Saturday, 27 June 2015

Defining Revit Custom Hatch Patterns

Over the years I have defined quite a few Revit custom hatch patterns, and each time I do it I get a headache!  It is usually about 6 months between each attempt at this so I pretty much have to learn it all over again each time.   The format for defining the hatch files (.pat) is so bizarre that it almost defies logic.  Almost, but not quite . . . .

The Autodesk help files have never changed much over the years, and just reading them gets me baffled each time.  So I decided to write my own help file that is actually understandable by human beings, so I can refer to in six months time.  And well, why not put it out there to see if anyone else finds it useful?  Of course there are now lots of  clever little hatch builder programs available, but sometimes you just want something quick and you may not have access rights to download and install that hatch builder.

The example I am showing here is a series of octagons that are quite widely spaced - I originally created it to represent those 'tactile surface indicators' at the base and top of stairs.  The octagons do a pretty good representation of circles on a stair drawing.

The first step is to create a sample of the pattern using lines - say detail lines on a drafting view.  You probably need to show a couple of repeats in each direction - true octagons are simple to create using the 'Polygon Tool' with only two mouse-clicks.



When the octagon is repeated in a Revit pattern, it does not replicate the octagon shape - it actually treats each line as totally separate, and repeats those in two possible directions.  So in order to understand which lines are repeated where, I have colour coded them.  This pattern is based on a 1000 mm square grid with the space between each octagon exactly the same as the octagon width, which means that the orthogonal lines are repeated every 1000mm, exactly offset from each other - a very simple pattern.  The diagonal spacing between octagons is quite different to the octagon width - so the repeats of diagonal lines are much more complex . . . .

Pattern Definition Format

The pattern file is just a text file, saved with a '.pat' extension.
The overall file can have descriptions at the beginning;  it can also have an overall definition of units (important for metric):
;%UNITS=MM

Each pattern definition needs a header prefixed by an *:   a title and description separated by a comma
      *Octagons 1 x spaced,   1000mm spaced and width octagons
It also needs a type definition (Drafting or Model)
      ;%TYPE=MODEL

Each line repeat (in the pattern) is described in one line of text, with comma delimited format.  eg:
0,     1200, 1000,         0,  1000,       400,  -1500
  • Angle  = angle of line from horizontal measured in an anti-clockwise direction
  • Origin x = horizontal distance of start of line from setout point (always orthogonal)
  • Origin y = vertical distance of start of line from setout point (always orthogonal)
  • Shift u (x) = offset distance of start of repeat line measured parallel to start of line
    (in the direction of the line,  ie. to match the angle)
  • Shift v (y) = offset distance of start of repeat line measured perpendicular to start of line
  • Pen down = length of solid line measured in the direction of the line
  • Pen up = length of gap in the line before the next segment of the line starts repeating (measured in the direction of the line);  is always a minus value.
Notes.
  • The Shift values define the repeats in the direction perpendicular to the line.  The Autodesk help files mislead by calling them x and y values - I prefer to think of them as u and v values, which are not necessarily orthogonal.  The Autodesk help files completely omit to mention that they are measured parallel & perpendicular to the line.
  • The Shift values are measured from the start of the line, not from the setout point - another vital piece of information that the Autodesk help files neglect to tell you.
  • The pen down/up values effectively define repeats in the direction of the line.  They are optional.  If they are omitted, you get a continuous line
  • The pen down/up repeat is inconsistent with origin & shift because the coded value of Pen up is the distance from the end of the line to the start of the next - the repeat distance is actually the total of Pen down and (minus) Pen down.

Octagon Pattern Example

The horizontal lines (black)
Angle = 0
Start line x from origin = 1292.9
Start line y from origin = 1000
Shift u of repeat from line start = 0   (ie. it is a direct perpendicular offset)
Shift v of repeat from line start = 1000
Pen down = 414.2    (length of octagon side)
Pen up =   -1585.8   (distance to start of next octagon line from end of first)

0,   1292.9, 1000,         0,          1000,       414.2,  -1585.8


The vertical lines (blue)
90,  1000,    1292.9,     0,          1000,       414.2,  -1585.8

The 45° angle lines (red)
45,  1707.1, 1000,        1414.2, 1414.2,    414.2,  -2414.2

The opposite 45° angle lines (purple)
45,  1000,    1707.1,     1414.2, 1414.2,    414.2,  -2414.2


The -45° angle lines (green)
-45, 1000,   1292.9,      1414.2, 1414.2,    414.2,  -2414.2

The opposite -45° angle lines (orange)
-45, 1707.1, 2000,        1414.2, 1414.2,    414.2,  -2414.2

Pattern File
*Octagons 1 x spaced,
;%TYPE=MODEL
0,   1292.9, 1000,         0,          1000,       414.2,  -1585.8
90,  1000,    1292.9,     0,          1000,       414.2,  -1585.8
45,  1707.1, 1000,        1414.2, 1414.2,    414.2,  -2414.2
45,  1000,    1707.1,     1414.2, 1414.2,    414.2,  -2414.2
-45, 1000,   1292.9,      1414.2, 1414.2,    414.2,  -2414.2
-45, 1707.1, 2000,        1414.2, 1414.2,    414.2,  -2414.2


This needs to be saved as a '.pat' file type before it can be used in Revit.  It can be edited in a simple text editor like 'Notepad'.

Notes:
  • The angle for the last two could be 135° instead of -45°, but the measurement direction would then be in a backward direction, which could be confusing to figure out.
  • If the width and spacing of octagons are not the same, you would need to define two lines at zero and two at 90 degree angles (like the 45 degree line definitions).


I hope this saves me hours of grappling with the file format and help files next time I need to create a quick pattern in Revit.

Thursday, 11 June 2015

Hollow Section Sweep with Adaptive Profiles in Revit

Two years ago I posted a description on how to use adaptive component profiles to create a swept blend form in the Conceptual Massing Environment (CME).  Recently someone asked how to create a hollow steel section sweep in CME.  I realised that I had neglected to mention something about adaptive component profiles that makes them different in yet another way from the traditional family editor:

Traditional Family Editor vs Conceptual Massing Environment - (again)

When you create a profile family in the traditional family editor it is by nature a 2D element (this is dictated by choosing the profile template to create the family).  It also has rules about what it should contain - basically it must be a single closed loop (or chain) of lines/arcs.  When you try to assign it to another family, Revit will pretty soon tell you what is wrong with it if you don't follow the rules:
 In the CME, you have to just create an adaptive component that has some lines in it.  Only you (and your naming convention) know that it will be used as a profile for sweeping or lofting forms.  If you try to create a form using an adaptive profile that has a loop inside a loop, Revit will tell you that it does not like it at all - but absolutely no explanation why:
Select a path and two profiles with nested loops
Extremely unhelpful error message when you try to create a form

How to create a hollow section sweep in the CME

The first step is to create an adaptive component profile that only has a single chain of lines/arcs - this is by nature a flat 3D family.
  • Then the profile can be loaded into another adaptive or mass family (external or in-place) 
  • Host the adaptive profile on the sweep (preferably using points to get maximum control).  Refer to the post on swept blends for more detail.
  • In this example I have only hosted one profile at each end of the sweep, and they are the same size, but you could have different sizes and intermediate profiles to create a lofted form.
  •  Select the path and two profiles
  • Create Form - it should create a solid sweep form providing the path is not too tortuous for Revit to handle.
  • Place two more profiles (smaller this time), preferably hosted on the same points
  • Select the same path plus the two smaller profiles
  •   This time create a void (use the drop down arrow on the Create Form icon)
  • Revit should then carve out the inside of the sweep to create a hollow form
If it does not do so automatically, you may need to use the 'Cut' command to cut the void from the solid form. 

Voila - a hollow steel section sweep.  Both the solid and void forms are hosted on the same sweep path so they will move when it changes.

Friday, 5 June 2015

Tagging what is in a Revit Key Schedule

I have been endlessly frustrated by the fact that you cannot include shared parameters in Key Schedules in Revit.  This means that anything you put into a key schedule can only be used in other schedules - it cannot ever be tagged.
Or so I thought. . . . .

I recently discovered that you can add some system parameters to key schedules, which means that you can use those in schedules and tag them too.  As with most things Revit, the rules for this are weird and (not so) wonderful.


Rule no. 1:   

Shared parameters, have a secret GUID that ensures their uniqueness - you have to add them to schedules by picking them from a list of already available parameters or by adding them from the shared parameter list.  Likewise system parameters in a schedule or key schedule need to be picked from a list of available ones.  It is only too easy to create new parameters by typing in names that seem to have the same name as system parameters - you won't know which is which, as they appear together in lists.  It is only when you start populating them or using them in (key) schedules when you realise your mistake.
For this reason it is really important never to create your own parameters that are the same name as system (or shared) parameters.  With shared parameters it is a little easier as you can go into the definition and check if it was shared or not.

Rule no. 2:  

Once you use a system parameter in one key schedule, it cannot be used in other key schedules of the same category

When you first create a key schedule, you get a list of available fields on the left.  This is a jumble of system parameters and project parameters that you might have created (but not shared parameters).  Because the list is radically different for each category (and varies with subsequent key schedules), I never realised the significance of that list

Rule no. 3:  


Different categories allow different system parameters to be used in key schedules.  There is no rhyme or reason as to which ones will work - you just have to know.  For most categories it is just "Comments".

Categories that do not allow any system parameters in a key schedule include:
  • Grids 
  • Levels

Categories that allow 'Comments' as a system parameter in a key schedule include (NB. I only checked the ones that show up when listing "Architecture" categories):
  • Assemblies
  • Casework
  • Ceilings
  • Columns
  • Curtain Panels
  • Curtain Systems
  • Curtain Wall Mullions
  • Detail Items
  • Electrical Fixtures
  • Entourage
  • Floors
  •      Floor Slab Edges
  • Furniture
  • Furniture Systems
  • Generic Models
  • Lighting Fixtures
  • Mass
  •      Mass subcategories (I only checked Mass Floors)
  • Mechanical Equipment
  • Parking
  • Parts
  • Planting
  • Railings
  •      Handrails
  •      Supports
  •      Top Rails
  • Ramps
  • Roofs
  •      Fascias
  •      Gutters
  •      Roof Soffits
  • Site
  •      Pads
  •      Property line segments
  •      Property Lines
  • Specialty Equipment
  • Stairs
  •      Landings
  •      Runs
  •      Supports
  • Structural Beam Systems
  • StructuralColumns
  • Structural  Connections
  • Structural Foundations
  • Structural Framing
  • Structural Rebar
  • Structural Stiffeners
  • Topography
  • Walls
  •     Wall Sweeps
  • Windows
Categories that allow multiple system parameter in a key schedule include:
  • Areas
         Wow, the programmers really spoiled us by allowing the use of the Name System Parameter - but don't get too excited because this has to be shared across all Area Schemes.  So if you use it for a Rentable Area Key Schedule, it will not be available for a Gross Building Area key schedule
  • Doors
         Out of all the 40+ door system parameters, they gave us those!  How useful.
  • Electrical Equipment
          It looks like the Electrical engineers are being favoured for a change.  But not the mechanical engineers who only get 'Comments' for their equipment.
  • Plumbing Fixtures
  • Rooms
Now this should give us something to work with - although we only get text and material parameters, that should be very useful as those are the ones we most likely want to tag.  I can't imagine wanting to put the finishes into a key schedule as most likely each room could have different finishes - but if you have say a hospital where there are many similar rooms, you might create a key schedule of room types, and those could have preset finishes in a key schedule?
 
The list of categories/system parameters above is not comprehensive - structural and MEP engineers will need to do some inestigation on the categories that do not show up when the list is restricted to "Architecture" categories.

Conclusion

Well, at least we do have some system parameters we can use in Key Schedules.  However the list is very limited, so use them wisely - plan your schedules and tagging needs before you start creating key schedules.  Don't forget that if you have multiple key schedules for a category, the available system parameters can only be used once per category (not once per key schedule).

An example of when you might use one of these precious system parameters could be for rooms or areas - naming the apartment type as say '1 BED' or '2 BED'.  This value could then appear in a schedule, a tag and in properties.  Associated with each apartment type could be all sorts of standards such as minimum areas, rates and parking requirements etc - these would only appear in schedules and properties (and they could be there just for use in calculations).  Things you would not include in the key schedule would be unique information that varies per room or area.

Tuesday, 26 May 2015

Got Your Repeaters in a Twist?


How many times have you tried to create a 'Repeater' from multi-point adaptive components in Revit, only for the result to be a tangled mess, instead of the neat array that you were expecting? 

You may be in luck - there could be a simple solution. . . .

When you select the underlying 'Divided Path' that the repeater is hosted on, it will display the number of nodes (a blue number above the centre of the divided path)
It also shows up in the properties dialog box.  A few other useful properties are also there, including 'Show Node Numbers', which is off by default.  Try ticking the checkbox.
 It will display each node number as well as the total
If you select the other divided path, and do the same thing, you may find that the node numbers go in the opposite direction.  Unfortunately you cannot display both sets of numbers at the same time - so you need to select them individually and remember the direction
If the numbers are in opposite directions, all you need to do is reverse one of them by clicking in the 'Flip Direction' checkbox.
You might be lucky and have the repeater magically untangle itself, but that is unlikely.  More likely it will still be wrong - maybe some missing elements if the node numbers are slightly out of synch.  It is probably better to undo the repeat command before you flip the direction.

Sometimes the hosted adaptive component will disappear when you flip the direction - in which case undo and delete it first - as Revit still thinks it is out there somewhere.

If you have just one hosted adaptive component, you may find that it just gets stretched to another location when the direction is flipped.
In which case you could select the adaptive point at one end, and rehost it to the correct node on the divided path
Once the nodes are matched up you can try the Repeat command again

If that didn't solve the problem, it could be more complicated!  Have a look at some of my other posts on Repeaters - listed on the Repeater Index Page


Saturday, 9 May 2015

Create Form Using Revit Repeater in 2015 R2

When I first started playing around with Repeaters in Revit 2013 a few years back, I was very disappointed to discover that you could not select a Repeater and then create a form.
Well, in version 2015 R2 & 2016 there is a new feature that goes part of the way to solving this:

New feature in 2015 R2 & 2016:  Remove Repeater

Here is how it works . . .
  • Create a new mass family (in-place or external)
  • Set up your rig for the repeater to be hosted on - in this case I have 4 splines (2 pairs, above each other)
  • Select the path elements - in this case the 4 splines
  • Use the 'Divide Path' command
  • Place an adaptive component onto the equivalent points on each divided path - in this case I have a 4 point adaptive component, snapped to the first point on each one
  • Up until today, I would have known that you cannot create a form out of a repeater, so I would have laboriously placed several more adaptive components onto each set of divided path points. For that reason I would keep the number of points to a minimum
  • When you select each of the adaptive components, it will allow you to 'Create Form'
  • Unfortunately with an organic form this is not good enough - it does not follow the splines closely.  You need more more points on the divided path, and more adaptive components - not much fun if you have to manually add them
  • If you are using Revit 2015 R2 or 2016 you can take advantage of the new feature:
  • Get your mass family back to only one adaptive component hosted on the divided paths with lots and lots of points (as in the image above)
  • Select the adaptive component, and Repeat
  • Select the Repeater, and note that the 'Create Form' icon is not available (this is even the case if you individually select just the individual elements of the repeater)
  • Instead there is a new 'Remove Repater' icon - go ahead and try it
  • The repeater is "Dissolved" back to individual adaptive components.  One nice thing is that they remain selected, so you can go straight to 'Create form

  • Now the form follows the splines much more closely
  • Unfortunately you cannot adjust the locations of individual adaptive components on the rig, nor can you adjust the number of adaptive components that make the form - 
  • If you increase the number of points on the divided paths, the form contracts along the rig
 
  • If you decrease the number of points, Revit will give you a warning message that it cannot create the form - not a recommended workflow!

Monday, 27 April 2015

What's New in Revit 2016

This year there is no fanfare about the release of Revit 2016 – not even from Autodesk.  In fact it is almost impossible to find out what is actually new in Revit 2016.  In past years there have been a number of blog posts that gave detailed reviews and lists of new features.  Since I can’t find much out there, I will attempt to fill the gap – although this is not likely to be a comprehensive list.

The process is made more complicated by the interim release of 2015 R2 in October 2014 – this was made available to anyone on subscription.  I imagine that most Revit users are on subscription by now, as it is very difficult to operate otherwise – that means most of you will already be using the features in 2015 R2.

There are also a great number of stability and bug fixes, which are buried away as cryptic lists in release notes – so there may be all kinds of hidden goodies and issues that we don’t know have been sorted out.  Autodesk do themselves a disservice by not making more of the bug-fixes - as they could sometimes make huge differences to workflows if users knew that they could abandon clunky workarounds.

So here is my attempt at a list of what is new in Revit 2016 – based on the Autodesk Revit 2016 Help pages (in italics), with some of my own comments and what I can glean from other blog posts such as Revit OpEd & Revit Rants.   Let me know of anything missing and I will add to it.


Revit 2016 Core Features (Multi-Disciplinary Enhancements)

Revit Speed: There is a general push to increase the speed of Revit, and each release includes some sort of improvement.  However, they are not always easy to document as enhancements, so we, as end users may not be aware of how much underlying work has been done.  However, here is one change that can be described:
Allow Navigation During Redraw: To improve performance when navigating a view, use this new option to interrupt the display of model elements as you move through the model. This feature allows you to navigate the model smoothly and continuously, panning, zooming, and orbiting around the view without waiting for the software to finish drawing elements at each step. This option is enabled by default
 This enhancement only shows its worth on large models, especially with linked files, so don’t expect anything dramatic on a little test project.


Rotate Project North: In addition to rotating model elements, this tool also now rotates view-specific detail elements, including text notes, detail lines, filled regions, revision clouds, and more. The tool is enabled for plan views only.

I have not tested ALL detail elements, but it seems to work as described.  It rotates elevations and sections and their associated annotation ok – so it seems logical that it is only enabled for plan views.

Well, this is a long overdue fix – this could mean that people no longer need to get the project north 100% set up before they start documenting.  I have “Set up project north” as number one on my check-list for a new project, so maybe I can relax that rule now?   
Before Project North rotate - detail elements orthogonal to view
After Project North Rotate by Pick Model Line - detail elements rotated with model
Open sheet view: To quickly open and identify the sheet on which a view is placed, in the Project Browser, right-click the view name, and click Open Sheet. The Open Sheet option is disabled in the context menu when the view is not placed on a sheet, or when the view is a schedule or a legend. (Schedules and legends can be placed on multiple sheets.)

Nice little feature.  Aside from being a time-saver, It will save us from looking at the confusing Sheet properties to see if a view is placed on a sheet (the option is greyed out if view is not on a sheet).

Revisions: The following enhancements are available in the Sheet Issues/Revisions dialog:
The ability to select multiple rows in the dialog makes it easy to delete multiple revisions at once. You can change the starting number for a numeric sequence to zero or any positive number. Alphabetic sequence type is now "alphanumeric," and it can accept any custom sequence of characters. Each value in the sequence can consist of more than one character. Add a prefix and/or suffix to display with values in a sequence



Selection Boxes: you can now quickly isolate selected elements in an 'unobstructed' 3D view -  by clicking on a new feature on the Modify tab on the ribbon.   Great new feature, previously available in a couple of Add-ins. If you select objects in a 3D view, then this feature enables a section box, and crops it around the selected elements;  from any other view type, it takes you to a cropped 3D default view.   It might be annoying if you have a section box already in your 3D view - because it resizes the existing section box that you might have spent hours getting just right

View States: When you save a model and exit Revit, the pan and zoom states for each view are remembered. When you launch Revit and open a view, the view opens to the same pan and zoom states. This feature improves performance when working with complex models.
I am not sure if this might be more annoying than useful – for example when you open a view and find it zoomed into a piece of text, when you need an overview.  we will have to wait and see on this one.


Incidentally, when you change the view scale, it no longer does a 'Zoom to Fit'.  I am not sure when this was changed (2015?) but I am very happy about that.



Multiline text: This is a really nice new parameter type that allows you to force text 'values' onto multiple lines.  I have not really thought this through yet but it seems like it could be a big deal, so it is a mystery why Autodesk have not listed it as a new feature.   It works in printed schedules and tags (if you make them shared parameters).  Refer to Steve Stafford’s blog post for more detail.  In the properties dialog box you need to click to the right side of the text field to get to a separate dialog box.  [Watch out - apparently if you add a multiline text parameter to your shared parameter file it causes problems, so don't try it without reading this post on OpEd.]

Architectural Features 2016


IFC links and rooms: When creating rooms in the host model, you can use many IFC-based elements to define room boundaries.  Autodesk seems to be pushing a lot of new IFC changes – I haven’t had a need for IFC yet, but I’m sure those that do will appreciate any improvements.



Floor Elevations: To improve annotation and scheduling of architectural floors, the following fields are now available: Elevation at Top, Elevation at Top Core (Multi-layered floors), Elevation at Bottom Core (Multi-layered floors), and Elevation at Bottom.  This seems to be only partially working.  It shows Elevation at Top and Bottom, but not the other two, even when you do have multi-layered floors with some plies outside the core.  I have seen it reported that it works for structural floors, but I'm not sure about that.   
Regardless of this, we typically separate floors into structure and finishes (two separate elements) and we never need to check elevation of plies within those - so the working parameters are just fine.

All four parameters appear in schedules but the core ones schedule blank.  Great new feature for quality control of models!
Change the floor offset or level, and the elevation values update
The two important parameters show in schedules (all 4 available)



Place Rooms: Use the Place Rooms Automatically tool to quickly place rooms in all closed and bounded areas on the current level.  Shotgun placement of rooms in every enclosed space! – I cannot see that this would be at all useful as it would take longer to fix everything than to manually place rooms where we actually want them.



Rendering: When rendering a static 3D view, you can now choose between 2 rendering engines: NVIDIA mental ray and Autodesk Raytracer. Raytracer rendering does not support some quality and background options that are available with NVIDIA mental ray.

Note: Autodesk Raytracer is an option for rendering a static image only. Revit continues to use the NVIDIA mental ray engine for functions such as: walkthrough export, FBX export, and previews (material appearance, RPC appearance, light color temperature, and decal).
Right now I don’t know how useful this will be as it is just adding yet another way to do things.  Maybe down the track when it is fully implemented for all situations it might come into its own?  Refer to Dan Stine’s article on AECBytes


Energy Analysis for Autodesk® Revit® : (for Subscription customers)
Tools for Use Conceptual Mass Mode and Use Building Element Mode have been moved from the ribbon to the Energy Settings dialog
-  A new analysis mode, ‘Use Conceptual Masses and Building Elements,’ allows you to perform energy analysis on a model that includes both types of design. This mode can be helpful, for example, when a design is partially detailed and partially conceptual, or when you have modeled conceptual masses to represent additions to an existing building.
-  When you select an analysis mode that includes building elements and then show the energy model, Revit creates 3 views: 3D Energy Model (a 3D view), Analytical Spaces (a schedule), and Analytical Surfaces (a schedule). Use these views to examine the analytical model and make adjustments before running the energy simulation.
-  The Energy Cost Range dashboard provides new analysis tools
in the Results and Compare window to understand the current energy cost of the analyzed building model, and how changes to identified variables can reduce the overall cost.
-  The Potential Energy Savings chart has been moved from the Energy Analysis Results to the Energy Cost Range dashboard. 


Revit Repeaters
There was a new feature "Remove Repeater" introduced in Revit 2015 R2 - so that is now available to you all in v2016.  I believe it should have been called "Dissolve Repeater" see this post for a detailed description

MEP Features 2016

Piping flow units: When you define project units for piping, you can now specify values for Flow in liters per minute (L/min). 

Performance and Volume Only settings for calculations:
To improve performance while working with most duct and pipe systems, a new setting, Performance, has been added to the Calculations drop-down. When this parameter is set to Performance, no system-level calculations are processed. When it is set to None, the system still maintains the logical sections in the system.
To improve performance while working with large Fire Protection, Vent, and Other classification system types, a new setting, Volume Only, has been added to the Calculations drop-down. When the Calculations parameter is set to None, the Volume parameter is not computed. When the Calculations parameter is set to Volume Only, the Volume parameter is calculated. Upgraded projects will have the Calculations parameter set to Volume Only for existing systems in which the Calculations parameter was set to None.


Improved snapping behavior: While working with large system models, you may notice an improvement to snapping behavior. Remote snaps include only the objects in the visible portion of the view, rather than the view extents. In addition, snap filters are now based on the zoom level: when the zoom level is greater, fewer elements are included for remote snapping. When Snap to Remote Objects is disabled, snapping to connectors in linked files is excluded.


MEP fabrication detailing: You can now use LOD 400 content from Autodesk Fabrication products (CADmep, ESTmep, and CAMduct) in Revit to create a more coordinated model. This functionality provides greater certainty for detailers in construction firms that the model accurately reflects the intended installation


Structural Features 2016



Steel profiles: The Structural Section category for structural columns and framing elements provides new dimension parameters for columns and framing elements.
-  Hot Rolled Steel Section Shape Detailing Dimensions
-  Cold-Formed Steel Section Shape Dimensions 


Elevation parameters: To improve annotation and scheduling, the following fields are available:
- Elevation at Top (beams, braces, structural floors, and foundation slabs)
- Elevation at Top Core (multi-layered structural floors, and foundation slabs)
- Elevation at Bottom Core (multi-layered structural floors, and foundation slabs)
- Elevation at Bottom (beams, braces, structural floors, and foundation slabs)
- Reference Level Elevation (beams and braces) 


Release and member forces: To facilitate documentation and connections design and detailing, you can specify member end forces for columns, beams, and braces. This data can be scheduled and added to annotation labels.


Truss chord rotation: When rotating a truss, you can specify whether truss chords rotate with the truss or stay aligned with the truss placement plane.


Local coordinate system: The following Local Coordinate System (LCS) enhancements are available when working with analytical loads
- The LCS widget now displays on curved beams and arc walls.
- When you place hosted loads oriented to the host LCS, the LCS widget displays on the element to show the load direction.
- Loads display properly for curved linear analytical elements oriented to the LCS. 


Area loads: The following enhancements are available when you place area loads.
- You can place hosted area loads on the surface of an arc wall.
- You can apply projected surface loads. Select the Projected Loads parameter to apply correctly scaled loads to a projection angle value. 
 


Rebar display performance: To improve performance so that views open and update faster, Revit regenerates reinforcement only for what is visible on the screen. In addition, if reinforcement appears very small on the screen, it is displayed as simplified lines, regardless of the detail level assigned to the view. 

Rebar placement: The following enhancements are available when placing rebar.
- Rebar Offsets: In the Rebar Constraint dialog, you can now specify rebar constraints to the host and an offset distance from the cover.
- Rebar Constraints dialog: You can now zoom, pan, and adjust your view without closing the dialog.
- Rebar rounding: When specifying reinforcement rounding defaults, you can round to the nearest increment, the next higher increment, or the next lower increment.
- Lock rebar parallel to host face: You can now place rebar parallel to any host face with precision using the Shift key during placement. 


Rebar shapes in paths: To improve reinforcement detailing of concrete, you can assign rebar shapes to the primary and alternating bars in a path reinforcement system.


Rebar scheduling: To improve rebar documentation, you can now include the following parameters and fields in schedules and tags:
- Host Mark displays the name of the structural element hosting the rebar.
- Host Count displays the number of identical structural elements hosting the rebar.
- Quantity by Element displays the calculated value of the total number of rebar per host.


Structural Analysis Toolkit for Revit: The following enhancements are available:

  • Gravity analysis: Apart from static analysis, you can perform gravity analysis. It is the analysis type which by deducing the flow paths of loads lets you determine how vertical loads are transmitted from the top to the foundation of the model.
  • Result Explorer: You can display and explore types of results for gravity analysis.
  • Perform analysis: You can perform a batch of analyses simultaneously. In the Analyze in Cloud dialog, you can specify a type and parameters for several analyses.
  • Website - 3D Structure Viewer: You can display results for static analysis and gravity analysis in 3D Structure Viewer. Moreover, you can display detailed results. Results for members and surfaces are presented in the Local Coordinate System (LCS).
  • Website - 3D Structure Viewer: On mobile devices, you can zoom in/out, pan, and rotate a model using gestures.
  • Website - project page: You can share an analysis with collaborators. Collaborators cannot edit results and cannot download them to the Revit project. They can view analysis results, view a report, and download the Robot model with and without results.
  • Website - dashboard: You can open the Autodesk® 360 Structural Analysis dashboard on the website from Analyze tab.
  • List of messages: You can toggle on and off the list of messages containing information about performed analyses.
  • Revit - Robot Integration: When updating a Revit model with changes in section sizes, the link checks compatibility between the section size from Robot and family types loaded to the Revit project. If it identifies a family type compatible with a Robot section, it updates the Revit model with it.
  • Revit - Robot Integration: You can specify which levels to transfer as story levels and which levels as structure axes to the Robot model.
  • Revit - Robot Integration: During the Revit - Robot link process, orientation of loads is transferred. Loads are presented in the Local Coordinate System or Global Coordinate System, depending on how they are defined in Revit

File Format
Every year we see a new file format for Revit, which is not backward compatible.  Usually we can see a reason for this - some new parameters or a feature with significant changes to how Revit might work.  This year I do not see anything that might justify a file structure change - but I guess there must be something.
Just once I wish we could have a yearly upgrade without a file format change - but of course I still want lots of new features and bug-fixes (like we got with R2 as an interim release).

Revit 2015 R2
A significant number of enhancements were also included as an interim release 2015 R2 - these were made available to subscription members only, in October 2014.  Most of these features are now available to all users of Revit 2016.
I will not list these enhancements here as this post Revit Rants covers pretty much everything, although it does not distinguish between what is exclusive to 2015 R2 vs entirely new in 2016 (listed above).