Hello DELTAGEN Lovers,

With the DELTAGEN 22x Release we have introduced a new material named Mesh light, only working in GPU Global Illumination. It allow to study screen luminance with angle-dependencies by using an IES file for light profile and distribution.

How this work in GPU Global Illumination

This new material applied to a mesh/geometry allow to display some luminance properties with intensity and direction informations. This is possible by combining an Emission value (lumen/candela/lux/nits), Emission texture and an IES profile.

Luminance / Illuminance Analysis

In Global Illumination mode, you can set your camera in Luminance or Illuminance pass.

You can check how much light is emitted in your scene (Luminance)

You can check how much light is bouncing into your scene's geometries (Illuminance).

Set Mesh Light Material

In the mesh light material, after having set to profile type, loaded the IES file, and set to 1 candela, we have to take care of the IES orientation.

Correct IES File Orientation

If your IES profile don't have the correct orientation, here are the step to get it in the direction / orientation.

• For this we have first to orientate the screen geometry, that we have placed into a group.

• Then we orientate the group to match the IES direction. In my case the IES is pointing toward Z negative, to the floor. So I select the group for rotation, I pick “use object center”, and in Y axe I set 90 degrees. Now my screen is looking toward the floor, and its new Z direction is matching the Z direction of the IES file.

• We have to reset now the new orientation of the screen, so I use Flatten transform feature on the group with Alt+F, and I select Yes.

• All Transform Center and Rotation are now resetted.

• We have now to get the screen to the initial orientation. During the rotation, the IES embedded in the Mesh light material will be rotated too. Use again Transform center and set Y = -90

• Now you get the IES working in the correct direction and you have angle dependency luminance from the screen in Global Illumination. DON’T Flatten Transform this group or the IES file will come back to its initial position.

You are all set to perform great studies!