Nowhere Man

Your idea was not off-point. Ben's demo does apply to your example of positioning multiple separate images on a billboard that is already drawn in perspective (except that the perspective would be a parallel perspective, not a converging perspective with vanishing points, etc.). The salient point of the demo in that context is that you can not only effectively drag and drop those other images (be they rectangles or stars or whatever) onto the face of the billboard, but having done so, you can also freely rotate them while they are "projected" onto that surface just as easily as you would rotate them when drawn "flat on the page."
Don't let the terminology dissuade you. One big misconception is that "isometric" drawing is just a trivial and limited way to draw "boxy" things. At the opposite extreme is another misconception that it is only appropriate to the engineering department for exploded parts catalogs, and that it is more difficult than it actually is.
The terms themselves explain a lot of it:
Isometric (same measure) drawing is just the most commonly used variant of axonometric (axis-measured) drawing. Its defining characteristic is that all three axes of the measuring system are equally foreshortened, so the same scale (same measure) can be used along all three directions.
Dimetric (two measures) orients the coordinate system in such a way that two of the axes are equally foreshortened. So two measuring scales are used (one ruler for the two equally-foreshortened axes, and another for the third one.)
Trimetric (three measures) orients the coordinate system in such a way that all three axes are foreshortened different amounts.
The key is that in all three cases, the three axes are not arbitrarily foreshortened; they are foreshortened in geometrically-correct proportion to each other. The grids feature takes care of that for you.
The system is actually just as venerable and rich a drawing discipline as "vanishing point" perspective, and just as widely applicable to commercial illustration projects (see my Jan 27 post). It's not trivial, but it's not difficult, either. And you don't have to have a mechanical drafting background to use it.
A few examples already in the Affinity Designer marketing, videos, and Workbook make the point: They range from the mildly "technical" (the building floorplan video) to the completely whimsical (the colorful bird's-eye view fantasy artwork). The stuff Ben has given us a sneak peek at just adds some very useful and powerful automation to the process, which will make such things all the easier and quicker to accomplish.
JET

Regarding callouts:
One of the things I applaud about Affinity is the energy toward keeping the program as elegant as possible. A large part of that is avoiding tool glut (separate dedicated tools for every little specific use), and carefully designing features to serve as many uses as possible.
Especially in a general-purpose illustration program, the proper place to provide for things like callouts (and leader-lines, thrust lines, hidden lines, ghosts, etc.) is a carefully built and thorough Graphic Styles feature.
Affinity still lacks a "path ends" feature. I take that as a hopeful indication that the Team has ideas in mind beyond the mediocre standard-fare arrowheads feature. A well thought out path ends feature can address that and much more.
Also, drawing standards vary widely. Some clients (military branches, for example), specify arrowheads on callouts; others don't. Whenever I have the choice, I do not use arrowheads on callouts because in my experience (both in engineering and technical communications, and behind a parts counter) I find them to create unnecessarily distracting visual "blobs" which actually make it more difficult to find the item looked for.
A well-built graphics styles feature set (which allows multiple strokes and fills, stored Symbols for path ends, positioning of path ends relative to the endpoint of the path, and separate settings for each end) allows an illustrator to build as many style libraries as needed for vertical-application uses.
Canvas, for example, includes style libraries for various established drafting standards. That's fine for its specifically technical marketing focus. But much as I like it, Canvas does suffer from a bit of tool glut.
In a general purpose illustration program, an auto-expanding text object grouped with a styled two segment path can serve as a suitable callout object. Individual users can create special purpose Style libraries for their own purposes or to share.
Connector capability, on the other hand, could be very useful not just for technical drawing and not just for the common decision tree graph or org chart, but for many other things. But even here, I'm not convinced its interface has to follow conventional wisdom as a separate "tool" or a separate kind of object. Why can't connections just be an attribute setting for the end node of any open path? 
JET

I'm hoping that this video just has a low frame rate - otherwise that is one sloooooow app.
 
Also, it appears heavily dependant on 3D at various stages.  We won't be going there.  Designer is primarily intended as an illustration tool.  We have no intention of adding any handling of 3D content or input.  The axonometric features I'm currently working on are just smoke and mirrors on top our existing 2D functionality.  They don't pad out our existing document data in any way to reference or link to some form of plane aware extra information (other than our grid description which is isolated from the actual curves data, shapes, etc).
 
It's all a bit hard to explain.  Basically, if I can add a feature without having to embellish our existing document objects to know about 3D, then no problem.  If a feature requires that objects would need to remember extra information, then we'll have to think very carefully about it.
If it can all be done in the Tool, then that is still ok.  What I want is for someone who doesn't deal with 2.5D to be able to open a document and treat it as 2D, but for people that want to use 2.5D, they can, but the underlying objects are essentially no different - it's down to what tools they use to draw and edit.

Dimensioning is going to be interesting, especially if it needs to conform to the scaling of the grid axis.  As I mentioned before - there is no spoon - your objects/layers don't exist in a plane, they are just drawn and transformed to maintain plane perspective. It's all done at tool time with reference to the active grid plane, and no extra information needs to be persisted with the object.
 
So, this will take some considerable working out (on my part).
 
I'm also not saying when we'd add dimensioning tools.  We have longer term plans, beyond what is on the road map.

You might want to take a look at a tidy little program called DrawPlus for that. Maybe you've heard of it.  
But seriously, the fleshed-out grids feature by itself is going to be light years ahead of the practically non-existent support for axonometric drawing in other mainstream drawing programs. I'm just saying dimension tools will naturally follow as an expectation.
To this day, Illustrator, for one example, still provides no dimensioning tools whatsoever. One has to spend half-again the price of the host program for a third-party plug-in, (for which compatibility chronically breaks when Adobe auto-installs random updates), or resort to cheezy scripts with very limited capability.
So dimension functionality like that of DrawPlus would be another major competitive advantage. (Even completely dumb dimension objects dependent upon manually-entered values would be more than Illustrator provides.)
Though not ideal, it wouldn't break my heart to see dimensioning implemented in stages like the grids feature has been. While waiting for full-functionality is never fun, for anyone who has been paying attention, the staged implementation of Affinity's grids in light of this "sneak peek" should at least be taken as a sign of assurance of Serif's intentions toward continuous improvement. Consider how many not-quite-there Illustrator features added years ago have received no improvements (3D Effect, for example).
Here's a contradiction for you: I wish Serif continued rapid success with the Affinity line, but hope it will forever continue to "act small" in terms of customer communication, reasonable pricing, and improvement development. So far, all that's been very refreshing.
JET

I have another sneak peak for you.
 
This one might be a little hard to follow, but I'll try explain it best as I can.  Something that has always bothered me is when I put a linear or radial gradient fill on something, and then try scaling or shearing the object.  The gradient fill is unstable in that it doesn't track the object transform.  This is because linear and radials fills are positioned relative to two key points, forming a line through which the gradient is rendered.  Elliptical (and bitmap) fills don't suffer from this because they have three key points, forming a rectangle in two axis.
 
So, I decided we need to fix that. See this video: CorrectedFills.mov
 
The top objects have a legacy linear, radial and elliptical gradient fill.  You'll see that when I shear the first two objects, the fill kind of moves around inside the object and doesn't conform to the shear.
The bottom objects have a corrected fill.  When I shear these objects you'll see that the fills continue to adhere to their placement relative to their object.
 
I then show you some new handles that appear in the Fill tool, which show you the "correction" points of the linear and radial fills, connected with dashed lines.  (You'll notice that the elliptical fills appears the same as they need no correction).  These new handles show you when a fill is being corrected, and give you opportunity to place the extra correction points if you so chose.  You can double click the correction point handles to adjust the fill into a conventional linear or radial fill in document space.
 
Why is this important?
 
If I create an asset or a symbol, I can then place it, and transform it, and maintain the visual appearance without the fills distorting.  This is then especially useful for 2.5D drawing - I can use assets and symbols that were designed in 2D, transform them to grid plane (using the new planar tools coming in 1.7 which make use of shear and scale), and they will maintain their fills.
Of course, it is just generally useful, in that it kind of maintains a more WYSIWYG approach to gradient fill placement.
 
 
 
Just, don't ask about conical fills - they are going to take a bit more figuring out.

You have no idea for how long I wanted these sorts of snapping features.
The only app ever offering extensive snapping so far was ViaCAD with the downside that almost everything was line vector based. 
 
1.7 is going to be one awesome release.
 
 

I assume that in your mind, your mean Professional = Corporate? I'm a developer, and I'm on the forum trying to help out. I have the best knowledge of our software, our code, and I can actually fix or implement features. Yet for some reason you would rather speak to a marketing person? Or a member of a support team? Or someone else that can't actually implement the change that you want. That's certainly not the feedback we've received from the majority of our other customers - they really appreciate being able to speak directly to development staff.

At least so far as CS6 ('cause I won't rent business-critical software), Illustrator still can't actually crop a raster image; it can only mask it.
For the benefit of those who may not have "been there," Illustrator trailed versions (i.e., years) behind its historic nemesis, FreeHand, in all these areas:
Editing in Preview Mode. (In other words, simply being able to edit paths with their stroke and fill attributes showing.)
Compound Paths. (Making a path with a hole in it.)
Clipping Paths. (Ex: filling outlined text with a raster image.)
Performing alignment and distribution on Anchor Points (nodes). (Still sub-par compared to FreeHand because Illustrator's insistence on two separate primary selection tools effectively prevents it from "knowing the difference" between a path being selected at the object level, as opposed to merely having all its nodes selected.)
Page 2. Egads! What a concept! The garment-rending, sackcloth-and-ashes outrage from Illustrator devotees (who had practically zero experience with FreeHand or any other drawing program) anytime the need for multiple pages was even mentioned, was just laughable. Why, it was going to be the end of the world; the coming of the apocalypse; illustrators everywhere would be committing hara-kiri!
Predictably, many of those same users now no doubt couldn't live without it. Many probably think Adobe invented the idea. And Illustrator's treatment of it is still cumbersome compared to FreeHand's more straightforward interface.
Basic Math Operators in Value Fields. Another one still inferior to FreeHand's. Illustrator can still only manage a single type of operator in an expression (i.e., multiplication/division or addition/subtraction, but not both).
User-Defined Arrowheads. And man, what a hack job of an interface!
Converging Perspective Grids. Adobe had to acquire FreeHand to copy this one.
That's just off the top of my memory. I could go on.
I've said it here before, and I'll say it as long as it takes: Simple market share no more correlates to functional superiority in drawing software than it does in, say,  motorcycles (my other passion). Illustrator is not the program to emulate. I've seen evidence sufficient to convince me the spunky Affinity Team probably gets that. Some feature requesters...I'm not so sure.
And yeah, time is of the essence in the current window of opportunity opened by Adobe's Customer-alienating licensing change. But compared to the pace of Illustrator's development over decades, development progress of the Affinity line is lightspeed.
JET
 
 
 

Just for accuracy: Node handles do constrain to horizontal, vertical, and other grid angles (not lengths) when pressing Shift in 1.6.1.
No, the full functionality alluded to in the foregoing rants is not there, but it's not as dire as some make out.
I'm a technical illustrator, too, and for my own purposes, I went to the trouble of hacking out a couple of simple Javascripts to allow me to replicate handle lengths and angles between AnchorPoints in Illustrator. So I get the request. But it's not like the full desired functionality is present in even that ostensibly "leading" program.
The Affinity Team is doing great. I, for one, very much appreciate its members making time for direct involvement with Customers in this forum. And while I can be as passionate as anyone about facilitating technical drawing in mainstream general-purpose illustration programs, and though I will also push for "everything I can get" in that regard, I do hope my passion is not thought of as disgruntlement.
Right now, the Affinity line is the most promising platform poised to bring mainstream vector drawing out of its decades of lethargy. And the fact that there will soon be a dedicated Publisher to complete the static graphics triad is huge. Show me another single-source hopeful with all three key elements new from the ground up.
I love asking Illustrator, Canvas, Draw, and even Technical Designer users if they can key a trig function into their pet programs' value fields.

JET

Yes, but merely constraining angles to a desired set of axonometric axes can be accomplished in any program that provides a user-defined constraint angles feature (ex: the Constrain Guides sub-feature of Illustrator Smart Guides, and similar features in CorelDraw and ACD Canvas) without need for a page-spanning grid.
What's always missing in those features, though, is any provision for assigning correctly-proportional ruler scales along the constrain angles. That's why I said in my previous post "If grids are to serve as the rulers...":

I'm glad you're looking into that, because there has to be some provision for specifying properly foreshortened and accurate measures parallel to the three axis directions from any snapable point in the drawing.
One possible treatment might be a radio button set in the Transform palette labeled "Axis Scale" versus "Page Scale." That would at least provide a substitute for what other mainstream drawing programs are missing in their user-defined constrain angles. Moreover, it would enable entering measures in terms of true-measure values.
But even that does not emulate the direct intuitiveness or elegance of even a pre-computer drafting machine. Axonometric drawing, by definition, is all about making correctly-proportioned direct measures along three coordinate system axes (i.e.; each axis must have its own scale factor, and those scale factors must be correctly proportioned to each other), and zeroing those measures from elements of the drawing, not from increments of a grid. And performing such measurements should not require looking away from the drawing to a palette.
That's why I said that if grids are the only provision to serve as those on-page rulers, then the intersection of the grids needs to be able to be instantly and fluidly zeroed to any point wherever a mousedown occurs, just as the scale head of a physical track drafter effectively "moves" to the point of interest in the drawing and allows the illustrator to perform a measure from there without having to look away from the drawing.
The closest emulation I've yet seen of the kind of fluidity I envision is Lazy Nezumi Pro (so close, yet so far). In its isometric rulers preset, three rulers appear at and follow the cursor. Unfortunately, when set to other axonometric angles, those three rulers do not currently display proportional scales; all three still show the same scale. (I anticipate this changing, since LNP's converging perspective rulers do display proportional scales.) Plus, being an application-independent "overlay" seems to limit its functionality for vector drawing because (among other things) it is unaware of the program's zoom. And though tick marks were just recently added to the elliptical rulers (thereby allowing them to serve as elliptical protractors--something essential to serious axonometric drawing), the increments are not yet snapable.
But the interface concept is quite sound and elegant (and not unlike similar cursor-following interfaces of high-end 3D modeling applications). A similar treatment actually built into a 2D drawing program would not have those limitations.
For example, imaging drawing with the Pen Tool in its Straight Line mode:
The Axes feature is turned on. Three light-colored axonometric ruler guides appear, with their origin under the cursor. There are correctly-proportional tick marks along each of the three rulers. This set of guides always follows the cursor during mouseup, while the cursor responds to all the normal snapping candidates.
Upon mousedown, the rulers stay put.  The user drags along one of the axis guides. If he holds a modifier key, the cursor snaps to the tick marks of that axis. If he releases the modifier key, the angle constraint is still active, but the tick mark snapping is not. Either way, though, a distance readout (accurate to 4 decimals, please) continually appears next to the cursor.
That allows the illustrator to draw quickly with reasonable precision without having to look away from his drawing and toward a transform palette. But the transform palette (assuming its Axis Scale checkbox is on) can still be used to manually enter exact length.
Given such an interface, a page-spanning grid would not even be necessary. Sure, it would be useful when one wants to automatically "project" side views drawn "in the flat" onto the axonometric planes, and that's fine. But most of my drawing would be done with the grid display turned off. The whole purpose of axonometric methods is to allow the illustrator to intuitively draw directly into a mechanically-correct 3D orthographic perspective without having to draft side views first.
Oh, I'm all for some fresh innovation rather than just conventional wisdom. I look forward to seeing what you have in mind for the new feature. I just hope it's not too "locked in" to be open to some user feedback in terms of the implementation.
JET