Corona EXR format (CXR)

Images rendered in Corona Renderer can be saved into EXR files with additional metadata. This format is being referred as Corona EXR format (CXR). Files in this format can be later used to resume rendering, or they can be opened in Corona Image Editor. They are valid EXR files, but since they use some of the more advanced features, it may not be possible to correctly load them in some third party applications.

CXR files store just raw pixel data. They are not saved with applied color mapping, bloom & glare, etc. Instead of that all parameters required for these are saved in the metadata.


Files in the CXR format store additional render elements (channels) and attributes. Both are realized by standard EXR means.

Render elements (channels)

Name Description
CORONA_FB_WEIGHTS Single channel storing weight of each pixel, roughly corresponding to the number of taken samples. It can be used to optimally merge several CXR files rendered with different random seeds to produce a single CXR file having lower amount of noise.
VisibleDiffuse Hidden element for Corona Denoising.
VisibleNormals Hidden element for the denoising.
Hybrid Hidden element for the denoising.
HairIds Hidden element for the denoising.
OptixNormals Hidden element for the denoising.
Prefixed by Sqr Hidden elements for the denoising.
Prefixed by Denoised In case the CXR file has been already denoised, denoised variants of all denoised render elements are stored with this prefix.


Names of all additional attributes always starts with corona prefix.

Name Description
corona.iscoronaexr Equals to 1 when the file is saved in the CXR format.
Prefixed by Parameters for tone mapping, LightMix and used LUT.
Prefixed by Parameters for bloom and glare.
Prefixed by corona.curves Store used curve parameters.
Prefixed by corona.denoise Parameters for Corona Denoising.
Prefixed by Sharpening parameters.
Prefixed by corona.blur Blurring parameters.
Prefixed by corona.vignette Parameters required to apply vignetting.
Prefixed by corona.renderstamp Store text of file-save-time render stamp and other related settings.
corona.elements Ordered list of render element definitions. Each element definition consists of the element's name, type, and list of flags further describing the element's features and how the element should be interpreted with regard to tone mapping, bloom and glare, etc.
corona.stats.passes Total number of computed passes.
corona.stats.time Total time measured in milliseconds elapsed since render start.
corona.stats.raysPerSecond Average number of rays computed per second measured since render start.
corona.stats.raysPerSample Number of rays needed to compute one taken sample.

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