Ward-Studios.com 3D Earth Project
Creating the world in 7 days (or less!)
When I was working on 3D scenes in space I wanted to have a realistic looking Earth in the background for some scenes. I tried some basic built in planet objects, then a basic sphere with a texture map, but none of those were working for me. I started to design my own 3D Earth model for use in my other projects, however this task quickly took on a life of its own and became the project. My thirst for an ever more detailed and realistic looking 3D model of the Earth grew. I began scouring the internet looking for a highly detailed terrain map that I could apply to a large sphere to create a realistic globe.
How did you start creating your own world?
Some of the first terrain maps I found were pretty low resolution. While they made for a nice looking globe that didn't take up very much memory for background rendering, they made for pixelated low resolution close up renders. If the globe took up more than about one quarter of the render area at 720 HD, the image started to show blurring. The water was also pretty dissapointing and the lack of clouds was strangely noticeable. The terrain map I finally settled on is a massive 21600x10800 (233 Megapixel) terrain map compiled by NASA's Earth Observatory (The Blue Marble Project). This huge image applied as a texture is a huge strain on my rendering software and computer memory. Technical crap for the curious: The model file, as saved with textures, is 188MB. It takes about 2GB of system memory to load the model. It loads fine (but slowly) on my Windows 7 box with 4GB of memory, but my Windows XP box with 3GB of memory is unable to open it.
What did you do about the water and clouds?
With the massive terrain map selected, the next task was to find a nice alpha layer map to use to mask the land area, leaving the water areas transparent. A three dimensional water sphere placed just slightly inside of the terrain map sphere becomes visible in all the places where there is no land. This water sphere gives me greater control over features such as the color of the water, wave height, and other features. This smaller 16200x8100 (131 Megapixel) image doesn't provide for the increadible resolutions like the terrain map, so some coast lines look a little fuzzy on renders where less than an area the size of half of the United States fills the entire screen.
And the clouds?
Next I needed some clouds to add a little flavor to the model and make it more realistic. A cloud free globe is impossible. The cloud map I selected has very few clouds and is pretty unrealistic, but it is done in such a way that it doesn't block most of the world's land masses. This 8092x4096 (33.6 Megapixel) image is the lowest resolution of all the textures that I used on my model, but because of the way I am rendering the clouds this isn't a huge drawback. The clouds are white where they are thickest and fade to black where there are none. To incorporate this onto my model I used the clouds layer as the color map and then simply used the inverse of the image (making the thickest clouds black and fading out to white where there are no clouds) as the alpha mask. This makes the thickest clouds solid and white while thinner clouds become lighter grey and partially transparent. Of course where there are no clouds it is completely clear.
What about the atmosphere?
There were still 2 aspects missing from my globe to make it more realistic. The more obvious was the atmosphere. I added a faux atmosphere by encasing all of the texture and water spheres inside a special transparent sphere with certain color and fade out properties that mimic an atmosphere effect, especially towards the visible edges of the rendered globe. The other effect I was missing was lights at night. Our world's dense population centers emit huge quantities of light pollution which is clearly visible on the dark side of the planet from space. To accomplish this I created another texture sphere just slightly above the terrain sphere and applied a 2400x1200 (2.9 Megapixel) texture of the lights at night map compiled by NASA's Earth Observatory. Like the cloud layer I used the inverse of this image to create the transparency alpha layer for it. Then to give it the glow to be seen at night I made this new layer slightly luminous. The spots are slightly visible on sun lit portions of the globe model, but they gleam across the dark parts of the globe creating amazing night effects.
What are the limits of your model?
Two limitations I have with the model at this time are as follows. I can't have a partial phase of the earth (ei: One side of the visible globe dark and the other side light) with the atmosphere visible. When I do this, the atmosphere creates an unrealistic glow around the dark portion of the visible disc of the Earth. The other limitation is similar, If I leave the lights at night mask enabled it leaves splotches on the sunlit portion of the Earth's disc. When I do render a phased Earth for the time being I leave the lights at night mask on and turn off the atmosphere for the best effect. I will continue to attempt to make the model even more realistic in the future.
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