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This tube-shaped area light simulates a fluorescent or similar-s= haped light source.
Its usage includes illuminating objects, simulating commercial lighting = used in many buildings, linear lights, fluorescent lights, and light panels= . This is also used for making lightsabers.
These parameters are the same as PxrRectLight and vice versa (with the exc= eption of mapping capability). Because of this, the examples are mostly the= same.
You will see mention of "non-physi= cal" controls. These controls are designed to help artists make art-directe= d imagery by ignoring certain laws of physics we usually simulate.= p>
Avoid scaling the cylinder in such a way that the cross-section is no lo= nger a circle. Essentially, do not "squash" the light by flattening it. You= can scale it uniformly or by length.
Intensity
Scales the contribution of this light linearly. The li= ght intensity is computed using physical falloff. Below the Intensi= ty parameter increases by 1.0 each render.
Exposure
Specifies the exposure of the area light as a power of= 2. Increasing the exposure by 1 will double the energy emitted by the ligh= t source. A value of 0 produces an intensity of 1 at the source, = -1 produces 0.5. Real-world ligh= ting has high energies and typical exposures are low values while you may h= ave to type a really large number for equivalent Inten= sity . This is also comforta= ble for artists familiar with photographic measurements. The intensity is r= eset to 1.0 so the result starts darker than above because of the physical = falloff of the light.
Color
The color of the emitted light.
Enable Temperature
Turns color temperature on or off.=
Color Temperature
The effect will be less pronounced on fully saturated monochromatic ligh= ts. Defaults to 6500K, which should be very close to white on most monitors= (D65 illuminant used by sRGB and Rec 709).
Primary Visibility
The light isn't directly visible to the camera by default. Turning this = on makes it visible and can be written to an LPE using the emission token, = 'O'
Emission Focus
Off-axis cosine power exponent to shape the emission. This controls the&= nbsp;spread of the light. Higher numbers will start focusing = the light towards the center and thus narrowing the light spread.
Emission Focus Tint
Off-axis light color tint. This tints the emission in the falloff region= starting from the off-angle direction of the light towards the center. By = default, the tint color is black (none). In addition to tinting, values gre= ater than white will also increase the intensity of the falloff region.&nbs= p;Notice when using White the emission focus nearly appears to be off.
Specular Amount
Amount of specular light that is emitted. This is a non-physical co= ntrol. You could use a light with Specular = Amount 0.0 to act purely as a source of diffuse light = for your scene objects and avoid adding highlights. This scene h= as subtle reflections but you can notice the light disappears from the = ;reflection in the chrome ball far right.
Diffuse Amount
Amount of diffuse light that is emitted. This is a non-physical control.= You could use a light with Diffuse Amount<= /strong> 0.0 to act purely as a source of highlights for your s= cene objects.
Intensity Near Dist
Near distance between the point being illuminated and the light at which= the sample doesn't get brighter. This may help you avoid hot spots and sam= pling issues where a light is near a surface. These values are based on you= r scene scale/distance so this is just an example.
Specular Near Dist (available in 24.5)
Near distance between the point with specular shading being illuminated = and the light at which the sample doesn't get brighter. This may help you a= void hot spots and sampling issues where a light is near a specular surface= . Note that this value will not apply to lights as seen fr= om the camera. Below, the right sphere h= as a distance of 0.0, 5.0, and finally 10.0. These values are based on your= scene scale/distance so this is just an example.
&nb= sp;  = ;
Diffuse Near Dist (available in 24.5)
Near distance between the point with diffuse shading being illuminated a= nd the light at which the sample doesn't get brighter. This may help you av= oid hot spots and sampling issues where a light is near a diffuse surface. = Note that this value will not apply to lights as seen from= the camera. Below, the left sphere has = a distance of 0.0, 5.0, and = finally 10.0. These values are based on your scene scale/distance so this i= s just an example.
&nb= sp;  = ;
Cone Angle
Angle of the virtual flaps on the light to turn it into a spotlight.&nbs= p;This does not affect IES Profiles (should you be using one).
Cone Softness
Softness of the cut-off of the Cone Angle. The regular = range is from 0 (hard cut-off) to 1 (smooth transition), but it can be set = higher than 1 for additional gradation. Above in the Cone Angle you notice how hard the edges look, this parameter improves that resu= lt to be more pleasing.
IES Profile
Name of an IES light profile. Below makes use of three different IES pro= files and some dark mood lighting.
Profile Scale
Rescales the angular distribution of the IES profiles. Values less than = 0 specify that the profile represents less angular coverage, and will effec= tively increase the size of the projected profile. Defaults to 0 for full c= overage (no scaling).
All shadow parameters will be igno= red if the light's Trace Light Paths is enabled in Advanced. The below optio= ns are all non-physical controls when used out of their default state. If&n= bsp; Trace Light Paths is enabled then their physical nature is enforced.= p>
Enable Shadows
Enable raytraced shadows.= p>
Shadow Color
The color of the shadows cast by e= mitted light.
Shadow Max Distance
The maximum distance of the shadow= starting from the position of the point being shaded. -1.0 is unset which = will use the distance between the point being shaded and the point on the l= ight. You may use this control to artificially reduce the distance shadows = are cast. This may also increase render speed by not calculating shadows ou= tside this distance. Here it's used to remove the shadow off the back wall = from the flashbulb effect of the light.
Shadow Falloff
The distance from the light at whi= ch shadow falloff begins. -1.0 turns off shadow falloff. This is used along= with Shadow Max Distance to create a false fade for shadows that are reduce= d or cut off by the Shadow Max Distance parameter. Below is an example with = both parameters being used and the falloff is increased. Note this paramete= r may impact performance on complex lighting setups.
Shadow Falloff Gamma
The gamma of the shadow strength i= n the falloff zone. This requires the use of Shadow Ma= x Distance and = Shadow Falloff .
Trace Subset
Set of geometry to consider for traced shadow intersection. If this is n= ot specified, all geometry are considered for traced shadow intersection.= p>
Don't Trace Subset
Set of geometry to ignore for traced shadow intersection. If this is not= specified, all geometry is used for traced shadow intersection.
Normalize
When normalize is enabled, the amount of light contributed to the scene = will not change as you scale the light source. This makes it easier to adju= st highlight size without changing scene lighting.
Trace Light Paths
Enable light and photon tracing fr= om this light. This value enforces a physically-based light and as a side-e= ffect disables the above Shadows controls. Users may use this feature to se= lectively decide which lights emit photons when using the PxrVCM or PxrUnif= ied Integrators.
Thin Shadow
Enable thin shadow and disable ref= raction caustics for this light. This parameter will ignored if Trace Light Paths = is enabled. This is a non-physical control that creates "fake" colore= d shadows for transmissive objects without needing to generate photons for = caustics. Notice we lose the colored shadows and interior colored reflectio= n choosing Off, but we gain some render speed instead.
Visible in Refraction
Make a light visible through transmission effects like glass and windows= by turning this on.
Manifold Walk
Used with the PxrUnified Integrator and enabling Enable Man= ifold Walk to create inexpensive caustics. Note: You must dis= able Thin Shadows
Manifold Walk Exclude Group
Used with the PxrUnified Integrator and enabling Enable Man= ifold Walk, this trace set is ignored during manifold exploration = to avoid stopping or shadowing manifold exploration rays
Light Samples
Specifies an override of the numbe= r of light samples to be taken for this light source. If set to something o= ther than zero, it will override the sampling performed by the integrator a= nd can result in a performance impact. It's recommended to leave this at th= e default unless you experience unsolvable noise from the light.
Light Group
Specify the light group name used for light group LPEs. This is useful t= o generate per-light AOVs for later adjustment in compositing.
Importance Multiplier
Rather than setting explicit Light Samples, users can change the amount = of samples the light will be assigned internally by changing this value. Re= nderMan creates a set of samples at render time for all lights in the scene= and changing this value rebalances the samples across the lights. Note tha= t increasing this value will cause more sample= s to be selected from this light while reducing it for others in the scene.= Lower than the default will decrease the samples while = providing more to others in the scene.