Forced Perspective in Small Spaces (like cakeboxes!)

[BG John]

I've been searching for helpful information on using forced perspective, but haven't found a simple idiots guide yet. A quick look through Google and various RMweb topics didn't really help. I'm working on ideas for my Cakebox Challenge entry, and also possibly for my Cameo Competition entry, although this will be much bigger.

 

I understand about tapering everything towards a vanishing point (at least I hope I do!), but is there some clever way to work out how to shorten the length of objects, like buildings, as they go back into the scene? Is it just done by trial and error, or is there a formula related to something? Is there anything else that needs to be considered in the physical design and building? I know colour changes with distance, but I'll worry about that later, if I get that far.

[teaky]

I've been searching for helpful information on using forced perspective, but haven't found a simple idiots guide yet. A quick look through Google and various RMweb topics didn't really help. I'm working on ideas for my Cakebox Challenge entry, and also possibly for my Cameo Competition entry, although this will be much bigger.

 

I understand about tapering everything towards a vanishing point (at least I hope I do!), but is there some clever way to work out how to shorten the length of objects, like buildings, as they go back into the scene? Is it just done by trial and error, or is there a formula related to something? Is there anything else that needs to be considered in the physical design and building? I know colour changes with distance, but I'll worry about that later, if I get that far.

I don't know if it will answer your question John but have you looked at Edwardian's Castle Aching thread?  He has used some perspective modelling on there.

[Norm81]

For the track in my cakebox where I'm doing this, my current plan is a whole bunch of maths in excel with some trial and error.

 

My tunnel walls will be 8cm high 00 brick paper, that I plan to get some clever software to skew/compress one upper corner down to 4cm high and hope all the courses follow throughout the image.

 

I do have two defined points in the scene that are a given scale though, so for every mm you go back into the scene I know how much the scale changes by.

 

Not sure any of that rambling helps really!

[BG John]

I don't know if it will answer your question John but have you looked at Edwardian's Castle Aching thread?  He has used some perspective modelling on there.

How can anyone miss it? It's on a much bigger scale than I'm considering, with quite a gentle change in sizes. My plan is to squeeze 7mm scale railway items into the 8x8x6 box, but make it look as though it shares characteristics with the inside of a famous Police box!

[BG John]

For the track in my cakebox where I'm doing this, my current plan is a whole bunch of maths in excel with some trial and error.

 

My tunnel walls will be 8cm high 00 brick paper, that I plan to get some clever software to skew/compress one upper corner down to 4cm high and hope all the courses follow throughout the image.

 

I do have two defined points in the scene that are a given scale though, so for every mm you go back into the scene I know how much the scale changes by.

 

Not sure any of that rambling helps really!

I know my way around spreadsheets, but don't do complicated maths!

 

I use GIMP to remove perspective from photos, and once added perspective to a roof for a building flat against a backscene, so I know it works in reverse too, but whether it will produce what I want is another matter. I'd rather work in Inkscape though, where I have the option to create Silhouette cutting files if I want.

 

I suspect it will end up being trial and error.

 

I think any comments are useful, to give an idea of what other people have done, or are trying to do.

[peter220950]

Might be worth a trip to Betws y Coed to see the work of the Master, Jack Nelson

 

http://www.lnwrs.org.uk/Modelling/JackNelson.php

 

Particularly Wavertree Station

 

http://letsgoloco.co.uk/tag/jack-nelson-diorama/

 

I think Copenhagen Fields also played with reducing scale, but not sure if this was just buildings getting smaller towards the rear rather than the full tapering forced perspective.

 

Its a fascinating subject, but it's hard enough to manage in one scale never mind different ones at either end of a model!

 

Peter

[BG John]

Thanks Peter. I like Wavertree.

 

I'm thinking of a scene looking down a side street towards a train on the main street. In 7mm narrow gauge, I may not quite get a whole loco and one coach or wagon in, so both ends would be hidden by buildings. If I can add perspective I think it will look better. It's probably worth knocking up a few mock ups to get some practice.

 

What I'm planning for my Cameo layout includes a street scene behind the station, and a bit of perspective there would help too, but may be too difficult as the station is kind of one side of a triangle, with the non railway buildings making up the other two sides. There's a street heading off into the backscene too! It won't be possible to control the viewing angle anywhere near as much as with a cakebox. I want to try to keep down the width of the layout, so I can make it longer but still manageable in one piece. It's based on a prototype station, rather than being something out of my warped imagination, and I want to recreate the scene as best I can, even though it needs some major compression, and moving things around, in places.

[monkeysarefun]

I don't have a particular site to recommend but if you are basing your google search on just model railway topics then try adding diorama and box diorama to the search terms, lots of military and ship modellers use forced perspective in their scenes.

[BG John]

I tried diorama, but it came up with things that didn't seem very useful, like battle scenes, and model car scenes photographed against real backgrounds. I know there must be stuff out there somewhere, and I can pick up a few useful tips from pages like that, but a lot of it is "look at this" type posts, rather than "this is how I did it" ones. I'll do some more searching anyway. I was just hoping to find some railway or town scene specific ideas.

[Compound2632]

The classic forced perspective street from the level crossing on Geoff Williams' Aylesbury is astonishingly shallow when seen in the flesh.

[Edwardian]

How can anyone miss it? It's on a much bigger scale than I'm considering, with quite a gentle change in sizes. My plan is to squeeze 7mm scale railway items into the 8x8x6 box, but make it look as though it shares characteristics with the inside of a famous Police box!

 

Closer to what you're after is the EM layout Aylesbury.

 

The perspective of receding terraced houses is forced much more aggressively than I have.  There was a MRJ article that dealt with how this was achieved.  I have a feeling there was quite a bit of trial and error, rather than maths. 

 

I am, however, considering this same question, as I think I need to go from something like 90% full size for 4mil to 75% in the course of a single building when I come to model the parish church.

 

Thus far, my thought is:

 

(1) Choose the vanishing point and take lines from it out to all 4 corners of the façade.

 

(2) Make a version of the façade at the reduced scale for the rear elevation, and, wherever it fits along the perspective lines is the correct length from the front!

Edited October 18, 2017 by Edwardian

[BG John]

Closer to what you're after is the EM layout Aylesbury.

 

The perspective of receding terraced houses is forced much more aggressively than I have.  There was a MRJ article that dealt with how this was achieved.  I have a feeling there was quite a bit of trial and error, rather than maths. 

 

I am, however, considering this same question, as I think I need to go from something like 90% full size for 4mil to 75% in the course of a single building when I come to model the parish church.

 

Thus far, my thought is:

 

(1) Choose the vanishing point and take lines from it out to all 4 corners of the façade.

 

(2) Make a version of the façade at the reduced scale for the rear elevation, and, wherever it fits along the perspective lines is the correct length from the front!

No 36. I'll read it later. I see the ground slopes upwards too. That should make it interesting in 7mm scale with very limited height!

 

I agree with your two points. The bit I don't know is how you shorten the buildings. Is it a ratio to the average height of each building along the perspective lines? I'm thinking of a terrace, so it will be a straight run of similar buildings, but each building will be different in some way. They'll most likely be rendered, so I don't need to worry about receding mortar lines.

[Compound2632]

I think the Aylesbury street is helped by the fact that as a side-street, there's a restricted angle of view - it's almost always photographed from the level crossing.

[BG John]

My idea is more like looking down a side street from the opposite direction, towards the railway. Except that the railway actually runs in the main street, and there will be buildings behind it. So in 8 inches, I need a decent length of side street, the width of the main street including a train, and some buildings along the back wall. In 7mm scale!

 

The idea is to make static versions of a loco and an item of rolling stock, that I also build as working models for the Cameo layout. I can use test cuts from my Silhouette Portrait for the static versions, assuming I can get my head round doing it. If I fail, both projects will be abandoned! If 7mm scale is too big, I could cut reduced size versions from the same artwork, as I won't need to worry about working bits inside, but would also need different size boiler fittings etc., which would be a pain.

 

The viewing angle will be very tightly controlled, so that shouldn't be a problem. If I can make it work though, as I said earlier, I have a street running into the backscene on the Cameo layout that could be far more challenging.

[Nearholmer]

BGJ

 

I think it's all about 'angle subtended at the eye', so if you have a 1:43 train 150mm from your peephole, what angle does that subtend?

 

Once you know that, back calculate to find the distance you'd be standing from the real thing to subtend the same angle. Then, using the height of a real thing right next to you, you can "back run" the perspective ...... much quicker to resolve by drawing than calculation.

 

All this business of peeping through holes into cake boxes has made me consider entering, with a "what the station master saw" machine.

[BG John]

BGJ

 

I think it's all about 'angle subtended at the eye', so if you have a 1:43 train 150mm from your peephole, what angle does that subtend?

 

Once you know that, back calculate to find the distance you'd be standing from the real thing to subtend the same angle. Then, using the height of a real thing right next to you, you can "back run" the perspective ...... much quicker to resolve by drawing than calculation.

Is that like trial and error disguised as intelligent gobbledegook?

 

All this business of peeping through holes into cake boxes has made me consider entering, with a "what the station master saw" machine.

Presumably you'll need two items that are railway related in each scene. The mind boggles at the possibilities. I wonder if there's a web site devoted to pictures of such shenanigans.

[DCB]

Just a little warning for those not building a cake box diorama. Forced perspective is great if you have a defined viewing point, but it looks mighty weird if you look from anywhere else.   Of course if you are modeling Port Merion...

Not sure colours change with distance in the way many modelers represent, it always seems to darken to me, greens turning black, the opposite to Hornby's infamous Khaki GWR / BR passenger livery.

[BG John]

Just a little warning for those not building a cake box diorama. Forced perspective is great if you have a defined viewing point, but it looks mighty weird if you look from anywhere else.   Of course if you are modeling Port Merion...

Not sure colours change with distance in the way many modelers represent, it always seems to darken to me, greens turning black, the opposite to Hornby's infamous Khaki GWR / BR passenger livery.

The cakebox is an opportunity to try it. As I said earlier, I'd like to try it on my Cameo Competition entry, but it may not work, as the controlled viewing area will be much greater. There will be a street running into the backscene, and my current plan is to obscure most of it with trees, that will have had to grow at a very rapid pace to be big enough! Some forced perspective there may work.

[Edwardian]

I think the Aylesbury street is helped by the fact that as a side-street, there's a restricted angle of view - it's almost always photographed from the level crossing.

 

Agree. 

 

Even the fairly modest forced perspective at Castle Aching is proving difficult to manage given the lack of restriction in view-point. 

 

For a small, proscenium arch-framed, scene, you can get away with being bolder.   A cake box peep-hole is probably ideal.  

 

I suggest that you choose a horizon based on viewing height and base your vanishing point on that.  Then make sure the ground is angled up towards it in conformity with the perspective lines.

 

This is easier to manage with a peep-hole, because the view cannot alter the height at which the scene is viewed; it is always viewed at the height of the hole!

[Nearholmer]

"Is that like trial and error disguised as intelligent gobbledegook?"

 

Well, it was called trigonometry when I was at school, but when it came to exam time my approach was exactly as you describe.

[BG John]

Agree. 

 

Even the fairly modest forced perspective at Castle Aching is proving difficult to manage given the lack of restriction in view-point. 

 

For a small, proscenium arch-framed, scene, you can get away with being bolder.   A cake box peep-hole is probably ideal.  

 

I suggest that you choose a horizon based on viewing height and base your vanishing point on that.  Then make sure the ground is angled up towards it in conformity with the perspective lines.

 

This is easier to manage with a peep-hole, because the view cannot alter the height at which the scene is viewed; it is always viewed at the height of the hole!

I'm planning to build a full size mock up of the Cameo layout so I can experiment with these things. I won't actually make the baseboard for quite some time, as I want to make sure I can scratchbuild the locos and rolling stock first. There's no point going further until I know if I can. I've probably got a year to work on the mock up, and start making the final buildings, before I'm committed. It won't be as complex as Castle Aching though.

 

I wasn't planning to use a peephole in the cakebox, but to have one side fully open, so it's more like a 3D picture.

[BG John]

"Is that like trial and error disguised as intelligent gobbledegook?"

 

Well, it was called trigonometry when I was at school, but when it came to exam time my approach was exactly as you describe.

I scraped through my Maths O Level, and gave up the A Level after the first year, as I hadn't a hope of passing! Since then I've pretty much just done basic maths, and forgotten the rest!

[Nearholmer]

About twelve years ago, we went to two art exhibitions, one in Bilbao, the other in Birmingham, which were all about optical illusions, visual trickery etc. The Bilbao one had large exhibits, many of which one actually entered, and had a bit of the fairground about it, but the things that amazed swmbo and I most were some, apparently very simple, pictures in the Brum one.

 

They appeared to show things like streets, in perfect 3D, and they 'worked' as perspective was shifted over a very wide field ......... conclusion: "Aha, they must be proper 3D models!' ...... but they weren't. The scenes were painted onto shallow, four-sided, flat-topped, pyramids rising towards the viewer, so that, in fact, the "far" end of a receding street was closer to they eye than the "near" end.

 

Jolly clever chaps and chapesses these artists!

[Stubby47]

I take it you've found my 2011 entry... http://www.rmweb.co.uk/community/index.php?/topic/42093-from-a-carriage-window/

 

No clever maths, and I omitted to scale to horizontal dimensions as the buildings move back towards the smaller scale.

 

When seen for real, the view looks distorted, it is important to only allow a monoscopic view (such as with a camera).

 

I had 20" to play with (quiet at the back !)  - doing the same sort of thing in 8" is a far harder challenge.

[BG John]

I take it you've found my 2011 entry... http://www.rmweb.co.uk/community/index.php?/topic/42093-from-a-carriage-window/

 

No clever maths, and I omitted to scale to horizontal dimensions as the buildings move back towards the smaller scale.

 

When seen for real, the view looks distorted, it is important to only allow a monoscopic view (such as with a camera).

 

I had 20" to play with (quiet at the back !)  - doing the same sort of thing in 8" is a far harder challenge.

Yup. It's interesting that it fools the camera, but not the eye, so that's something I'll have to consider. I suppose with 8" rather than 20", it's quality rather than quantity that counts! Although it may be too little, and not work at all.

 

I've just had a sudden thought that I could make my Cameo Layout narrow and deep, so trains run towards the viewer. It would highlight the wacky feature than inspired the plan. A great opportunity for forced perspective, but it might be difficult to build a train than grows as it approaches! Fortunately, the thought is now fading into oblivion!