RedSDK Rectangular Physical Light Luminance
About Rectangular Physical LightFrom the help files - A Physical Rectangle light uses the definition of light sources from physical parameters issued from lamp manufacturers. A Physical Rectangle light uses a rectangle that defines the light surface that will emit light in the scene.
Physical lights are rendered on the CPU using sampling and are approximated on the GPU. There are two possible approximations for a physical light on the GPU:
- If the physical light is linked to a rectangular mesh, then the physical light is automatically turned into an Area light.
- If the physical light is linked to a mesh with any other geometric shape, then the physical light is automatically turned into a Point light.
PARAMETERSThe rectangular Physical light has more parameters than the standard physical light, it has position and direction which can be set.
- Power â€“ Sets the power of the light in Watts.
- Luminous Efficiency â€“ Sets the luminous efficiency of the light in percentage (%).
- Intensity decay â€“ Set the rate at which the lights power diminishes.
- Color â€“ Sets the color of the light.
- Color Temperature â€“ Alternate color value which supports definition of the color by temperature in Kelvin.
- Color Affect â€“ Sets the relative intensity (power) of the color light.
- Samples Count â€“ Sets the maximum number of light samples.
- Double Sided - sets whether the light will emit from one face or opposite faces, it is simply personal preference as to which works out best.
- Pos â€“ Sets the X,Y,Z position of the light relative to the object to which it is attached.
- Dir â€“ Sets the X,Y,Z direction of the light relative to the position.
If the luminance is attached to a fixed rendered object, many times one cannot rotate the source because this would alter the way the material looks, therefore DIR allows the light direction to be altered without affecting the source.
- Top â€“ Defines a second axis which is perpendicular to the direction, used for the rotation, if the lights display is not circular.
- Samples Count â€“ Sets the number of samples used to populate the light surface. Must be greater than 0
- Width â€“ Sets the width of the defining rectangle.
- Height â€“ Sets the height of the defining rectangle.
- Shadows â€“ Sets whether the light will generate shadows, or not.
- Shadow Color â€“ Specifies the color of shadows created by the light.
- Shadow Map - Shadow maps are generated by testing whether or not each specific pixel is visible from the light source. This is accomplished by comparing each pixel to a depth image (z-buffer) of the light source's view, stored in the form of a texture file. Shadow maps can accelerate the rendering of shadows, but usually as the cost of some quality
In the image below, the shadow is too dark behing the glasses.
- Texture File Name â€“ Rather than using a single constant color for the whole light, you can setup a texture from which light color will be read. Using a texture, you can simulate projectors or complex light filters.
- IES File Name â€“ Manufacturers measure the behavior of their bulbs and store their directional contribution into IES files. Those files are available for most of the bulb models directly from the manufacturers' web sites. Even if IES files store information about the shape of the emitter, they are not used here.
- Caustics â€“ Specifies whether the light will generate caustic effects.
- Visible Geometry - Specifies whether the physical geometry of the associate 3D objects will be seen.
- Intensity Decay - allows alteration to the quadratic equation.
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RedSDK Luminance Reference