Annotation:
The color setting of the regular light options tints the shading of the Nodal Area Light. The arrows on the "surface" of the Nodal Area Light OpenGL preview point in the direction of the right and up vectors of that very light, so that you alway know how it is oriented. Another IMPORTANT fact is that at lighting time ONLY raycasting is available to nodes. As a consequence nodes, which use rayshading or raytracing, should be avoided.
Quality:
Sets the quality of the Nodal Area Light. The number of resulting samples is the square of this value.
Edit Nodes:
Opens up the node editor for this light.
Double Sided:
Makes the light double sided.
Root Node:
Color: The output color for the current light sample.
Intensity: The intensity for the current sample. Note: This usually is a value of 1.0 / (Quality*Quality), as all the intensities are summed up. So if you want to alter this value, you should use it in connection with the Quality output of the Info Node (see below).
Attenuation: The shadow attenuation for the current sample.
Info Node:
Quality: Normally the same as the quality setting in the light panel, but under certain circumstances (e.g. preprocessing, sampled shaders) it might be a different value (most likely 1) to avoid slowdowns.
Light Position: The light position in world coordinates (= the center of the Nodal Area Light).
Origin: World coordinates from where the current light sample comes from on the "surface" of the Nodal Area Light.
Direction: The normalized direction of that sample (= (World Spot - Origin) / Length).
World Spot: World coordinates from where in the scene the light is sampled.
U & V: The UV coordinates of the current sample on the light with <0, 0> being in the center.
Distance: The distance between Origin and World Spot.
Cosine: Cosine between the light "normal" (= forward vector) and Direction.
Light Side: Which side of the light is being sampled: If it is the front it equals 1, otherwise it is 0.
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