MAY 8, 2004
Tutorial: Realistic Earth
Create a realistic earth with C4D v8.0 and under with SLA.
v8.0+ and the Advanced Render module is required for the glow effect.
Clicking any of the tutorial images links opens the image in a new window. Move through the tutorial images in that window while reading the main text.
Getting started
For creating images of earth or other planets, you will need planetary maps that can be found at various sites on the net, kindly made available by NASA and others. For this tutorial you will need:
- an earth color map
- a bump map to match the color map
- a cloud map
- a specular map
At the end of this tutorial you will find links to good map sites where you can find what you need.
Creating the earth
Start by creating a sphere. Name it Surface and apply a new material with the same name and set the projection of the material to spherical. In the COLOR channel, load the surface map for earth and leave all the other settings at default.
Next, enter the DIFFUSION channel and load the same map but set the Mix slider to 50% to diffuse the color map slightly. Now enter the LUMINANCE and load the bhodiNUT Fresnel shader.
Figure 1. [Click to enlarge]
Create a narrow gradient from dark blue (inner) to white (outer) as seen in figure 1. You do not have to change the remaining settings but make sure you are using Cubic Knot interpolation, which should be default. This is done to complement the atmospheric glow of the earth which we will later complete using the atmosphere layer.
Now, exit the Fresnel window and set the Mix slider to 50% and enter the BUMP channel. Load the bump map (or the color map in case you have no separate bump map) and enter a high strength value. Set the sampling method to Square to really bring out the bumps. You can also add more bumps to this map by using the bhodiNUT Fusion shader and morphing the bump map with some 3d noise set at a very small global scale, but a good bump map is usually enough.
Next is the SPECULAR channel, which with the right lighting can produce a very good sunlight reflection on the water, as usually seen from space. This takes much experimentation to get right and will not be covered in detail in this tutorial. Our only suggestion is to experiment with the width and height settings as this very much depends on your light source and the angle of your camera. However, the most important part of this is to use a specular earth map to limit the reflection of light to the water areas of the earth’s surface, as land obviously does not reflect light in the same way.
Figure 2. [Click to enlarge]
The specular map is a black and white representation of the earth map with land being black and the water being white (figure 2). You can also set the specularity color to mimic the tones of the sun for added realism. Now the surface of earth is complete.
Adding the clouds
Figure 3. [Click to enlarge]
It’s always raining somewhere, and thus we need clouds. First, create a new sphere or duplicate the earth sphere, and increase its size so that it very slightly surpasses the size of the earth sphere. Name the sphere Clouds and apply a new material with the same name. In the COLOR channel, load the cloud map and leave all other settings at default. Create a negative image of the cloud map in any 2d application and load it in the TRANSPARENCY channel (figure 3), making it work as a transparency map, using default settings. Alternatively, you can make a negative image using the bhodiNUT Brightness/Contrast shader by loading your map in it and setting the low clip to 100% and the high clip to 0%.
Next, load the cloud map into the BUMP channel and use 100% strength with square sampling method to get the highest bump effect which will enhance the clouds, making them look more convincing. Next, enter the LUMINANCE channel and set the strength slider to 70% to illuminate the clouds, making them white and luminous.
Creating the atmosphere
Figure 4. [Click to enlarge]
To create the blue atmosphere layer of earth you create yet another sphere, making it slightly larger that the cloud sphere and naming it Atmosphere. Apply a new material with the same name. Enter the COLOR channel and select a marine blue color (R=117, G=160, B=55, and brightness at 50%). In the LUMINANCE channel, load the bhodiNUT Fresnel shader. Create a blue gradient that becomes slightly lighter outwards and leave the other settings at default as seen in figure 4. A 50% Mix is used here too.
Figure 5. [Click to enlarge]
Now, enter the TRANSPARENCY channel and load the bhodiNUT Fresnel shader. Create a narrow gradient with black (outer) and white (inner), but not as narrow as the one used for the surface material (see figure 5). Make sure Cubic Knot is used and all other setting set at default. Choose a clear blue color for the transparency (R=0, G=81, B=255, and 100% strength) and set the Mix slider to 95%. This will add slightly more color to the atmosphere and decreasing the Mix will add even more color.
Finally, enter the GLOW channel and use a low inner strength setting at around 3%, and an outer strength setting of 400%. The glow radius setting depends on the size of your sphere and should be about 1-5% of your sphere’s diameter. Finally, make sure that the Use Material Color box is marked. Glow is a post effect and will only be shown after the scene is rendered as it is a post effect.
Darkening the globe
Figure 6. [Click to enlarge]
To complete the earth, we need to darken half of the globe to simulate the phase of the earth. This effect should be very soft. As the earth reflects and captures light rays in its atmosphere, the non-exposed side is never entirely dark. This is done by creating an additional sphere that will cover the earth surface, the clouds and the atmosphere. Create and apply a new material named Shadow and load a bhodiNUT Falloff shader in the TRANSPARENCY channel. Open the falloff editor and create a black to white gradient. Increase its contrast by clipping the values (figure 6). Assign the material to the sphere with a spherical projection. Now use the texture tool (or insert texture coordinates) to rotate the texture at the right angle, coordinated with your light source.
Figure 7. [Click to enlarge]
In addition to the shadow sphere, enter the DIFFUSION channel of the Atmosphere material and load the bhodiNUT Gradient shader. Set the projection to 2D–U using a black to white gradient with default settings (figure 7). This gradient has to match the shadow sphere’s gradient in order to work properly as they combine so it might require some positioning and tweeking.
Last, add the same gradient into the Atmosphere materials DIFFUSION channel, to dampen the glow as well, as the shadow sphere won’t be sufficient. At this stage we have many transparent materials on top of one another. This will require a strong ray depth. Go in the Render setting, and increase the ray depth to 10.
Rendering the world
Figure 8. [Click to enlarge]
Adding a suitable background and using a light source placed in accordance with the darkening of the globe completes the scene. In addition to using the glow effect in the render settings, a SHARPEN filter (part of the Advanced Render module) with a low setting can also help to bring out details on the final render, embossing the clouds and the earth surface (figure 8).
Figure 9. [Click to enlarge]
The created earth can also be used for close-up scenes, as in figure 9. In this picture, a very high-resolution cloud map was used with the same settings described in this tutorial, with only the position and angle of the camera changed.
Links to planetary map and space imagery sites
NASA: the Blue Marble Image
Space-Graphics.com
Hubble Telescope
Planetary Textures
Peter Clevestig is featured in our Artist’s Gallery. His website is at www.dez3d.com
