BlendLuxCore LightPanel

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Props lampdata.png

Header

The available light types are:

  • Point
  • Sun
  • Spot
  • Hemi
  • Area

Point

See also: Blender manual.

Power/Efficacy

Radius: Defines the size of the point lamp. If greater than zero, the point lamp is a sphere, but only in shadow and reflection calculations. It can not be viewed directly, so it will always be invisible to direct camera rays. A higher radius leads to softer shadows.

IES File

Image: Projected spherically. If black/white, it can be used similarly to an IES file to drive the emitted light distribution. If the image is colored, the point light acts like a spherical projector.

Sun

Emits parallel light rays, so the position of the sun in the scene does not matter - only the rotation matters.

If you are using a sky lamp for your world, you should link the sun to the sky. This is a convenience mechanism and allows to set the gain, rotation and turbidity of both sun and sky simultaneously. You can link the sun either by pressing the "Attach to Sky" button in the sun settings or by going to the world panel and selecting it in the "Sun" dropdown field.

Sun type: "Sun" or "Distant".

  • Sun: Simulates a physical sun, as viewed through the earth's atmosphere.
  • Distant: Simulates a light source that is infinitely far a way, but does not simulate interaction with an atmosphere. Can be used to simulate a near star in space when rendering science-fiction scenes.

Relative Size: Size of the sun. Larger values lead to softer shadows.

Turbidity: "Foggyness" of the atmosphere. A low turbidity value simulates a day with very clear air, while a high turbidity value simulates a high amount of fog/particles/dust/smog in the air.

Spot

See also: Blender manual.

Power/Efficacy

Spot Size/Blend: See the Blender manual.

Image: If an image is selected, the spot light is turned into a projector. In this mode it will emit light in a rectangular pyramid frustum, not a round cone as without image.

Hemi

This is an alternative environment light which can be used instead of the HDRI light type in the world settings. The only difference is that it allows to rotate the HDRI around any axis, not only the z-axis.

Image: Usually you want to use a HDR image here (extension ".hdr" or ".exr"). Some places where you can get them are linked here. You can also use normal LDR (low-dynamic range) images (".jpg", ".png" etc.) but they will light your scene very uniformly and won't create strong shadows and highlights.

The image should use the latlong mapping (latitude-longitude). For an example see the image below. (It is the same mapping produced by LuxCoreRender's panoramic camera)

Gamma: Should be set to the gamma of the image. HDR images are usually saved with gamma 1.0, while most LDR images are usually saved with gamma 2.2.

Sample Upper Hemisphere Only: Enable this option if you are using a ground with shadow catcher material in the scene. This option will prevent shadows being cast from below, which would lead to incorrect shadow catcher appearance.

Hotel Lobby panorama luxcore.jpg

Area

See also: Blender manual.

Note that LuxCore has a more convenient feature than portals: the Visibility Map, which is enabled by default and does not require manual placing of portal lamps.

Power/Efficacy

Visible to Camera: The area light is actually a meshlight (two triangles forming a plane). This setting controls if the mesh is visible to the camera or not. It is just a shortcut for the same setting in the LuxCore Object Setting.

Spread Angle: How directional the light is emitted, set as the half-angle of the light source. Default is 90°. Smaller values mean that more light is emitted in the direction of the light and less to the sides. Note that very small spread angles can be problematic to sample and might lead to noise in the scene or no light being emitted at all if the light source is very small. If you need a very small spread angle, consider using a custom IES file instead. If you need parallel light rays, use the laser option of the area light instead (see below).

Shape/Size: See the Blender manual.

IES File

Laser: Turns this lamp into a laser that emits parallel light rays that start at its location (as opposed to the sun/distant lamps, which also emit parallel light rays but are always infinitely far away). The area lamp was chose to represent this LuxCore light because it can visualize the laser light radius. However the laser light source will emit light in a circle shape, not quadratic like the area lamp shows in the OpenGL viewport.

Power/Efficacy

(Only available when light type is point, spot or area)

Power: The lamp power in watts.

Efficacy: The luminous efficacy in lumens/watt.

IES File

IES files are text files that allow to control the shape of the emitted light of a lamp. They are supported by the point and area lamps and by the emission material node. You can find a few links to sites offering IES files for download on the External Resources page.

In BlendLuxCore, you can either link to an IES file in your filesystem somewhere, or you can copy the contents of the IES file into a text block inside Blender and select the text block as IES source in the lamp settings. The latter option has many advantages over simply linking to a file on disk.

For example, you could create a .blend file with many lights using IES files to use it as a library for your projects. If you use text blocks, they will be linked/appended along with the lamp when you link/append them into new projects. If you use the filepath option, the linked in lamps will probably no longer find their IES files.

Lighting IES example 2.jpg

Performance

Importance: How much processing power to spend on this light source compared to other light sources. Used to scale the light importance computed by the light strategy. For instance, if you set a uniform light strategy, a light with a user importance of 2.0 will be sampled 2 times more often than one with 1.0. If you use a power light strategy, the user importance will be multiplied by the light power.

When you manually set the importance, you usually also want to set the light strategy to uniform (so you have full control on how the lights are sampled).

Build Visibility Map: (only available if light type is Hemi) If enabled, the visibility map for the environment light source is computed at the start of a final render (not in viewport).

Visibility

(Only available when sun or hemi type is selected)

Here you can enable/disable the visibility of the world background to the three light bounce types. This setting is not supported by the Bidir engine as of v2.0alpha7.

  • Diffuse rays include for example the matte material, the matte base of the glossy material, the matte translucent material etc.
  • Glossy rays include any "non-sharp" specular reflections/transmissions with a roughness setting, e.g. glossy coating, metal, rough glass etc.
  • Specular rays include any "sharp" specular reflection/transmission without a roughness setting (glass and mirror materials)