Ambient Cubemaps

Cubemap texture applied to scene lighting for high quality lighting environments.

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The Ambient Cubemap lights the scene from a provided image. The image is mapped to a sphere in the far distance (implemented as a cubemap texture with the mip maps storing preblurred versions of the image). The blurry versions are computed in a way that they can be used for specular lighting with varying glossiness (sharp vs. blurry reflections) and they can be used for diffuse lighting as well. This effect is independent of the position a material is lit from. Viewer position, material roughness (for specular effects), and the material surface normal are all taken into account.

The Ambient Cubemap has very limited local shadowing (SSAO only). Use a Sky Light instead when representing the sky's lighting.

The Ambient Cubemap is only intended to be used for a subtle directional ambient term (useful in games with completely dynamic lighting), or for model viewer applications. Because light comes from many directions, we cannot simply use shadow maps for this light type. SSAO is applied to get contact shadows from nearby geometry (see Ambient Occlusion ). You can toggle the rendering of Ambient Cubemaps in the Level Viewport by selecting Show > Lighting Features > Ambient Cubemaps.

Ambient Cubemap


In this image, a cubemap image has been automatically laid out into a longlat format.



Cubemap Texture

The cubemap used for ambient lighting. The texture should be created by importing a .hdr image in the longitude/latitude sphere unwrapping format. The engine automatically precomputes blurry versions of the texture and stores the result in one cubemap texture. The lower resolution mips of the texture store the diffuse preconvolved version of the HDR environment.


A scaling factor for the brightess of the effect. Possible uses: brightness tweak existing cubemaps.


A filter color to apply to the cubemaps. Possible uses: colorize existing cubemaps, animate a sky color change.

The cubemap in this image is derived from a light probe by Paul Debevec.

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