night RebelHill's Avatar
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    Well, most are expected to have kind of solid core arent they, even if its tiny in comparison to the overall dimensions.

    Anyhow... with a bit of play Im finding its possible to get some really nice subtle effects... soft edges, gentle terminators, lovely shine through at the limb. Very quick and easy. Only thing not shown is the texture, which is nothing more than a procedural plugged into the scattering colour, thats it.
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  6. #36
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    Quote Originally Posted by RebelHill View Post
    No... I mean it's a mist, there is no definitive surface boundary such as the surface of a sphere. Or rather, the volume is composed of millions of tiny little surfaces (blobs/motes/particles/whatever). If you could apply a incidence based shade (and zoom in real close) you'd have this image, not the one you imagine you should get. Not to mention the fact that the atmosphere has no meaningfully visible levels of reflection or refraction (certainly not in the optical wavelengths), its almost ALL scattering and absorption.
    I'm pretty sure I'm not communicating efficiently.

    Incidence and the angle of incidence is a real thing; i.e., we use it to calculate the amount of em radiation (both visible and non-visible wavelengths) that strike the earth and the earth's atmosphere.

    Our atmosphere does have a large amount of scattering and absorption; but it also has reflection and refraction. We actually have manuals to address atmospheric reflection and refraction distortion in aerial and satellite imagery. It most certainly is in the visible range, although you may not actually be fully aware of it without being shown exactly where it is. When you see it, you definitely recognize it; and once you recognize it, you can't "un-see" it. Unfortunately, I work with a lot of people who can't un-see it.

    Also, we actually do measurements of incidence from the top of our atmosphere.

    Our atmosphere, like the volume in Lightwave we are discussing, is composed of an enormous number of particles. At the macro level where we observe our atmosphere, it acts like a surface for the purposes of measuring incidence.


    Quote Originally Posted by RebelHill View Post
    You're still stuck in the mindset of the ways that we used to need to fake such effects by using definite surfaces and trying to make them appear voluminous. There is no longer any need to do that, volume primitives behave now as real volumes do, which DOES include, incidence shading/scattering effects... again, look at the first "black planet" image I posted, dark in the middle, gets gradually lighter towards the edges.
    No no. I want to create a realistic simulation. I spend a considerable amount of my days creating imagery simulations; and the fact that the volumetric primitive lacks reflection / refraction or the ability to calculate incidence makes it a little less than ideal.

    From space, at a 90 degree angle of incidence, the areas of the atmosphere receiving the most solar radiation appear to be more translucent; as you move to the edges of the earth and the amount of solar radiation falls off, the atmosphere appears to become more dense. This effect can be greater or lesser depending on the concentration of the atmosphere in a given area, but it's there.

    I mentioned uniformity because in full illumination, if the volume were accurate, a portion of our volumetric sphere over our "earth" that receives the greatest direct illumination would be appear to be more translucent; it would become more dense as you moved to the edges.

    We can approximate that effect in other ways; but the calculation of the incidence of a sphere actually provides this all by its lonesome.

    Gas giants are fully dense, i.e., the density of their atmospheric volume is such that incidence doesn't have the same clear visible effect. In some ways that makes them tend to appear flat, although in some of the newer imagery of neptune from the European Southern Observatory's VLT, (from your example), incidence becomes clearer.

    Anyhoo, it's all good. It's something to consider and work on for me.

  7. #37
    Goes bump in the night RebelHill's Avatar
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    I didnt say that there was no reflection nor refraction, simply that it was minimally visible. Sure, when you're taking (precision) images of the ground from orbit, these effects become meaningful, but when you're just doing "pretty photos" of the earth as if from space, the effect is gonna be negligible at anything other than high magnification or massive resolution.

    As for the incidence based effects... let me point you AGAIN to the first black planet image I posted... darker (thinner atmosphere) on the front face area, progressing to lighter (denser appearance) towards the limb. It's right there... If you're not getting it, work on your volumetric settings, because it DOES work.

    If you're determined to add this reflection/refraction stuff into the bargain... then I'd suggest augmenting the setup by using both a volume object and a "shell" surface, let the volumetric handle the absorption and scattering, haze and "rim light", and the mesh the reflect/refract. Alternatively, you can try out the Sigma 2 material, which is a full volumetric material providing for the full gamut of surfacing effects... reflection, refraction (internal and surface), absorption, scattering... the lot.
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  8. #38
    RETROGRADER prometheus's Avatar
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    Crying..crying....
    http://www.asahi-net.or.jp/~pq1a-ogs/taiki_e.html

    Ogo had refraction, it had too many settings, you could create almost any kind of atmosphere, but hard to know what you were doing, slow to render and difficult to control quality settings all over the place.
    But if used right..I think it could produce the best results out there...only matched by Terragen, ozone could not create planetary views like this.

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