Environment Maps Explained
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The simplest way to light a three-dimensional surface is to illuminate it by a point light, which simulates light coming from a single point in space. The left half of the following illustration shows a height map which defines a 3D surface, and the right half of the illustration shows that surface illuminated by a point light.
Although point lights are effective in creating the impression of a three-dimensional surface, the resulting images are often not particularly attractive or realistic. This is because in nature objects are not lit by point lights, but instead receive varying amounts of light from all directions. Environment maps (also known as HDRI spherical panoramas) help solve this problem by encoding the illumination coming from all directions in a given environment within a single image. This image can be thought of as a sphere that has been cut open and flattened onto a two-dimensional surface.
There are a variety of map types that can be used to store an environment, each corresponding to a different way that a sphere can be flattened. Three of these map types are shown below. Clockwise from the top left, the illustration shows the same environment in latitude/longitude format, mirrored ball format, and horizontal cross or cubic format.
The following illustration shows the height map from the beginning of this page. But instead of lighting the surface with a point light, four different environment maps were used. As you can see, simply changing the environment map can create a great variety of surface effects that are realistic and stunning.
Environment maps can be used within Genetica for realistic lighting and reflections. There are a few ways to do this.
•For users of the Pro and Studio editions of Genetica, the environment nodes can be used to create sophisticated node trees that use environment maps in various ways.
Environment maps aren't only for use within Genetica. With the Render Environment Map dialog, available in the Pro and Studio editions of Genetica, you export environment maps created within Genetica for use in other applications such as 3D graphics programs.
Environment maps are also useful in games, where they can be used to create convincing real-time effects. The following illustration shows how modifying an environment map within the Edit Environment Map dialog can significantly change the influence it has on a model's surface.
Environment maps are also referred to as HDRI spherical panoramas. This section explains what that means.
A panorama is a wide view of a scene. For example, the following mountaintop panorama was created by stitching together several photographs. This type of panorama is typically called a "cylindrical" panorama because it can be visualized as a cylindrical slice of the scene where the ends (top and bottom) of the cylinder are missing. In other words, this panorama allows us to see in all directions from the location of the photographer except for the sky and ground that were directly above and below her. Environment maps are referred to as "spherical" panoramas because they contain light data originating from all directions, and can therefore be visualized as comprising the points on a sphere.
"HDRI" stands for High Dynamic Range Image and this refers to the fact that environment maps in Genetica contain light information that extends beyond the standard 0 to 255 color range that is inherent in most bitmap images. This means that the environment contains detail in both the brightest and darkest parts of the image, allowing the environment map to be used for the most realistic lighting and reflections.
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