Monday, August 18, 2014


When I was looking for everyday objects to model in point world (for my RTC presentation in Chicago) one of the first pieces of furniture that sprang to mind was the Space chair.  A Fritz Hansen original, much copied, classic use of moulded plastic sheet.

For the longest time I couldn't figure out how to make it.  I kept trying to see the form as a series of profiles hosted on a spline, but that turned out to be really clumsy.

Then one day the penny dropped.  Actually you don't need Point World.  The underlying form is a blend.  It's like one of those thached roofs that are round at both ends with a straight ridge in the middle.

Flip that upside down, at an angle.  Make a similar void, slightler smaller, cut away and you've got it.

Well it needs to be trimmed around the edges of course, but that shouldn't be too hard.  So I started with a profile.

The swept blend was a wonderful thing when it was first released, then a year later it got overshadowed by Point World and I've been neglecting it ever since.  First insight.  You can do a swept blend with a straight line.  Why bother ?  Because it allows you to use loaded profiles, something that ordinary blends don't accommodate (perhaps they should)

Using a straight line as the path for a swept blend gives me lots of control, easy to adjust the length and angle.  The profiles are parametric, easy to adjust their sizes and proportions.  I was using a CAD download from Fritz Hansen as a guide to get the size & shape right.

My first attempt to trim the edges was awful.  Second go was much better, but you can still see sharp edges when you zoom in close.

I decided that I needed a void blend.  Now you can make a void extrusion with a hole in the middle, but that won't work with a blend.  You can only have one closed loop at each end.  No donuts allowed  ... unless you leave a little sliver of a gap somewhere so that actually it's just one loop.

That's what I opted to do.  Not very elegant, but it works.  I leaves you with a spike of plastic sticking out sideways as if the shape had been injection moulded rather than pressed from sheet, but with care you can clip this off so that it's barely noticeable.

Now for the cushions.  I had a quick go at making these in Vanilla also, but it was never going to work, so I'm back in point world after all.  I isolated the cad object for the cushions.  It's a mesh.  Maybe some of you know how to convert this into a solid that will come into Revit and explode nicely.  That would save time, but I've never figured that one out, so I'm going to make if from a series of profiles ... in Point World.

I decided to set up a series of reference planes that slice through a cushion.  They don't actually cut it of course, but I can host splines on these planes and adjust them until they are pretty much sitting on the surface.  A bit tedious, but it was an interesting exercise.

I'm using conventional 2d splines here, the kind that stay resolutely on the reference plane you put them on.  So the only ref points belong to the straight lines that are used to close the loops using 3d snapping.

Use create form on the first 2 or 3 loops. Then progressively add more to create a reasonably convincing replicat of the CAD cushion.

You can easily see where your surface is proud of the original and where it dips below.  Select the nearest spline, look for a node, adjust to your heart's content.

There's always going to be a flat end where your last profile sits, but you can make this very small, or you can just decide that it's not going to show up, especially if the cushions are black, which they often are.

When exporting to cad from a family, your temporary hide/isolate settings are respected, so it's easy to push this out as an SAT solid.  Open this in autocad and you get a chance to round off the sharp edges.

Import SAT back into Revit and explode.  Now it's free-form native geometry and you can apply a material parameter.

The base is pretty straightforward to make so I won't go into much detail.  It helps to set up a ref plane with a parallel section plane when creating the extrusions for the legs and the revolves at the end where they attach to the plastic.

You might think that this results in a heavyweight family, but it's just over 1mb.  I'm not going to spray hundreds of these around anyway. There are a masking regions and symbolic lines to represent the object in plan views.  Interesting to note that the "free form element" for the cushions doesn't trigger a "visibility settings" button on the ribbon.  Fortunately you can turn it off in plan views via the "Visibility/Graphics Overrides" in the properties dialogue.  Another case of inconsistent terminology for Steve Stafford's record book.

I've turned all the 3d geometry off in orthographic views and at coarse detail level.  That should handle most performance issues

For the front & side elevations I used the CAD objects kindly provided by Fritz Hansen.  Just added a masking region.

Hope you found that interesting.  Download the family here

.Space Chair Download

I'm going to finish with a gag reel that illustrates the follies of cleverness.  More failed attempts to create the space chair using Point World gymnastics.

Along the way I developed the most complex trigonometric formula I have ever devised for Revit. (not saying much)  But none of the results lived up to expectations.  What a waste of effort.

Or maybe not.  Sometimes the simple solution will only come to mind after a long & difficult search.

Sunday, August 10, 2014


In my second presentation in Chicago last month I proposed a heirarchy of 3 major types of rig for use in point world: straight line, rectangle & box. 

The series of planters by Frank Lloyd Wright that featured in recent posts were all based on the Straight Line Rig, hosting a series of profiles.  In this post I will use the Box Rig to make families that represent curtains.  The aim is to achieve something approaching the softness and irregularity of real-life drapes.

We start with a rectangle, drawn in plan, using reference lines.  Add equalisation plus parameters for Width and Depth.  Select the rectangle and creat form.  Convert the offset into a Height parameter.  Sometimes it is useful to add formulae that make Height and Depth dependant on the Width, as in the image above.  For the curtains we will keep things simple and type the 3 dimensions in directly.

Make your box 3m high, 1200 wide, and 200 deep.  That will be a reasonable starting point for a curtain that is partly open.  For my RTC presentation, I simply drew 2 splines using Spline through Points with 3d snapping on: one spline along the top face, another along the bottom face.  The points will snap to the edges and acquire NCP parameters (values between 0 & 1 which control their position as the family flexes)  Select both splines and create form.  Add a material parameter.   The result is an undulating surface: moderately successful, but a bit too stiff.

So I decided to add a reference line along the top face, and another along the bottom.  This allows me to vary the depth of the troughs and valleys in a somewhat random manner and create curtains that look more natural, with irregular folds.

Flushed with success, I explored the possibility of even more dramatic ripples with 2 points for each fold in the cloth.  This seemed to work OK but for some reason when you go to a camera view, random lines show up, criss-crossing the scene.  They look worse on screen than in an exported image, but still rather disconcerting.

No worries, I can live with my second version.  Copy this and change the width and depth (wider and more shallow)  Create a new type and apply a new material.  Mine is based on the Bamboo that comes with Revit, but enlarging the scale and fading the image so that it simulates a sun filter material.  Now we have 2 layers of drapes. 

Check out a plan view.  You get some very interesting shapes, but not what you would want in a set of drawings. 

Building plans are stylised.  Sometimes we forget that, but it's the main reason for the "symbolic" capabilities of Family Editor.  Hide the solid geometry of your door panel, and add symbolic representation of a "door swing".  Sadly this feature is missing from Point World.

We had some very interesting discussions in one of Paul Aubin's sessions at RTC, effectively a dialogue with Autodesk at a fairly senior level.  One of the ideas that came up was to have a new family template, possibly called "Generic Model CME", which behaves like a standard Generic Model family, but uses Point World techniques for making geometry.  It would have the visibility controls shown above, plus Symbolic Lines, Masking Regions & Detail Items. 

You would be able to go to family categories and swap to just about any category you wanted, including plumbing fixtures.  It would not be based on adpative points, so the family would respond to the "Level" and "Offset" instance parameters just like a normal Generic Model and you could schedule the components by level.  Even better, you would be able to nest this type of family within a hosted template.  So you could have a wall mounted light fitting based on Point World geometry.  We don't know yet whether this is a realistic request.  Perhaps the coding would just get too messy.  But it would be a wonderful thing if the factory discovered that it was able to grant us this wish.

In the meantime we will resort to work arounds.  Here is one.  New family, Generic Model.  In the plan view, set up reference planes, parameters and symbolic lines as shown below.  Nest this family into another Generic Model.  Create an array, link parameters and "hey presto" we have symbolic representation of a curtain inside a Generic Model family (not a detail item) 

This is good news because we can nest a GM into Point World.  So load it into your curtain, place it ina plan view, lock the bottom left corner to the same corner of the box.  Now you can link up the parameters.  You'll need to set up a formula in the curtain family to generate an "X" value based on Width and No of folds.  If you do this correctly, you will have a symbolic representation of a curtain that flexes correctly and only shows up in plan views.

How do we hide the 3d geometry in plan ?  I made a new sub-category called "adaptive 3d"  (my curtain family was made from the Generic Model Adaptive template.  In many ways it would have been better to start from "Conceptual Mass")  So assign the curtain geometry to that new sub-category, and in the project you can turn the sub-category off in plan views.  If you use a view template, it's not too painful.

Why do I say that the "Mass" template would be better than "Adaptive" for this kind of family ?  Well Adaptive Components don't respond to Levels & Offsets the way that other families do.  They're not meant to.  Adaptives are supposed to attach themselves to points within the project and adapt their size and shape accordingly.  They don't have an origin in the same way as normal families.  They are Shape Shifters.  They don't belong to any particular level.  They define themselves in relation to other objects, not to some absolute datum.  So if you want to control the position of your family by selecting a level and typing in an offset, Adpative Components will disappoint you. They also have a disconcerting tendency to flip upside down when mirrored.

So my freebie is slightly different from the above story.  It's a mass family, the symbolic "worm" is centred about the origin (which usually is a more stable way to make families) and the subcategory for turning things off is called "_Hide in Plan"

Check it out for yourself at this link.

Mass Curtains.rfa

Tuesday, August 5, 2014



I have a passion for buildings.  It began when I convinced myself as a teenager that I wanted to become an architect. I was impressed by the way that many architects wrote about their work, how they seemed to believe that they were on a mission to change the world.  And of course, I loved to draw.

Disillusion set in early and by the time I had finished my first degree I had decided that I didn't want to be an architect after all.  I convinced myself that there were more direct ways to change the world than some office job.

Plunging into manual labour on building sites I discovered a fascination for building processes that college courses had failed to ignite.  I decided to train as a bricklayer and spent the rest of my twenties plying this trade in the North of England and scribbling construction details into my sketch books.

At the age of 30 my passion took me to Africa on a wild adventure, teaching building at an experimental school.

I was disappointed by the textbooks and decided to write my own over the course of a long vacation.  It was just a jumble of ideas arranged on a handful of pages, but it was picked up by my employers and eventually got me a job in the Curriculum Development Unit.

We wrote textbooks, ran courses for teachers, devised schemes for distributing tools to schools, wrote a new syllabus, set exam papers ... it was a wonderful period, filled with belief in the future of the newly independent state of Zimbabwe.  Building was a subject on the secondary school curriculum, alongside English, Mathematics, Geography etc.  We felt that a course called "Building Studies" should not be a vocational option for the "less gifted" but rather a proud subject in its own right.  It seemed to be an ideal vehicle for integrating the other subjects and demonstrating their relevance to real life situations.

This period of my life culminated with two years in the Faculty of Education at the University, devising and teaching a new course for Building Teachers.  This was an opportunity to bring together the various strands of my life so far: Drawing, Architecture, Bricklaying, Education ... In my imagination I thought that I had found my vocation, but it was not to be.  It turned out that I was an expendable tool in someone else's grand plan.

And so I found myself forced to reconsider and opted to give architecture another shot, almost 16 years after I had finished my first degree.  This lead to another voyage of discovery, another set of challenges, another perspective on the world of buiidlings.  I worked in an office for 2 years, went back to University for 2 years, joined another office and finally took my professional practice exam.

Another 2 decades have passed.  One in Africa, and one in the Middle East.  All along a project has been brewing at the back of my mind.  I wanted to recapture the excitement of the unfinished series of textbooks I worked on in the early 80s, but also to add insights from my work as an architect and from my travels to different regions of the world with their different building traditions.

At some point I fixed upon a working title: "The Way We Build".  It is a ridiculously ambitious concept.  Take history of architecture, construction technology and theory of design: mix them all up together with a survey of vernacular building forms and reflect upon ten thousand years of urban settlement along the way.

For almost 20 years I have been assembling a database and creating my own analytical drawings whenever time permits.  Six or seven years ago, I realised that BIM software (Revit in my case) is an ideal vehicle for this kind of research.  My database is littered with half-finished Revit models, many of which have found their way on to the pages of this blog.

Two buildings have emerged from my recent tour of US/UK.  First is Robie House: the apogee of Frank Lincoln Wright's prairie houses phase.

Second is the De La Warr Pavilion: Erich Mendelsohn's contribution to the sudden flowering of Modernism in 1930s Britain.

Both are works in progress.  As always there is an element of guesswork when it comes to reconstructing the dimensions, but that's part of the fascination.

There remain many small anomalies to be resolved, structural puzzles to be agonized over.

There are always details that you notice in passing, but only assume significance as the model develops:  places where Frank opens up a balcony or a roof to let a shaft of light pass through for example.  Are these really justified in practical terms, or are they just architect's games ?  Borderline perhaps.

I decided to use feet and inches for Robie.  Takes me back to my school days, before England went metric.  That in itself has been an interesting challenge.  Frank definitely used a 4' module in the planning, so it seemed more faithful to bite this particular bullet.

I find myself reacting to the gushing use of "masterpiece" and "genius" in what has turned into a FLW tourist industry.  Certainly he was a remarkable and most prolific designer, but what does Robie House really mean to us today ?  It's a huge house with servants quarters, expensive to heat and maintain.  What does this tell us about the social divisions, even in America, just before the First World War ?  It's just a 3 bedroomed house for a successful young businessman, but it's built like an ocean liner.

In amongst the drawings I found on the internet were some from a 1960s "Historic American Buildings Survey".  One in particular stood out as going beyond a dry record of dimensions and attempting to add some analysis under a series of headings: sun control, ventilation, heating, lighting, insects.  Date: 1967, Drawn by: Mary Reyner Banham.

2 years later, I enrolled at the Bartlett (then called the School of Environmental Studies) and sat in awe during lectures by her husband, Peter Reyner Banham, a big man with a big beard and big ideas about the history of the Modern Movement in Architecture.

There are fascinating environmental systems in Robie house.  Wright worked very hard to integrate the heating and lighting into the architectural form.  One example is the way that radiators are tucked under window sills behind slatted timber grilles.  I didn't study these carefully enough as the tour guide whisked us around the interior, but it seems clear that there is an outer frame with an inner screen that either hinges or lifts out to give access.

Wright's timber detailing is generally lauded for being simple and direct, a brave departure from the heavy ornamentalism of the time.  Maybe so, but it still seems rather fussy and overhearing to a modern eye, quite different from the stripped minimalism of the De La Warr Pavilion.

The pavilion is named after "Buck" de la Warr, the 9th Earl, who was the first hereditary peer to join the parliamentary Labour Party.  He was descended from the 3rd Baron, Thomas West, who put down an indian "rebellion" in Virginia in 1610 and after whom the Delaware River is named.  Presumably the spelling was changed to match the pronunciation.

Buck was Mayor of Bexhill in 1933 and instrumental in promoting the architectural competition that was won by the recently formed partnership of Mendelsohn & Chermayeff.  Chermayeff was Russian by descent, but grew up in England.  Mendelsohn was on of many emigre intellectuals who arrived in England during the 1930s.

Fascinating history, and much more could be said, but not today.  The pavilion comprised large multi-purpose auditorium and a long strip of secondary functions.  Today this houses gallery spaces and a restaurant.  Originally there was a restaurant, bar, library and conference room.

The pavilion has been through ups and downs over the years but with remarkable continuity of function.  Today it has been splendidly restored, and hosts a continuous stream of exhibitions and performances.  Look it up on the web.

So that's a peek into my latest explorations for The Way We Build project.  I'm looking at a couple of possibilities for collaboration.  Hope that pans out.  It would be great if more universities caught on to this kind of approach, using BIM to research our Heritage, in the spirit of Peter & Mary Banham ... now wouldn't that be wonderful ?