We are trying to do a daylight analysis that includes some frosted glass or “kalwall” style skylights which diffuse the light into the space.  We can get the VLT (Visible Light Transmittance) values easy enough.  However, is there some way to accurately (or semi-accurately) account for the rays being dispersed and spread through the frosted glass? 

Simulating frosted glazing in 3ds Max Design for lighting analysis is doable.  You however need to know how to do it properly.  Here is how:

Some useful background information:

First, as opposed to Radiance, the A&D Material has a few internal “things” going on that you need to be aware.  The most important one is that the A&D Material performs internal energy conservation as follow:

Transmissivity wins over Specular Reflectivity which wins over Diffuse Reflectance.  On top of that, the Transmissivity is weighted against a Specular / Diffuse factor.  This factor is ruled by the Translucent color / weight controls in the interface.

In contrast, in Radiance, one can specify a material that is reflecting 100% diffuse and 100% specular while transmitting 100% of the light, leading to “creating” energy.  This is why the parameters of the Radiance materials cannot be plugged “as-is” in the A&D Material.

Translucent Panels:

We compared translucent glazing simulation in mental ray against radiance and measured data and got convincing results (see image) with the following settings:

Desired Diffuse Transmittance:  0.1621  (16.21% Diffuse – Diffuse Transmittance)

• Treat surface as a single polygon in the model
• A&D Diffuse Level:  0.0
• A&D Diffuse Color:  pitch black  (so no weighting is given to the diffuse reflectance)
• A&D Reflection | Reflectivity Level:  1.0
• A&D Reflection | Reflectivity Color:  pure white (the color is a multiplier, we need it to be 1.0 1.0 1.0)
• A&D Refraction |  Transparency Level:  1.0
• A&D Refraction | Transparency Color:  pure white (the color is a multiplier, we need it to be 1.0 1.0 1.0)
•  A&D Refraction | Translucency Checkbox : ON
• A&D Refraction | Translucency Weight: 1.0  (we want it fully translucent)
• A&D Refraction | Translucency Color:  0.1621 0.1621 0.1621 (the color is a multiplier, we need it to be set to the desied transmissivity level “as-is”, equally for all RGB components)
• BRDF | Custom Reflectivity Function: ON
• BRDF | 0 Deg Refl:  0.0
• BRDF | 90 Deg Refl:  1.0
• BRDF | Curve:  ~5  (we need to approximate a typical Fresnel curve)
• Advanced Rendering Options | Thin-Walled : ON

Some important notes: 

• While the illuminances will carry through properly on light meters, the glazing appearance may not look “natural” in “pretty picture renderings”.   It seems that there is currently a limitation with the appearance of the surface when it is hit by light:  its resulting luminance won’t be correct (AFAIK) so glare analysis based on luminance measurements won’t be convincing.
• The following image shows a graph comparing 3ds max, radiance and measured data.  Ignore the “3ds max 2009 SP1 Initial Submission” curve, this is representing a case where our material settings in 3ds Max where wrong, which we corrected later on – in fact, we forgot to turn off a layer so we had 2 panes of glass on top of each other…).  The green curve is what we need to look at….

My goal was to create a document where the main features of 3ds Max are grouped togheter to create daytime / night time renderings of buildings without overloading it with cumbersome step-by-step “click here/ click there” instructions.  It gives some tips and tricks around NPR (Non-PhotoRealistic) rendering as well.

Here it is:

mentalray.for.aec.renderings

This group maintains a database and publishes this data via a program called Optics 5. From Optics 5 you can then export a Radiance Material (*.rad file), which can be interpreted
as mental ray A&D Material parameters.

To convert Optics 5 data into A&D Material suitable for lighting analysis, export a glazing or glass definition as Radiance (*.rad) from Optics 5. You will find this command under File | Export to Radiance File.

Once the file is exported on disk, open it in Notepad and search for a section that looks like this:

void BRTDfunc B530_front
10
0.245 0.281 0.340
0.169 0.197 0.187
0 0 0

The color coefficients (RGB) for the ideal specular reflection corresponds to 0.245 0.281 0.340. The color coefficients for the ideal specular transmission corresponds to 0.169 0.197 0.187. Those values will need to be used as a basis for the mental ray A&D Material.

How to use the provided Microsoft Excel spreadsheet to convert to the mr A&D Material.

To correctly convert specular reflection and transmission from a Radiance material to a mr A&D Material, we need to take into account internal energy conservation methods that are built in the mr A&D Material that are not factored by the Radiance material. In other words, numbers can’t be “plugged-in” as is.

To help you with this task, we developed a Microsoft® Excel® software spreadsheet that will let you do this precisely. The spreadsheet can be downloaded here.

Limitations:

• The Radiance Materials exported from the Optics 5 database does not take into account angular dependency: A Fresnel falloff curve is assumed so metallic-coated glazing systems may be less precisely simulated.
• The Optics 5 database contains optical data measured spectrally. The exported Radiance materials and the A&D materials use RGB colors which are a crude approximation of the visible light spectrum. Therefore, lighting simulations are done within limitations of RGB colors.

It will also control Text objects to display the current Time and Date of the Daylight System:

Here is a video demonstrating its usage:

You can download the tool here.

1. In Revit, go in the 3D view you will export to FBX
2. Edit the Graphic Display Options
3. Specify a Location and Time that matches your project settings, for a single day:
4. Export to FBX
5. Import in 3ds Max

Your Daylight System should now match the Revit model in Location and Time.

]]> http://www.pfbreton.com/2009/10/translating-project-location-from-revit-to-3ds-max-via-fbx/feed/ 0 http://www.pfbreton.com/2009/10/material-name-and-layername-columns-in-scene-explorer/ http://www.pfbreton.com/2009/10/material-name-and-layername-columns-in-scene-explorer/#comments Mon, 12 Oct 2009 10:58:11 +0000 Pierre-Felix Breton http://www.pfbreton.com/?p=418 Have you ever wanted to display the material and layer names of objects in the 3ds Max Scene Explorer like this?

This can be done with a relatively simple MAXScript that you must install  under the \Scripts\Startup directory of your 3ds Max installation. 

By doing so, the script will execute each time 3ds Max is launched and will  instruct the Scene Explorer to fetch the Material and Layer names of your objects and create 2 new columns that you can drag and drop in place.

Click Here to Download the MAXScript

This video demonstrates how to do it:

This usually happens when you changed your Desktop Resolution and re-launched 3ds max.

What causes this problem?

The root of the  problem comes from the fact that last used dialog positions are stored in the 3dsmax.ini file.  Unfortunately,  none of theses dialog are coded in a way that they check if they are restored in a visible portion of the desktop, resulting in many cases as “out of reach” locations.

How to resolve the issue?

Until this bug get resolved in 3ds Max directly, there is a neat little utility that you can use to bring back “missing dialogs” in the visible portion of your screen:  SnapWindows.  Just run it while running 3ds Max to reset the  location of floating dialogs.

Click here to download the Wordfile.txt file for UltraEdit (Right Click | Save Target As…)

Install it in your UltraEdit installation folder:

When opening a mi file you should see something like this:

Always verify your data otherwise your project can go wrong – here are a couple advices on the topic:

IES file can contain wrong information: double check them!

I have once seen a manufacturer using the wrong values in their IES files.  I had to contact them and demonstrate that their data was wrong. It turned out that one of their engineer made a mistake with their database system where North American IES files where published using European measurements. That basically means that errors can come from anywhere in the process. Double check your work!

In the ideal scenario, you need to get a physical sample of the luminaire in your office, measure intensities with an illuminance meter and compare with the IES data provided to you in a simple test scene.

Do the numbers match up?  You are good to go. They don’t match up? Keep reading..

Check the 3ds Max scene units:

This is a typical trap: wrong units, wrong light intensities reported on light meters!

3ds Max and Revit has bugs too!

There is a issue  with the IES file reader that can affect you in rare occasions.  The bug has to do with a certain “feature” of the IES file format that some manufacturers rely on. Let me explain:

The IES file format is divided in two main sections: a header section and a data section:

In the header section, there is a special ”bit” that instruct the software to either use the “raw” data or apply a multiplier to it. For example, a manufacturer might have measured a luminaire only once with a 100W lamp in it. Knowing that the same luminaire with a 200W lamp** would emit twice as much light, the manufacturer could publish a different IES file based on the same measurements and simply state that the “raw” data should be multiplied by a factor of 2.0 by changing this special “bit” in the file as illustrated:

For some reason, 3ds Max and Revit are ignoring this multiplier and always read the “raw” data from the IES files, resulting in incorrect simulations. The work around is to use the built-in multiplier (dimmer) feature of the photometric lights:

Note about linear and area lights:

In many occurences, I am asked to perform lighting analysis reports in spaces designed with cove lights.  Unfortunately, this is still not possible to do precisely - and this problem has not been solved by the industry yet!

  There are currently two major problems with linear and area lights in lighting simulation softwares:

1. First, the IESNA standards for photometric measurements assumes that luminaires are measured from a certain distance, making any calculated points inside this distance mathematically inaccurate. If you search for “Near Field Photometry” or “Far Field Photometry”, you will find plently of information on the subject.
2. Second, 3ds max (and Revit btw, as both share the same code for rendering) still has issues to deal with linear and area lights calculation making them unreliable photometric-wise.

As I write these lines, cove lighting situations cannot be mathematically correct with photometric files in 3ds Max: you will have to do some guess work when working with theses scenarios.

**I know, a 200W lamp does not emit twice as much light than a 100W lamp that was only for keeping the example simple.

To get rid of those edges, you can hide them from the editable mesh panel:

Or better, use a Maxscript tool that will let you hide them all at once.

Click here to download the MaxScript

Usage: Select all your EditableMesh objects and execute the script. The script will only affect selected EditableMesh objects so the selection can contain lights, lines, cameras: they won’t be affected by the script.

The result:

Special Thanks to Chris P. Johnson who helped improving the speed and stability of the script on large models containing several instances.

In Revit you can schedule floor areas and estimate material quantities required for construction.  However, if you want to optimize quantities and placement of building supplies to reduce waste that might not be enough. Pricing estimates might not be accurate either.

To resolve this problem, I wanted to draw each plywood sheet and dry-wall sheet in place so I can get optimal positionning and precise quantities to be ordered. But what if we don’t want to affect the drawing plans? Here is a solution that worked for me, it may work for you as well.

 The concept:

Take advantage of building phases and phase filtering for views.

Example:

1. Add a project Phase at the very end of the list.  Call it “Building Supply Take Off” or something like that:

   

2. Duplicate a floor plan View and assign it to the newly created Phase:

   
   

3. In the newly created view, draw your construction supplies as if you where installing them in reality. Make sure they are also set to the  Phase we created previously. 

   In this case, I inserted 2′ x 8′ panels representing styrofoam insulation. I don’t really have to care about intersections as this is just something used to extract quantities and they will never appear on printed drawings anyways.

   

4. Finally, create a schedule that also filters entities for the “Building Supply Take Off” Phase.

   

The size of the FBX files exported by Revit is influenced by the following aspects:

Model size:

Obviously, the more details in your 3D view, the larger it will be.  There is not much you can do about it besides controlling the way your families are drawn (fine, medium, coarse display settings).

Texture Maps used by the Render Appearances:

All textures used by the Revit materials are embedded in the exported FBX for portability reasons. On one hand, this is useful because you don’t have to bother about file paths issues (”texture not found” errors) but it has a cost in terms of file size. If you don’t render in Revit, you might want to think about editing your materials in a way that textures are not used at all.  This way, the exported FBX file will not contain additionnal image files.

Environment Maps:

Revit defaults to a rendering setting that uses a texture map for clouds.  This texture map on itself weights about 20Mb and cannot be compressed more. Since it is also zipped up with the exported FBX models, you take a 20Mb hit right away. To resolve this issue, switch the render settings of Revit to use a clear sky (no clouds). Doing so will remove the large clouds image file and reduce the size of the exported FBX file.

HDRI and Photography

With today’s typical hardware, it is not possible to capture a lighting design project in a single shot and get it represented accurately on screen “as-is”.  Accurately meaning “how the eye perceived the project at the time the photo was taken”.  Typical digital display devices cannot display the entire range of luminance that a human eye can perceive. Cameras can’t capture that range of luminance at a same time either.  In technical terms, that is the complex (and how interesting) world of Tone Reproduction or Exposure.

For example, your eye adapts rapidly to a variety of contrasts and your brain condenses all this into a unique image, as if you would apply different brightness and contrasts ratios to individual parts of the image.  By opposition, exposure functions of cameras are applied to entire image at once – so the two worlds don’t match very well.

 The future is in what is called “High Dynamic Range” in computer language, where all luminance levels can be captured, stored and displayed into (expensive) devices.

The lecture describes methods to photograph lighting design projects in such a way that results are as close as possible to the human eye perception. Workflows involving image manipulation programs are discussed and demonstrated. 

The attendee learned how to digitally capture the full range of luminance of any given scene (in our case, lighting design projects) with affordable hardware.  He also learned how to manipulate this data with affordable software to create a digital picture that is closer to his perception of the scene.

HDRI and Qualitative Lighting Simulation

HDR Imaging does not only improve our ability to photograph design projects.  It also allows us to improve our efficiency in lighting simulation workflows.  One can use a 3D rendering software to create one image per light source and combine them together in a compositing application.  The advantage of doing this is that the designer can interactively change the intensity of each layer in real time without re-rendering the model each time.

Typical techniques for achieving this workflow are demonstrated as well.

HDRI and Quantitative Lighting Analysis

HDR Imaging also gives us the possibility to perform advanced Daylighting studies of architectural and urban spaces.  We can use this technology to understand glare issues, yearly or monthly cumulative irradiances and more.

Application examples are shown in this lecture.

The measured color palettes can be exported from the Color Munki software as *.CxF files and read back in 3ds Max with the help of a script that I have developped.

The 3ds Max script can be downloaded here.  Simply run it from within 3ds Max using the Maxscript | Run command, browse to a CxF file and drag and drop colors in your materials from the color swatch of your choice.

The exterior twisted steel ribbon representing a race track created a potential of glare for pedestrians and cars passing near by. My mandate was to help the design team understanding if this was a real issue or not.

With the use of computer simulation, several videos where created demonstrating the effect of the reflection of the direct sunlight on the surroundings of the building to identify glare sources. Simulations for the solstice and equinoxes where performed.

Lighting Consultant: One Lux Studio
Computer simulations: Pierre-Felix Breton

I have participated in the process and contributed to the authoring of the following paper: 3ds Max Design Exposure Validation (pdf – 5835Kb) – which describes the process and results.

This project consisted into developping exterior lighting concepts for the tower of a casino in Quebec City.

Color mixing LED light fixtures where selected for their compact size and ease of control for increased flexibility.

Lighting Design: Martin Gagnon
Conceptual Illustrations, Technical Coordination & Diagrams: Pierre-Felix Breton

Planned in 1840 by architect Richard Upjohn and consecrated five years later, the Trinity Church is one of the oldest church in North America.

Now surrounded by the tall buildings of Wall street in New-York (Upjohn would certainly not have made that prediction!), the construction exposes rich details pertaining to the neo-gothic style: carved stone, sculptures, bronze doors etc.

In March 2001, the city was planning a replacement of the street lighting fixtures. This opened the door for a proposal to illuminate the exterior of the building.

To be able to convince the authorities to accept the project, we created highly detailed lighting simulations with a professionnal 3D lighting simulation package.

One of the most difficult task of the project was to model the church accurately: virtually no data was available, except for a set of hand drawn elevations dating from 1930s!

Unfortunately, the project was put on hold by the 9/11 attacks on the WTC where the church was lightly damaged, although some of the lighting concepts where implemented on the front tower later on.

lighting design:

Martin Shaffer and Associates

lighting studies and simulations:

Pierre-Félix Breton

Established on the UNESCO World Heritage site at the foot of Edinburgh’s Royal Mile, the Scottish Parliament has been completed in 2004.

My involvement with the project consisted into working with the lead lighting designers (OVI, Office for Visual Interaction) on the development of a lighting solution that meets television lighting quality, integrates to the unique architectural space and conforms to the global lighting scheme.

The six committee rooms and the debating chamber where lit with a different lighting layout: each space has a distinct configuration of asymmetric vaulted ceilings, suspension cables, trusses and seating layout.

The location and orientation of the luminaires (800+ total) was determined with a combination of high end analysis tools and custom designed 3d modeling tools (more on this subject in the Autodesk Media and Entertainment 3ds max showcase article – pdf).

The lighting of the debating chamber was a challenge on its own due to its asymmetric vaulted ceiling and visible structural elements.

More than 300 fixtures suspended in clusters are aimed in such a way that broadcast lighting conditions are achieved while no occlusion is happening from the architectural elements.

The lighting system of the committee rooms is mounted into “pockets” carved in the vaulted ceiling.

Each luminaire has a precise location and orientation calculated to not be occluded by the edges of the “pockets” and also meet television lighting requirements for intensity and angle.

architect:

Enric Miralles in collaboration with the Edinburgh practice of RMJM

lighting consultants:

Office for Visual Interaction Inc. (OVI) - Jean M. Sundin, Enrique Peiniger

lighting calculations and aiming planning (broadcast lighting):

Pierre-Félix Breton

photos:

Official page of the Scottish Parliament

see also: