= Environment/reflection maps =

== Overview ==

Environment maps are special images that represent the view from a certain point in all directions. You can use Environment maps in several places in Houdini.

Reflection maps:
    Some materials, especially highly reflective ones such as chrome, often let you specify a _reflection map_. This map is used to control the reflections that appear on the surface of an object with the material. This is much faster, though less realistic, than actually raytracing accurate reflections.
    
Image based illumination:
    [Area lights and Environment lights|/shelf/lightsandcameras] have a parameter that lets you use an environment map to control the light color emitted. Using an environment map to do this kind of image-based illumination creates the illusion that light from the surrounding environment is bouncing onto the objects in the scene.
    
    See also [image based illumination and ambient occlusion|/light/ambientocclusion#ibi].

Writing shaders:
    Many VEX functions and VOPs can take an optional environment map argument to give the color for a ray that doesn't hit any geometry.

== Creating an environment map ==

Use the [isixpack|/ref/utils/isixpack] utility to convert images into the special environment map format used by Houdini.

== Sample HDR images ==

Houdini includes three sample HDRIs (high dynamic range images) (in `$HFS/houdini/pic`) courtesy of [Dosch Design|http://www.doschdesign.com/products/hdri/]. These are low-res samples of HDRIs you can purchase from the Dosch website.

[Image:/images/light/DOSCH_CARB_04SN.jpg]

[Image:/images/light/DOSCH_DH207SX.jpg]

[Image:/images/light/DOSCH_SKIESV2_01SN.jpg]