# Does normal mapping make sense for a view of earth from space?

I am working on a planet visualizer, which at this point is little more than the NASA blue marble image applied as a diffuse texture. For the atmospheric rim, I am simply blending in a constant color depending on Fresnel. It looks like this:

Besides the obvious problems (no clouds) I am struggling to understand what techniques are applicable at this scale. As I understand it, normal mapping is simply a modeling of surface features below the threshold of polygon resolution. Likewise, roughness-based BRDFs are simply a modeling of surface features below the threshold of normal maps. In my case, I am using the 8k texture map at 500m resolution. Does it make sense to normal map the Earth from this distance? How would I even do that? Is there a height map for the planet?

Are there other techniques that are more applicable to rendering (real) planets like this? My next step is to make a specular mask based on water cover, but I feel like I am missing something else.

P.S. I noticed that the NASA blue marble image didn't render well when I enabled gamma correction, nor when I divided its texel values by $\pi$ before computing the light value. I'm not sure why that is.

• I've guessed that the capitalised "PI" was referring to the constant $\pi$ as I couldn't think of an acronym that would fit. If this is not your intention please edit to correct. – trichoplax Apr 4 '17 at 21:00

## 2 Answers

In my opinion, yes, it does. I've heard it claimed that in reality, the ratio of the tallest mountain on Earth to the Earth's diameter is smaller than the variations in height of an apple's skin to its diameter. So I can't say that it would be realistic, but it certainly looks better than not doing it. At the least it gives you some shading between high and low spots, even with a simple directional light.

• The effect will also be more noticeable at the terminator as it would add some variation to an otherwise perfectly smooth curve. – PaulHK Apr 5 '17 at 5:38
• Even if it is a shadowside slope of a mountain gets less light rhan one without. Even self shadowing by some method might be noticeable. – joojaa Apr 5 '17 at 14:18

I would say 'no' to the question about normal mapping, it probably isn't worth it. Geological "texture" from local surface orientation seems to have a very minor effect on the appearance of the earth from space. Getting the atmospheric scattering and variations in diffuse albedo (diffuse / specular maps) correct is probably 100x more important.

The analogy to the apple made by another user, while may be correct, is less relevant than it seems, since the apple's surface is very shiny and has no atmosphere.