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Lighting : Lighting February 2016 - Vol 36 Issue 1
Contents
42 LIGHTING MAGAZINE | February/March 2016 is.called.Bloom Unit,.which.is.a.plug-in.for. SketchUp..Similar.product.versions.will.also.soon. be.available.for.both.Revit.and.ArchiCAD. WHAT IS NEEDED IN LIGHTING CALCULATION AND VISUALISATION SOFTWARE When.we.view.a.scene,.we.cannot.see.the.light. itself,.only.the.luminances.of.the.surfaces.that. reflect.this.light..So,.the.light.sources.only.play.. a.small.role.in.this.calculation.process,.since. once.the.emitted.light.from.the.luminaires. strikes.the.first.set.of.surfaces,.the.luminaires. play.no.further.part.in.the.complex.calculation. process.that.follows.. For.physically.accurate.and.photorealistic. imagery,.complex.algorithms.are.used..Not.. only.is.it.necessary.to.calculate.the.precise. angle,.intensity.and.colour.of.the.incoming. light.from.the.huge.number.of.source.elements. throughout.the.scene,.but.we.also.need.to. precisely.calculate.all.the.directions,.intensities. and.colour.of.the.light.emitted.from.each. component.(see.Figure.1). The.number.of.calculations.increases. exponentially.as.the.huge.number.of.surface/ material.segments.throughout.the.scene. continue.to.inter-reflect.light.within.the.space.. At.the.core.is.the.light.transport.calculation.. for.each.and.every.material.on.every.segment. in.the.scene;.each.material.definition.can.involve. hundreds.of.parameters.covering.a.huge.range. of.properties,.such.as.reflectance,.refraction,. transparency,.translucency.and.sub-surface. scattering,.to.name.a.few. The.problem.for.the.lighting.design. community.is.that.most.software.packages. cannot.render.realistic.appearances.of.(much. less.proper.reflected.light.contributions.from). finishes.such.as.aluminium,.stainless.steel,. ceramic.tiles,.any.type.of.gloss.finish,.translucent. materials.and.many.others.. The.three.missing.elements.from.most. lighting.visualisation.software.concern.the. diffuse.transmission.of.light,.specular.reflection. and.daylight’s.contribution.to.the.lighting.. (and.appearance)..These.are.discussed.below.. Diffuse Transmission The.first.missing.feature.is.the.ability.to. calculate.diffuse.transmission..In.Figure.2. sunlight.being.scattered.as.it.passes.through. Figure 2. This bedroom has two translucent skylights (top) that diffusely light the room surfaces, shown realistically in the centre image. The bottom image shows the incorrect effect without diffusion. Figure 1. A photorealistic and photometrically accurate image of a daylit child’s bedroom, showing the effects of directional light, fine detail (eg, the venetian blinds) and the semigloss walls. This and the other images were produced on a laptop using SketchUp with the Bloom Unit plug-in. USA / MIDDLE EAST / ASIA PACIFIC / EUROPE © COPYRIGHT FYNTRIM PTY LTD 2016
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Lighting December 2015 - Vol 35 Issue 6
Lighting April 2016 - Vol 36 Issue 2
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