lighting techniques in nx render - design/lighting... · position distant lights evenly across the...
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© Copyright LightWork Design Ltd 2005
Lighting Techniques in NX RenderLighting Techniques in NX Render
© Copyright LightWork Design Ltd 2005
OverviewOverview
Light types in UG Shadows in UG General lighting principles 3 Point Lighting in NX
Render Creating a “photographic”
lighting studio in NX render How to approximate
exterior lighting in NXRender
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LighLightingting –– Light TypesLight Types
Light Types available in NX Render
Point
Ambient
Distant
Spot
Eye
View > Visualization > lights
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LightingLighting -- SpotSpot
Cone of light cast from a location in a specifieddirectionLocation specified by “to” and “from” pointsShadows can be castHighlight appearance can be controlledOften used as primary light source
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LightingLighting -- SpotSpot ParametersParameters
Cone Angle - Defines the extent of the highlightDelta Angle - bigger value/softer edgeBeam Fall off - max to min intensity across the highlight
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LightingLighting -- Spot ParametersSpot Parameters
Use Delta Angle to soften highlight edgesRapid Beam Fall-off can be too soft
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LightingLighting -- AmbientAmbient
Used to approximate reflected diffuse light in asceneColour and intensity parametersIndependent of visibility, therefore no shadowsAdds colour value to each pixelEffect can be controlled from material reflectanceToo high a value washes out images
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LightingLighting -- DistantDistant
Parallel rays of light as if from a distant sourceLocation independentDirection vector specified using to and from pointsShadows can be castUsed to simulate sunlight or as a secondary light
sourceDifficult to use with Showroom Environments and
scenery when shadows are enabled
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LightingLighting -- PointPoint
Finite source emits light in all directionsLocation specifiedCan be localised using fall-off
Shadows can be castGenerated in six directions – can be visually confusing
Good for representing the form of complex surfacesMainly used
Simulating lightbulbs Instead of ambient light for interiors For special effectsAs secondary light sources
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ShadowsShadows
Shadows are used toDefine spatial relationships of
objectsGive geometry a feeling of
weightAdd contrastAs a tool for composition
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ShadowsShadows –– Shadow Creation MethodsShadow Creation Methods
Shadow maps Pre processing step
Ray traced shadows Performed at render time
Two forms of shadow creation
Visualization > Advanced Lights > More Options > Detail
Shadow Map
Raytraced
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ShadowsShadows -- Shadow MapsShadow Maps
Produces soft edged shadows Softness can be controlled - Edges Accuracy is dependent on the map
resolution defined – Detail Memory overhead for storing depth
information
Pre-processing step - renders depthinformation into a buffer from thepoint of view of the light.
This information is used at rendertime to create the shadow
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ShadowsShadows -- Detail ParameterDetail Parameter
A common problemwith shadow mapsresults from theresolution being too low
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ShadowsShadows –– Detail ParameterDetail Parameter
Shadow Detail too coarse
Same Detail – smaller cone angle
Softness can make it worse
Detail increased
1. 3.
4.2.
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ShadowsShadows -- Ray traceRay tracedd
Produces hard edged shadows No memory overhead Highly accurate shadows from detailed
geometry Time overhead for tracing rays Render in Raytrace render mode to
anti-alias the shadow edges
Raytrace shadows are computed on the fly
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General principlesGeneral principles –– Modelling with LightModelling with Light
Aim of lighting is to convey 3D form in a 2D imageNeed to use a wide dynamic rangeShadows can increase contrast
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General principlesGeneral principles -- High KeyHigh KeyHigh Key lighting – Main areas of the image are light
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General principlesGeneral principles -- Low KeyLow Key
Low Key lighting – predominantly dark
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Light DirectionLight Direction –– FrontFront
Flattens out the object Flattens bump maps
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Light DirectionLight Direction -- SideSide
Shows form andtexture
Shadows prominent
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Light DirectionLight Direction -- BackBack
Produces silhouettes Can be used as rim
lights Shadows prominent
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Light DirectionLight Direction -- TopTop
Produces intenseshadow directlyunderneath the object
Good for makingobjects appear to beon the base plane
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Light DirectionLight Direction -- BelowBelow
Can be used at low levelto approximate lightbouncing off a baseplane
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User defined Light Studios in NX RenderUser defined Light Studios in NX Render
Part
LWK File
VisualisationTemplate
Part File
Part File
Creating a default light studio other than the supplied default lights willproduce better results
Provides a good basis to create a new lighting set-up
Save as a visualisation template to use with other parts
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Lighting techniquesLighting techniques -- 3 point lighting3 point lighting
Main lighting comesfrom the side light.Called the keylight.
3 point lighting is a techniqueused by photographers andfilm makers. The sameprinciples can be transferredto CG
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Lighting techniquesLighting techniques -- 3 point lighting3 point lighting
Lower intensity lightfrom opposite sidecalled the fill light
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Lighting techniquesLighting techniques -- 3 point lighting3 point lighting
Backlight to illuminatethe “rim” of theobjects
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Lighting techniquesLighting techniques –– 3 point lighting3 point lighting
Combinedtogether
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Lighting techniquesLighting techniques -- Photographic lightPhotographic light
Photographers use high intensity diffuse sources for “product”shots
Produce soft light and shadowsOften use shiny bases such as acrylic sheet underneath the subject
to produce reflections – called acrylic shadows
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Lighting techniquesLighting techniques -- photographic lightphotographic light
Flood reflectorangled
behind the subject
Reflecting cardleft and right
Camera/viewpoint
Reflecting cardfrontsubject
table
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Creating the studio in NXCreating the studio in NX -- GeometryGeometry
Reflective (raytraced) objects need objects to reflect so createscenery geometry like the real light studio
Create a base plane underneath the objectsCreate a plane for the area light above the objectsAngle the plane (about 45 degrees)Create reflector planes left and right
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Creating the studio in NXCreating the studio in NX
Apply separate visualisation materials to:The area light
Colour 1 ,1, 1 Reflectance: constant
Side reflectors colour 0,0,0 Reflectance: constant
the baseplane- Colour 1, 1, 1- Reflectance: matte
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Creating the studio in NXCreating the studio in NX -- LightsLights
Use an array of 9 spot lights parallel to each other toapproximate the large area light
Position behind the objects (relative to the view)Wide cone angle (120)Delta angle 0Beam falloff gradualShadows onDetail Extra FineEdges HardIntensity low (0.15)
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Creating the studio in NXCreating the studio in NX
Add 2 distant lights left andright pointing down at ashallow angle
Low intensity (0.2) No Shadows (scenery
geometry would castshadows)
Used to simulate reflectedlight
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Creating the studio in NXCreating the studio in NX
Add a distant light at the front Low intensity (0.2) Cast Shadows (no geometry
in the way) Used to simulate reflected
light
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Creating the studio in NXCreating the studio in NX
Render in NX
Soft, extendedshadows
to the front
Goodrenderingof form
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Creating the studio in NXCreating the studio in NX –– RaytraceRaytrace materialsmaterials
Apply a mirror reflectance to the baseA raytrace material on the objects (polished gold)
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Creating the studio in NXCreating the studio in NX
Set background to beray cube
Primary shader isplain white (thebackground in view)
Secondary is white(the background inreflection)
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Creating the studio in NXCreating the studio in NX
Effect of the Raycube secondarysetting
Clouds Plain - purpleGraduatedwhite to red
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Creating the studio in NXCreating the studio in NX
Effect of the side reflectorsSet to blackReflectance - constant
Graduatedwhite to red
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Creating a hemispherical lightCreating a hemispherical light
Distant lights are defined as a vector so this light studio willwork independently of model size
Illumination is constant from all directions around the model soit works well for animation and QTVR
Save in a Visualisation Template for use on different models
Approximation of a skylightusing an array of distant lights
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Creating a hemispherical lightCreating a hemispherical light
Position distant lights evenly across the surface of a virtualhemisphere (radius 1) pointing to the origin
Check shadows on for each lightSet the shadow softness to ultra softSet the shadow detail to StandardIntensity required depends on number of lights
– I used 17 lights with an intensity of 0.2
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Creating a hemispherical lightCreating a hemispherical light
The result is evenillumination withvery soft shadowsas if from anextended lightsource such as thesky
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Setting Light ColourSetting Light Colour
There are colour temp values for real light sourceswidely available
These can be converted to RGBBUT This does not take into account adaption and
will result in over-saturated colours
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Light ColourLight Colour
64, 156, 25520000Clear BlueSky
201, 226, 2557000Overcast Sky
255, 255, 2556000DirectSunlight
255, 255, 2515400High NoonSun
255, 250, 2445200Carbon Arc
255, 241, 2243200Halogen
255, 214, 1702850100WTungsten
255, 197, 143260040WTungsten
255, 147, 411900Candle
ColourRGB ValuesKelvin tempLight SourceThese RGBvalues willproduce amore realisticresult
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Setting Light ColourSetting Light Colour
212, 235, 255Cool White Fluorescent
244, 255, 250Standard Fluorescent
255, 244, 229Warm Fluorescent
ColourRGB ValuesLight Source
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Guidelines for LightingGuidelines for Lighting
Think of UG Render as a virtualphotographic studio
If in doubt start with 3 point lightingCreate re-usable photographic
studios in NX for specific effectsSoft lighting from extended sources
can be approximated by usingmultiple standard lights
You will need to consider creatinggeometry around reflective objects
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LightingLighting -- SummarySummary
Lots of lights soon becomeunmanageable so workwith one light at a timeduring set-up
Get as much contrast aspossible in your images
Take ideas from realphotographic lighting andphotographs