Radiance IES User Guide

Transcription

1 Radiance IES User Guide IES Virtual Environment Copyright 2016 Integrated Environmental Solutions Limited. All rights reserved. No part of the manual is to be copied or reproduced in any form without the express agreement of Integrated Environmental Solutions Limited.

2 Contents 1. Introduction Images Tab Create Images Image Quality Generate View Images Sky/Eye Tab Sky Time/Date Eye View Position Surface Properties Tab Material Surface Properties Calculating Reflectance Calculating Transmissivity Assigning Surfaces Pattern Properties Image Properties BSDF properties Luminaire Settings Tab Sensor Settings Tab Sensor Positions Sensor Outputs Files/Queues Tab Octree Files and Project Data Files Image Queue Dynamic Simulation Room Simulation Results WP Grid Room and Files Results and Statistics Miscellaneous Notes Glare Daylight Factor Sky Component/Vertical Sky Component Material Types Design Tips Simulation Tips Design Inertia Iterate Virtual Camera Design Day(s)/ Design Time(s) Design Sky Control of Simulations Saving Parameters VE 2015 Model Viewer II (in VistaPro) 2

3 11.6. Daylight Factor Contour Images Ground Ambient Value Exposure Keyboard Options Radiance Publications Introduction Radiance is a software package developed by the Lighting Systems Research group at the Lawrence Berkeley Laboratory in California, USA. Radiance was developed as a research tool for predicting the distribution of visible radiation in illuminated spaces. A three-dimensional geometric model of the physical environment is used, and a default material or map file detailing the spectral radiance values into a photo-realistic colour image. It can be used to calculate lighting levels, Daylight Factors or Glare for daylight and/or artificial lighting. Radiance is internationally recognised as one of the leading lighting simulation tools available. IES have been using Radiance over a wide range of commercial projects for many years and to facilitate this work IES have integrated Radiance into the Virtual Environment. The latest version of this integration RadianceIES provides users with even greater ease of use through its customised Graphical User Interface (known as the Virtual Environment Framework), which integrates with all the IES software packages (SunCast, Apache, etc.). VE 2015 Model Viewer II (in VistaPro) 3

4 Everything you want to know about Radiance can be found in the book Rendering with Radiance by Greg Ward Larson & Rob Shakespeare, published by Morgan Kaufmann Publishers. More introductory information can be found in the supplementary IES document Radiance Overview. Radiance is started by clicking the RadianceIES button from the Lighting section of the Application Selector. VE 2015 Model Viewer II (in VistaPro) 4

5 The Radiance view consists of the usual Model Browser and Viewport with a series of tabs at the bottom of the page. These tabs have been categorised as follows - Images Sky/Eye Surface Properties Component Settings Luminaire Settings Sensor Settings Files/Queues Dynamic Simulation WP Grid AOI VSC The function and data requirements for these tabs are described below. Site location data is inherited from ModelIT but can be changed in Radiance by clicking the location icon in the bottom right corner of the screen. This will open ApLocate dialog where the location and weather data can be changed VE 2015 Model Viewer II (in VistaPro) 5

6 Documentation on the WP Grid, AOI and VSC tabs is in a separate document. 2. Images Tab On this tab we have two sections: Create Images View images 2.1. Create Images This section allows the user to set the image type (Luminance, Illuminance or Illuminance - working plane), the quality of the image, and the Simulate button, allowing VE 2015 Model Viewer II (in VistaPro) 6

7 the user to start a simulation. The quality settings can be saved to a file or retrieved from a file (*.rdp file). To improve the simulation quality an Overture simulation can now be performed (this is similar to doing a pre-simulation for thermal modelling). This option is switched ON by default. VE 2015 Model Viewer II (in VistaPro) 7

8 Image Quality The initial quality setting is selected from the slider bar, if the Customise check box is ticked then the slider bar is replaced by two buttons; Customise and SC/VSC. The "Customise" button opens a dialog box to allow the setting of individual simulation parameters. This feature is best left to the more experienced user. The "SC/VSC" button opens the same dialog box but with the "Ambient bounces" parameter adjusted to generate the Sky Component (Vertical Sky Component) values. Note: The "Ambient Value" parameters are new to this tab and should be left at 0.0 for most simulations. VE 2015 Model Viewer II (in VistaPro) 8

9 Generate Using the radio buttons provided, we can choose to generate one of the following types of images: Luminance - to generate a photo-realistic image or to analyse glare. Illuminance - to determine LUX levels or Daylight Factors. Illuminance-working plane - as above, except on a notional working plane specified by the user. Note the working plane height is 0.85m by default. The user can set this height by selecting the zone of interest and going to RadianceIES (main menu bar) > Preferences > Working Plane 2.2. View Images In this section we can select from the list of images - When a picture is selected and the Show Thumbnail option is active the image is shown. Alternatively the dialog in the list box changes to show the picture information VE 2015 Model Viewer II (in VistaPro) 9

10 (note that for an illuminance image using the CIE Overcast sky the Ground Ambient value is shown (this is the 100% DF value). The Re-name button pops-up a window to allow the user to rename the selected picture. The Delete button pops-up a window to confirm the deletion of the selected picture. Any associated files are also deleted e.g. batch file, glare file. The Browse button allows the user to select images from other project directories. The View button displays the selected picture using the Picture viewing module, which can also be run as a separate program. The functions available in the image viewing window are explained in the section Image Display. By clicking anywhere on an image the luminance/illuminance at that point is displayed. These values can be removed by right clicking the value. Luminance/illuminance levels can be shown as contours to aid analysis of the image. Luminance images can be used to analyse glare sources. VE 2015 Model Viewer II (in VistaPro) 10

11 3. Sky/Eye Tab On this tab we have two sections: Sky Time/Date View 3.1. Sky Time/Date This allows the user to select the required date, time and sky conditions. The following standard sky conditions are available: The most frequently used sky conditions are: Sunny sky - for glare analysis Standard CIE overcast sky - for Lux levels and Daylight Factors VE 2015 Model Viewer II (in VistaPro) 11

12 3.2. Eye View Position This allows the user to select the view type, eye and focus positions, picture size and horizontal and vertical angles/sizes. The default view is to add 10% to the bounding box of the model and set the focus position to the centre of the model. If a zone is selected, then the eye and focus position change to inside the zone. The Lock selectors can be used to maintain a fixed eye/focus position. The Eye view position is the point from which the image is taken (i.e. where a camera would be placed) and the Focus view position sets the point towards which the camera would be directed. They are easier to set up when the model is in plan view. The Horiz( ) and Vert ( ) are the angles of which the images are taken they can be adjust manually or alternatively each view option has its own default angles. There are four view options - Perspective Plan Hemispherical Fish-eye Angular Fish-eye The "Hemispherical Fish-eye" view can have a maximum angle of 180 and the "Angular Fish-eye" up to 360, for both these options a single angle is defined. A Perspective view allows the user to define both the eye and the focus positions. This can be done by either double right-clicking the mouse on the new Eye/Focus position and choosing Set Eye/Focus Position option or by changing the x, y and z values. VE 2015 Model Viewer II (in VistaPro) 12

13 The Get Position button displays the building in Model Viewer mode and allows selecting the required position. You can move around the model in that view using W (zoom in), S (zoom out), A (left), D (right), E (up) and C (down) keys on your keyboard. Once the required view is set up just close the Model Viewer mode. If a "Plan" view is selected then the window changes: VE 2015 Model Viewer II (in VistaPro) 13

14 The Focus Position data is no longer required. Also note that the horizontal and vertical dimensions change from angles to metres (i.e. the width and height of the image). The default is to add 0.5m to the bounds of the room or model; if the room has a complex shape the generated image will include other zone(s). The Save view file button allows the user to save the currently displayed View options, i.e. view position and parameters. The Open view file button allows us to retrieve the view previously saved. The Save sky file button allows the user to save the currently displayed Sky options. The Open sky file button allows us to retrieve the values for previously saved data. By default the sky file has an automatically generated name of the following format: Sep21_1200_cie.sky, this has a 3 character mnemonic for the month, the day of the month, the time and the sky condition used. When an image is created this information is stored in the image header and displayed in the image summary information. See View Images. The mnemonics used for the different sky conditions are as follows: ss = sunny sky. cie = CIE overcast sky. cs = clear sky. u = uniform sky. i = intermediate sky without sun. is = intermediate sky with sun. 4. Surface Properties Tab VE 2015 Model Viewer II (in VistaPro) 14

15 This tab is broken down into four sections: Material Surface Properties Pattern Properties Image Properties BSDF properties 4.1. Material Surface Properties This allows the user to edit the properties pertaining to the materials that are defined in the model. The Open and Save buttons will save and retrieve this data from a map file (the Assign button is defined below). This section shows a scrollable list of the defined materials and the properties that are assigned to each surface. To view or edit a material, double-click on the material name, the following dialog box opens. VE 2015 Model Viewer II (in VistaPro) 15

16 From this dialog box you can select from the list of materials or manually adjust the RGB values. The Type can be either plastic or metal. These both have the same set of parameters. If the Colour field is double-clicked then the following is displayed If the Define Custom Colours button is pressed then the window expands to the VE 2015 Model Viewer II (in VistaPro) 16

17 following Note: in Radiance colours are defined by RGB values in the range and the window above uses the integer range If a glass material is selected a different set of pre-defined options is displayed. VE 2015 Model Viewer II (in VistaPro) 17

18 The Type has a choice of three possible options - glass, trans or dielectric. These all have different parameters. See the section on Colour in Radiance of the Introduction to Lighting document, Page Calculating Reflectance For solid materials (plastic and metal) the Edit/Select Material pop-up window has a Reflectance button, clicking this will calculate and display the reflectance value 4.3. Calculating Transmissivity If the user has a transmittance value and wishes to know the transmissivity value of this, then they can simply click the button labelled Tn => tn, which displays the Calculate Transmissivity dialog box below The user enters their value in the Transmittance field and then clicks the Calculate button. The resultant transmissivity value will now be displayed in the Transmissivity field. Should the user wish to use this value for the selected glazed surface, then click OK and the R-trns, G-trns and B-trns fields in the grid will be updated to reflect this Assigning Surfaces The Assign button is used to change the assignment of selected objects VE 2015 Model Viewer II (in VistaPro) 18

19 The required Category is selected and the available Types are highlighted, the user then picks the replacement Type. The Replace button will make the required change. The New surface type button pops-up a window which allows the user to create a new Type in the selected Category The user must give each New surface type a unique name. This will appear in the list of replaceable surface types, which can be assigned to the selected surface(s) Pattern Properties This allows the user to create/delete/edit the parameter definitions for patterns. Click the + button to add a new pattern, enter pattern name (this name cannot contain spaces). VE 2015 Model Viewer II (in VistaPro) 19

20 When OK is clicked the Edit Pattern dialog pops up where the pattern properties can be adjusted and the pattern is added to the grid. Once a pattern has been added, the user can then assign this pattern to the modifier field of a surface. To assign a pattern to a given surface, the user should select the surface from the list provided (Material surface properties) and double click the Modifier field. They will now see a drop down list of all available patterns in the project. Simply select the pattern you wish to apply to that selected surface. VE 2015 Model Viewer II (in VistaPro) 20

21 The - button will delete the selected pattern and any materials which reference this pattern will revert to the void modifier Image Properties This allows the user to create/delete/edit the definitions of images. The + and - buttons work exactly as for patterns creating and deleting images. The "Convert" button allows the user to convert a "tiff" file into a Radiance "pic" file which can be attached as an image (other formats can be translated to "tiff" in most painting software packages). To edit the other parameters the following window is displayed when the selected item is double clicked - VE 2015 Model Viewer II (in VistaPro) 21

22 For an explanation of these parameters and the other hidden parameters (active in "Picture" mode) see the document Image Parameters BSDF properties BSDF stands for bidirectional scattering distribution function. Essentially, it is a mathematical function that determines the probability that a specific ray of light will be reflected (scattered) at a given angle. In short, the BSDF means that the light coming through the glass or shade will be scattered. The type of glass or shade determines the distribution function, which in turn determines how the light is scattered and how the material appears. There are two ways of using a BSDF in the VE and it depends on what the BSDF is meant to model - if the BSDF represents a glazing system then it can be applied to a glass material (Scenario 1), if it represents a blind or other device it can be applied to a component that the user has created (Scenario 2). Note: it is up to the User to provide their own BSDF data file (xml). BSDF modifiers can only be used for glass materials. Scenario 1: modify all the glazing to use a BSDF material Go into the "Surface Properties" tab. VE 2015 Model Viewer II (in VistaPro) 22

23 Create a new BSDF property (using "+" button). After entering name, "Edit BSDF" dialog opens. Use the "Browse" button to find the "xml" file that defines the BSDF. The BSDF description is now loaded. This can now be applied to the glazing by changing the "Modifier". VE 2015 Model Viewer II (in VistaPro) 23

24 When we now perform a simulation the BSDF definition will be substituted for all the "External Glazing" - here's a simulation for the ground floor of the test model: Compared with the "default" image (without the BSDF): VE 2015 Model Viewer II (in VistaPro) 24

25 If required create an alternative "replacement surface type" using the "Assign" option. For example, in this zone we have two windows with different glazing VE 2015 Model Viewer II (in VistaPro) 25

26 In this example we would assign the BSDF to the "Louvre_glazing" and not to the "External Glazing" - i.e. the "External Glazing" modifier would be "void" and the "Louvre_glazing" modifier would be set to "glass_bsdf". Scenario 2: Component to represent a blind added to one of the zones. In this scenario we have to edit the material property for the Component Note: the "modifier" can only see the BSDFs when the material property is set to "glass". Also note that the components have to be switched ON (in "Component Settings" tab). When used in this mode the properties for the component are substituted for the BSDF, VE 2015 Model Viewer II (in VistaPro) 26

27 so it is irrelevant what properties are defined. "Default" image with no blind Image with solid blind image with BSDF blind VE 2015 Model Viewer II (in VistaPro) 27

28 The images look similar but the lux levels at back of room are higher for the BSDF blind. 5. Luminaire Settings Tab Luminaire properties are defined using the LightPro application. The Use Luminaires? switch is used to activate the use of luminaires; the Daylight off? switch is then available. The options available in the Switching allow for quick selection of default scenarios e.g. all lights ON, only lights in a selected room ON. When a zone with lights is selected, the list is updated: Individual lights can be switched ON or OFF using the button to the left of each luminaire description. The luminaire positions are also drawn in the canvas window. The Summary button generates a window detailing what luminaires are defined in the model and the status of each. By default all lights are OFF until they are switched on. 6. Sensor Settings Tab VE 2015 Model Viewer II (in VistaPro) 28

29 6.1. Sensor Positions When Use Sensors option is ticked on for the first time the sensors are created - a warning message pops up. When you click OK you can choose where the sensors are placed (all zones in the model or selected zones only) and their position (ceiling pointing down or working plane pointing up) To position a sensor manually after default sensors have been placed, select the zone and go down one Level of Decomposition to Room Level, then a Double-Right mouse click in a position where you want to move a sensor to and select Set Sensor Position. In plan view set the x,y-position of the sensor then in any vertical view set the z- position. You can also set the sensor position by typing in the X, Y and Z position in the table. VE 2015 Model Viewer II (in VistaPro) 29

30 If a sensor is moved above the mid height of the room, a dialog will appear giving the option to make the sensor point downwards. Note: If a sensor is placed outside a zone then a warning message will pop up. This is allowed for recording the external light levels for reference in formula profiles. These sensors can be switched ON or OFF as required by selecting each zone individually and choosing ON or OFF in the switching section. Sensor settings can be saved using the "Save Sensors" button and reloaded using "Read Sensors". VE 2015 Model Viewer II (in VistaPro) 30

31 The Summary button will give a grid showing current sensor settings: Sensors that have been switched off are highlighted grey Sensor Outputs Radiance will perform simulations to determine illuminance at the sensor for given conditions. The "Apache" button will produce a model.ill file for use in the ApacheSim Radiance link. The "Radiance" button will produce the rad.ril file for use by radiance. There is an option to Use Custom parameters for Apache simulation and Dynamic simulation to tick on. The "Read Illum" button will read the illuminance file (rad.ril) and display the results in a table. VE 2015 Model Viewer II (in VistaPro) 31

32 The Copy and Text buttons will copy the grid image or grid text to the clipboard. The data can then be pasted in to a report or spreadsheet for further edit. Illuminance values over certain thresholds are highlighted as below: white green Red Lux < > 2000 Foot-Candles < > 200 Units can be changed between Lux and Foot-Candles. Statistics will also be output in the selected units. Component Settings Tab Components are created using the Component Modeller and assigned to zones in ModelIT (see the documentation on these modules for more information). The Use Components switch is used to activate the use of components. The options available in the Switching allow for quick selection of default scenarios e.g. all components OFF, only components in a selected room ON. When a zone with components is selected, the list is updated: Individual components can be switched ON or OFF using the button to the left of each component description. The components are also drawn in the canvas window if the user has gone down to the Component option at the Surface level of decomposition for the selected zone. The Summary button generates a window detailing what components are defined in the model and the status of each. VE 2015 Model Viewer II (in VistaPro) 32

33 7. Files/Queues Tab This tab can be broken down into three sections: Octree files Project Data Files Image Queue Octree Files and Project Data Files This allows the user to select which files are active (the octree files can be selected manually when the Use existing Octree file option is ticked off). Each button when activated pops-up a file browser to search for the required file type, e.g. sky file: VE 2015 Model Viewer II (in VistaPro) 33

34 When the user has selected all the required file options necessary for a simulation, this can be added to the simulation queue Image Queue This allows the user to queue simulations for future execution (e.g. you could create a queue for all rooms within a model and start the batch simulation without having to start each room separately). When the Add to queue + button is activated (after the input files have been provided) a batch process is created and added to the queue. When the Set start time button is clicked the following window is displayed: VE 2015 Model Viewer II (in VistaPro) 34

35 Once the start time is set the first batch process will start when the time is reached. If the start time is set to before the current time the batch process will start immediately. 8. Dynamic Simulation Dynamic daylight simulation is a new option within VE Radiance. The tab consists of three sections: Room Simulation Results 8.1. Room Once a room for simulation is selected this section displays information about the room s name and ID Simulation The "Run Simulation" button will be inactive until at least one zone is selected when VE 2015 Model Viewer II (in VistaPro) 35

36 clicked it will perform an annual simulation for each selected zone in turn - initially we recommend that this is done for a single zone. The Simulation Options button pops-up a dialog which allows the user to change the Working Plane height (default = 0.85) and the pitch of the grid (default = 0.5). The drop-down combo provides five time-step options: Full year: 365 days - full 365 days Monthly: 12 design days - use single "design" day per month (15th of Month) Weekly: every 7 days - use every 7th day (starting on 1st January) Full year: Weekdays only - Monday to Fridays over full year (assume 1st January is Monday) Full year: Holidays profile - Simulate for days that are not flagged as Holidays When Run simulation button is clicked progress bar will be activated to show that the rcontrib module is running When this process finishes the time series simulations will start running and the "Stop simulation" button will be shown along with a progress bar VE 2015 Model Viewer II (in VistaPro) 36

37 8.3. Results In the Results section the "Summary", "Process" and Time View buttons are inactive unless a single zone for which an annual results file exists. The Summary button displays some useful information on the results for the selected zone. The Time View button allows the user to extract data for a particular day of interest. VE 2015 Model Viewer II (in VistaPro) 37

38 The Process button pops-up the following dialog There are 3 options available: Annual Sunlight Exposure (ASE) - The ASE is a metric that describes the potential for visual discomfort in interior environments. It is defined as the percent of an analysis area that exceeds a specified illuminance level more than a specified number of hours. VE 2015 Model Viewer II (in VistaPro) 38

39 Spatial Daylight Autonomy (sda) - The sda is a metric describing annual sufficiency of daylight levels in interior environments. It is defined as the percent of an analysis area that meets a minimum illuminance level for a specified fraction of the operating hours per year. It reports a percentage of floor area that exceeds a specified illuminance level, e.g. 300 lux for a specified amount of annual hours, e.g. 50% of the hours from 8.00am to 6pm. Preferred threshold: sda300/50% 75% of analysis area Nominally acceptable threshold: sda300/50% 55% of analysis area Useful Daylight Illuminance (UDI) - The UDI is a metric where the illuminances are categorized into bands that are considered useful by occupants. These bands are, by default: less than fell short supplementary autonomous greater than exceeded With each of these options the user can select a specific analysis period from a dropdown menu, and for the UDI the threshold ranges can be edited (e.g. in some UDI studies the ranges are specified as less than 100, 100 to 2000 and greater than 2000 ). The threshold can be edited by enabling the Threshold check-box and clicking the Edit button this pops-up the following dialog: All of these options create a WP data file (or append data to an existing file) which VE 2015 Model Viewer II (in VistaPro) 39

40 the user can view by going into the WP Grid tab. Note: At time of writing the ASE and sda results processing is still in beta and will be improved further before the Beta label is removed from the Radiance interface. 9. WP Grid When a zone is selected all the data files that apply to this zone are displayed within the WP Grid tab. The tab includes four sections: Room Files Results Statistics 9.1. Room and Files The Room section displays information about the room that is currently selected (name and ID) and information about the working plane s height, grid size (pitch) and number of grid points in the x and y direction (#x, #y). They are displayed as information only and cannot be edited here. The Files section shows all the results files available. The data files are named using the "ZoneID" eight character label - if the data file has been created using the annual data then "_A" is appended to this label. The files can be selected at the Model level of decomposition. When a results file is selected all the available simulations are displayed in the "Results" section Results and Statistics When a simulation from the Results section is selected the results are displayed automatically at the Model level. The results values will be visible at the surface level of decomposition (down a level from a Model level). VE 2015 Model Viewer II (in VistaPro) 40

41 Going to a plan view displays the results in the defined colour bands. VE 2015 Model Viewer II (in VistaPro) 41

42 The Display Thresholds button pops-up the "Thresholds" dialog. This has a combo-box with four selections "Lux", "Daylight Factor", "Percentage" or Pass/Fail, the default ranges for these are: Low Medium High "Lux" "Daylight Factor" "Percentage" Pass/Fail n/a These thresholds can be changed in value or switched off to either three or two ranges, independently of the other ranges (except for Pass/Fail for obvious reasons). The + and - buttons change the size of the font that is used to display the data on the ViewPort. The AOI button will clip any cells that overlap the AOI, this can improve the display where you have non-orthogonal zones. The Filter check-box value, default to 1, will skip the display of cells data values on the ViewPort, i.e. a value of 1 will show every value, 2 every second value, and 0 will disable the values (this can be useful where the grid is very dense, but also tricky to get a sensible pattern). In this example the colour of the medium range has been changed and the high threshold has been set at 1000 Lux: VE 2015 Model Viewer II (in VistaPro) 42

43 The Tabulate output creates a text file showing the results for each grid point with a separate column for each results set [for comparison with DAYSIM]. It also calculates the average for each column. VE 2015 Model Viewer II (in VistaPro) 43

44 10. Miscellaneous Notes This section contains a series of useful notes; they may contain information which is repeated elsewhere in the documentation. 1. Glare 2. Daylight Factor 3. Sky Component 4. Material Types Glare Glare is caused by either or both the following: 1. Excessive luminance values in the field of view. 2. Too high luminance contrasts. Windows can have a high luminance compared with other luminances in a room. This gives a strong contrast from inside to outside, potentially causing glare. In Radiance simulations we may offset this by providing some internal background lighting. The strongest luminance source is the Sun, and if this in the field of view then glare is inevitable. The default glare threshold is calculated by the program to be 7 times the average luminance level, if required the user can specify an alternative value. We normally give the CIE Glare Index and the GUTH Visual Comfort Probability (% of people who are satisfied) as measures of glare. These values are calculated at fixed angles to the left and right of the centre of focus (usually at 10 degree intervals from 60 to +60 degrees), see figure below: VE 2015 Model Viewer II (in VistaPro) 44

45 10.2. Daylight Factor The ratio of the illuminance at a point on a given plane within an interior due to the light received directly and indirectly from a sky of assumed or known luminance distribution, to that on a horizontal plane due to an unobstructed hemisphere of this sky. Direct sunlight is excluded from both values of illuminance (i.e. CIE Overcast Sky). E = illuminance on unobstructed plane e = illuminance at point in interior VE 2015 Model Viewer II (in VistaPro) 45

46 Daylight Factor = e/e (often expressed as a percentage) Illuminance is measured in LUX Sky Component/Vertical Sky Component The ratio of the illuminance at a point on a given plane within an interior due to the light received directly from a sky of assumed or known luminance distribution, to that on a horizontal plane due to an unobstructed hemisphere of this sky. Direct sunlight is excluded from both values of illuminance (i.e. CIE Overcast Sky). Note this is the same as the Daylight Factor except the indirect component has been removed. E = illuminance on unobstructed plane e = illuminance at point in interior Sky Component = e/e (often expressed as a percentage) Vertical Sky Component = v/e Material Types Plastic - a plastic surface has a colour associated with diffusely reflected radiation, but the specular component is uncoloured. Most materials fall into this category painted VE 2015 Model Viewer II (in VistaPro) 46

47 surfaces, wood, stone, plastic. Metal - this material type differs from that of plastic in that the specular component is modified by the material colour. Both these materials have five parameters: 1. Reflectance value for Red, Reflectance value for Green, Reflectance value for Blue, Specularity value, Roughness value, The extremes of 0.0 and 1.0 for the reflectance values do not occur in nature. Plastic materials are generally not very reflective and the specularity value is usually in the range Metal materials are reflective and the usual range is Plastic materials generally have a roughness in the range Metal materials have range of There are a number of different material types which can be used for window constructions (dielectric, trans, glass), with the simplest of these being glass. This is a specially modified dielectric and has a standard refractive index of 1.52 and all that needs to be defined is the transmission at normal incidence. The glass material has three parameters: Transmission value for Red, Transmission value for Green, Transmission value for Blue, The trans material has seven parameters: Reflectance value for Red, Reflectance value for Green, Reflectance value for Blue, Specularity value, Roughness value, Transmission value, Transmitted specularity value, VE 2015 Model Viewer II (in VistaPro) 47

48 11. Design Tips Simulation Tips Design Inertia When you first look at a design, you have what we call Design Inertia (unless you are making it up from your own ideas). This is the initial period when you start to look at the drawings, etc., before you decide how to build the model. Obviously this takes time, dependent on your own experience and the quality of the information you receive. Some planning will be required, but sometimes the best way to tackle this problem is to start to create the model with the understanding that you will have to go back and make changes. Starting with the bits of the model that are easiest to do is an obvious strategy, and by the time you get to the more difficult bits you at least have some context to work with. Radical revisions of a model should perhaps be saved as a new project then you can always go back a step Iterate Never spend a long time creating a model and then expect to get results out at the last minute (i.e. don't spend all week modelling and expect to get the correct results on Friday afternoon). Instead, iterate (design is iterative), do a bit of modelling then try a test simulation or two before refining the model. (This can also be true for most other areas of simulation). These test simulations should be inexpensive (i.e. Low/Medium quality), don t waste time waiting for a complex simulation, which you are going to throw away once you have refined the model. If you want a more complex simulation use what would be non-productive time to run the simulation i.e. lunchtime or overnight. Test simulations should be tidied up (i.e. deleted) when you have an improved simulation Virtual Camera It is important to understand that in Radiance we are simulating using a virtual camera and not trying to model the eye. This is why we often use the term photorealistic simulation (the eye is a very complex instrument compared to a camera) Design Day(s)/ Design Time(s) The software can perform analyses for any given date/time, so the biggest problem is deciding when to simulate and when not to simulate. Sometimes the client will specify exactly what they require, but mostly they will not. The obvious design days are - midsummer, the 21st June and mid-winter, the 21st December. These will give maximum and minimum levels of daylight. Another popular date is to pick a date half way between - the 21st of September (you should note that although there are slight differences in the Sun's path before and after the 21st June, for design purposes it is treated as symmetrical - this means that design studies are performed between 21st June and VE 2015 Model Viewer II (in VistaPro) 48

49 21st December and the other half of the year is ignored, probably because it is easier to think in terms of June to December rather than December to June ). As well as varying seasonally, daylight also varies daily. East facing rooms will get sunlight in the morning and West facing in the afternoon. The use of Daylight Factors can be useful for reducing the number of simulations (see below). Often you are presenting the worst case scenario, i.e. the minimum Lux, or the maximum glare Design Sky There are a number of different sky types in Radiance, but two are of particular importance - the CIE Overcast Sky and the Sunny Sky. The CIE Overcast Sky is used to give the worst case scenario (in design terms) for illuminance. The Sunny sky is used to give the worst case scenario for glare analysis (luminance images). There are some designers out there who believe that the CIE Overcast Sky has a fixed brightness (they usually quote 10,000 Lux), this is not the case, as the zenith brightness of the CIE Overcast Sky varies by Site Latitude, by season and by the time of the day. There is a mechanism in Radiance to define the zenith brightness, but this has not yet been implemented in the <VE> interface Control of Simulations It is very important to keep control of the simulation files (and other derived files, e.g. Lux contours, DF contours, etc.) you are creating, i.e. making sure the correct design dates/times and skies are used and the files you create are easily identifiable. There is nothing worse than to have twenty simulations with the default naming strategy i.e. test1, test2, test3, etc. Favour a naming strategy that identifies the images by using simple mnemonics e.g. v1_s12_c - view 1, September, 12 noon, CIE sky, or v4_d10_s - view 4, December, 10am, sunny sky. Using this technique I can decode any image by looking at the name. (Note the 21st of the month is implied as the date of the simulation in the above, but may also be part of the mnemonic) Saving Parameters When performing a series of simulations, it is important run them with the same accuracy setting, otherwise comparisons are meaningless. If you are using a default setting e.g. Medium, this is usually OK, however if the Customise option is used it can be difficult to remember exactly what was used when you come back to do more simulations at a later date Daylight Factor When using the CIE Overcast Sky it is possible to generate Daylight Factors, this value (expressed as a percentage) is the ratio of measured illuminance to a theoretical maximum on an unobstructed plane. This ratio is constant whatever the date/time of VE 2015 Model Viewer II (in VistaPro) 49

50 simulation, thus only one simulation is required to generate this data. See the separate note on Daylight Factors and Sky Components for more information Contour Images Saving lots of these images can clutter the image browser and the subdirectory, since these images can easily be regenerated, they can be thrown away after being saved into a report. The source images should be kept for future re-analysis Ground Ambient Value This is the theoretical maximum Lux value on an unobstructed plane using the CIE Overcast Sky i.e. this is the 100% DF value. Where applicable (CIE Overcast Sky) this value is displayed in the image header Exposure The default exposure is set to an average over the whole image, this can result in images which are either over-exposed or under-exposed with respect to some features which you may be interested in. Change the exposure either up or down as required Keyboard Options The following keyboard functions are available: Ctrl X delete selected Ctrl A activate Axonometric view Ctrl P activate Plan view Ctrl R activate Right view Ctrl L activate Left view Ctrl F activate Front view Ctrl B activate Back view Ctrl O open Model Ctrl N new Model Ctrl S save Model 12. Radiance Publications Grynberg, A. Validation of Radiance, Lawrence Berkeley Group, July Ward, G., A Contrast-Based Scalefactor for Luminance Display, Graphics Gems IV, Edited by Paul Heckbert, Academic Press VE 2015 Model Viewer II (in VistaPro) 50

51 Ward, G., Measuring and Modeling Anisotropic Reflection, Computer Graphics, Chicago, July Ward, G., The Radiance Lighting Simulation System, Global Illumination, Siggraph '92 Course Notes, organized by Paul Heckbert, July Ward, G., F. Rubinstein, R. Clear, A Ray Tracing Solution for Diffuse Interreflection, Computer Graphics, Vol. 22, No. 4, August VE 2015 Model Viewer II (in VistaPro) 51