Level – Advanced VRED/20150324samarth.gupta@autodesk.com

Replicating the photometric parameters in VRED

This paper describes how to replicate the photometric parameters supplied by the light OEMs to accurately visualize them inside VRED.

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Import the geometry provided by the supplier ( in this case :LY G6SP, Advanced Power TOPLED, yellow by OSRAM )

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Separate out the area from the geometry which actually emits light as shown next .

Right click on the geometry in scenegraph

Edit-> Geometry->

Split geometry into primitives

Right click on the surface to separate out

Edit-> Surface->

Create shell from selection

A separate shell representing the light surface gets created in the scenegraph

The luminous intensity value provided by the supplier is 13.4 lumens (luminous flux ), but the unit available within the incandescense tab of a plastic material for input is only in candela/sq m. So we need to convert the 13.4 lumen to a corresponding value in candela/sq m.

Create a Area light ( Disk light ) and visually adjust the size as the size of the light emitting geometry

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Enable the photometric parameters in the render settings and select ‘Adjust Values” as the light values are to be changed and NOT the scene behavior. Notice that immediately the units of light properties change in the box.

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Enter the values in “Lumen” in the Light properties Box. Now pull down the menu and select the unit as “ candela/sq m “; the corresponding value changes.Note this value in “ candela/sq m “ ( 965914.8 in this case )

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Hide the Disk Light, as it was only used as a helper object.Enter the values in “candela/sq m” in the incandescense tab of the plastic materialNow click on the color and select the “spectrum” tab in the boxLoad the file “…spectrum.txt “ provided with the supplier dataThis loads the realistic color spectrum for this light / material ( VRED supports supports OSRAM spectrum files and allows drawing individual curves )

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OSRAM data : Common Knowledge Repository/Light Simulation