THE SMA FORUM ARCHIVE
Posted by Boy Oyng, on 2002-06-07 21:02:13
Forced Perspective Query
Does anyone know of any sources of nuts-and-bolts information about creating forced-perspective sets? Good books? So far, I've not found much useful on the web.
Posted by Strider, on 2002-06-08 05:58:50
Good luck, Bruce!
I have a feling this is the sort of thing you just have to figure out for yourself. Maybe some of the people on the site have experience with it and can share some tips, but basically I think it's a 'do it yourself' sort of thing. Probably the best way to get started is to try to make a small version from cardboard or something, and just keep messing with it until it looks right through a viewfinder. I don't know, but if you're good with computer wireframe, maybe you could try to build a virtual set in forced perspective, and then rotate around to see what it will look like. Probably won't help much in construction though. I'm just trying to get the ball rolling here.
As for building a forced perspective set, I would say start and finish the process in front of a camera in a fixed position. All that matters is how it looks through the viewfinder. I recall reading in an old Starlog or something about the tollbooth sequence from Close Encounters, which was a forced perspective shot. They just had to keep shaving off microscopic increments from those girders until it looked right.
Posted by e_rex, on 2002-06-08 22:47:03
Check out railroad modeling books. You could, for example, build the forground in HO scale and the backround in N scale. That would give a forced perspective making the backround seem much farther away.
Posted by plum73, on 2003-04-30 12:03:32
Hi Bruce -
I was wondering how your Forced Perspective shot turned out and if you had any feed back (as I am trying to set one up at the moment).
I realise that your original query was posted in '02, but for anyone interested in this topic I found quite a good programme - Movie Magic (3): Creating Giants, broadcast on BBC1 08/08/94.
Posted by Boy Oyng, on 2002-06-08 11:08:37
I recall reading in Cinefex once--in an article about either Close Encounters or Greg Jein, can't remember which--that some of the Close Encounters forced-perspective miniature sets were photographable from 2 different angles!
The wireframe idea is a very interesting one. I don't have the software myself. Have to ask around.
I'm afraid I'm looking for a lazyish solution. I'm hoping to avoid eyeballing it and I don't want to attempt to figure out some easy-for-anybody-but-me geometry. I admit I want it handed to me on a silver platter that's bigger in the front than it is in the back. Alas. I'm sure there must be some books or articles out there about this. I mean, there are books on everything.
Here's one link I found that claims there are theatrical set design books that cover the topic:
If you think of more ideas, fire away!
Posted by Jim Aupperle, on 2002-06-08 15:25:39
I don't know of any one place with detailed information on doing forced perspective sets but I can suggest a few places to check out.
"Eugene Lourie, My Work in Films"
Lourie was a production designer, director and creator of visual effects. This book his some great examples of forced perspective sets.
"Film Architecture" edited by Dietrich Neumann
Some chapters touch on forced perspective. Many excellent photos.
has an article on Randy Cook's trick perspective shots in THE GATE
You should be a little more specific when asking about forced perspective sets. I'm assuming you talking about building the set in a diminishing scale as things get further from camera (We did this for the cabin in Evil Dead 2). But you could be talking about a hanging FG miniature or making characters smaller as in DARBY O'GILL AND THE LITTLE PEOPLE. Try to focus in on what you need and it would be easier to answer your question
Posted by StopMoWorks, on 2002-06-08 16:38:00
Boy Oyng wrote:
"I'm afraid I'm looking for a lazyish solution. I'm hoping to avoid eyeballing it and I don't want to attempt to figure out some easy-for-anybody-but-me geometry. I admit I want it handed to me on a silver platter that's bigger in the front than it is in the back."
Many areas of traditional special effects does use "eyeballing". When one sculpts, paints sets, models, etc....all that is kind of eyeballed....it is the Art-Craft part of it! Yourself, experienced stop motion or fx people probably already know this and I am maybe, already "preaching to the choir"!
Although sounds too simple, the tip of .... how the set-up looks in the camera viewfinder....it is a good one. Another tip, go to bookstores and check out drawing books.....usually they go into perspective drawing, which is also about size relationships of elements/things to each other, which contributes to the illusion of depth. Study larger photographs of scenery, cityscapes, etc (from magazines/cheap source)....use tracing paper to outline the shapes in the photos....this will give you flat view of that shape & its size and give you an "eyeballed" understanding of forced perspective principles, then apply it to dimensional miniature sets. The distant elements can even be flat cut-outs. In the Empire Strikes Back....the distant snow walkers were merely cut-outs and they even partially animated them! Incredible with what you can get away with. Again, only what the camera "sees" (the scene being your canvass!)....things can be quick & dirty too.... that is the fun & rewarding part of doing many of traditional (non-'puter stuff)special effects.
Posted by Strider, on 2002-06-08 21:28:04
Here's a thought, based on something Lionel said...
You could try to draw out 'plans' using a perspective grid. Draw a few different ones, at varying angles.... you know, one with a fairly close vanishing point, one a little farther, etc. If your set is something architectural, (like the CE3K tollbooth) then you might even be able to get a pretty good idea of what will work by taping your drawings together like a little model. Then you can use it as a pattern to cut out the pieces.
I think we saw the same article. It must have been in the issue (Cinefex or something) that covered Greg Jein and Close Encounters. I recall, it said that there was a range of about twenty or thirty degrees where it looked right. I have a feeling that, unless you're looking for absolute realism, you can get away with a pretty good degree of 'faking' as well. Meaning that you probably don't have to trim off any precise angles from walls/cieling, etc... there's probably a fairly wide range of acceptable angles.
Bruce, are you already familiar with the basics of perspective drawing? That of course would help immensely. And, as Lionel suggested above, much of your 'set' could probably be a painting, with just the front portion done in 3d.
I just had a thought for a more hands on approach: start by putting up a 'wall' piece in front of a camera. Just a piece of cardboard. Take another piece to serve as a 'cieling' (or roof, depending on whether it's an interior or exterior). Just attatch this with one piece of tape, at one end. Then. looking through the camera, hold it at various angles until it begins to look right. You probably can't actually hold it as you look, but you know... prop it up or something, get someone to help you. It might actually be best to start with just walls, then add top pieces later. Once you've established two of your walls, you can locate the vanishing point. Of course, it may be somewhere in your neighbor's rec room, or in Wichita Falls. Maybe if you're on good terms with your neighbor, you can just go over with a tape measure and tap some nails into his nice tongue-and-groove flooring. Or not.
Posted by Nick H, on 2002-06-09 20:09:17
Looking along a city street with lots of parallel lines going towards the same vanishing point, you don't have much leeway. With natural landscape you can fudge it a lot more. Big trees in the foreground, smaller trees behind, but since trees come in different sizes anyway you're not locked into an exact perspective. Your puppet can walk back to where the trees are relatively smaller, but that's ok, those must be smaller trees. (Try that in a forced perspective corridor with doors getting smaller and the ceiling lower, and the puppet seems to get taller.) An undulating ground helps too - if the buildings in the foreground look big, then the ground dips down out of sight and another hill rises further back with smaller buildings on it, then the brain will get a sense of the distance just from the scale difference. You can't follow the perspective of the road going from one hill to the other because it dips out of sight. So you can't tell it's "wrong". (You could have a small scale car on the road on the distant hill coming towards camera, it dips out of sight in the valley, then a bigger scale car comes up the foreground hill!) A wide angle lens also helps to exaggerate perspective, including the perspective shift as you move the camera. I found I could build a cityscape where the buildings run in rows more or less across the screen, and hide the ground level behind. Then you see another row of building tops coming up behind the first row. If there is a sudden drop in scale btween rows, then you interpret that as meaning there is more distance between those rows - open space, or low buildings maybe, you can't see the ground so there's nothing to contradict that impression. The buildings can be constucted normally, and seen from more than one angle. I avoid making true forced perspective buildings, because you can't do a reverse angle and shoot back the other way without making another set of buildings. And straight buildings are easier to make than forced perspective ones - or deliberately crooked ones too. Of course, a Caligari-esque expressionist set with all weird angles can get away with a lot more that a realistic one.
Posted by StopMoWorks, on 2002-06-09 20:51:44
Nick seems to have a knack of explaining these things in a cogent manner with few words (than me)! There is also the matter of lighting and depth of field considerations. If it's a miniature set representing outdoors...the more distant, usually the more fuzzy (like aerial haze).....there are different ways to do that. Wide angle lens on miniatures is a real neat trick.....much more sense of larger space & depth.....and puppets look way bigger/massive! For movie film cameras, lenses can be pricey. If you shoot with digital-video camcorder some models have built-in lens with very good range....depth of field from about 1/4" from lens to infinity. If you do a Google search, entering "forced perspective", "false perspective", "hanging miniatures" (or other variations).....there may be a few bits of info, but not much. One would then need to acquire books that may cover it.....Raymond Fieldings, "The Technique of Special Effects Cinematorgraphy" is kind of a classic favorite about general special effects. The "old" Cinefex issues every once in awhile went into f. perspective/miniature type shots.
Posted by Boy Oyng, on 2002-06-10 12:09:14
CAUTION! EXCESS VERBIAGE AHEAD.
Preamble: Nick and LIO, I wrote the following before reading your last two posts, so it doesn't address them. But thanks. Helpful as always.
Thanks to all of you for responding. Your suggestions and questions have helped me define the scope of the problem and the issues involved.
Let me respond directly to Jim first. Initially, my hope was that someone would say, "Oh, just check out Chapter 12 in 'The Acme Big Book of Museum Display Construction.' It gives a set of guidelines and drafting instructions." It was probably a naive hope, but I wanted to avoid asking people to explain stuff I'll get into below. I still don't want that.
Thanks to you, I've started to read the Cinefex #30 article (should've thought to check the index myself), and it has a definition of forced perspective that makes me think the term has a more specific meaning than I realized. I assumed "forced perspective" refers to any situation in which one employs different scales within a frame to create an illusion of greater (or lesser) distance between foreground and background elements... much as John suggested in mixing up HO and N scales on a set. In the article, Randall William Cook says that "In forced perspective, something that is actually normal in size--like a man in a suit--is placed farther away from the camera to make it look small. So instead of building a miniature set and magnifying it, you build a huge set and 'mini-fy' it by placing it farther away from the camera." Well, that's NOT what I'm trying to do.
Whatever you call it, here's a sample of the type of problem that got me to posting this: For the middle background of a shot, suppose I want to create a model of the exterior of a small building with a curved archway, but I want to make it look farther away from the camera than it is and larger than it is by compressing its depth. My first goal is to figure out what shapes of foamcore I need to make the model.
Thinking about this in the context of youz guys's suggestions has led me to some conclusions that mostly arise from the basic principle that the horizon should be at eye (lens) level. I'm only just partway through this thinking process. Please let me know if you think any of these are false:
* You angle up the background "ground" so that your horizon meets your lens level. Where you start the angling up isn't all that critical to creating the illusion.
* The more compression of distance you need, the greater the angle of your "ground" relative to the floor you're standing on. A "ground" at 90 degrees would represent 100 percent compression, and one parallel to the real floor is a 0 percent compression. Consequently, if you're trying to make a five foot depth look like a foreground-to-horizon distance, the angle of your "ground" is greater than if you're trying to make a 30 foot depth stand in for the same distance.
*This angle should translate into some kind of factor that you can use to determine the "z" axis dimensions of your model by multiplying it with the structure's nominal dimensions.
* On a model wall running directly in line with the lens-subject axis, the angle of the bottom edge of the wall equals the angle of the "ground." The more off-axis that wall is, the shallower the angle of its bottom edge (assuming that its front wall is intended to appear perpendicular to the lens axis).
* The greater the degree of compression, the less room you have to fudge in terms of camera placement and movement.
* In my particular example, there are two initial, relatively straightforward issues to solve. One is rendering the archway in perspective, the other is determining how big to make the structure relative to the foreground and the deep background.
*Also pertinent are how far from center frame the building is and the angle of its walls relative to the lens-subject axis.
Well, that's where I am so far. It seems to me that if you can nail these things down with some preplanning and precision, then you get the basic skeleton of the set. After that, the "eyeballing" part would come into play much more strongly: to compensate for lens distortions; to finesse atmospheric diffusion; to tweak shadows and lighting; to fix things because they just don't look right; etc. I have to say, it's this "eyeballing" part of making films that gives me the most pleasure, the notion that you can rely upon the audience's imagination to create most of your illusion for you if you just give them the right cues.
So, yeah, model railroading books, books on technical drawing and perspective, and the sudden blossoming of taste and judgment so I can do some miraculous eyeballing.
Because this post is not quite long enough yet, I thought I might share a little tidbit. By coincidence, I just rented the DVD of The Fantastic Worlds of George Pal. In it, he mentions that they knew full well that the moon's floor didn't have cracks in it as he depicted in Destination Moon, but that they put the cracks there because it was such a strong way to use forced perspective and create the illusion of depth of a small set.
Thanks again to all of you. Wish me luck as I continue to work this through.
Posted by Nick H, on 2002-06-19 21:26:47
Say you've got a road going off into the distance...If you're shooting in an aircraft hangar, you'd just make your road on the ground plane completely parallel, going back for 200 feet, and the buildings to the same scale. Since you aren't, you can taper the road. The width of the road at any distance from camera will give you the scale for your buildings. So if it's a foot wide in the foreground where your 1:6 scale puppet is standing, a building that sits where the road is only 6" wide could be built to 1/12th scale. A bit further back and the buildings would be even smaller. You don't need to tilt your groundplane. You could eyeball it through the camera with the road sketched out in marker and a block of wood standing in for the building. Even if you don't have a receding road, a tapered grid heading toward some distant vanishing point could serve as a guide to what scale to use at what distance. This would tell you whether you need to make the building distorted, or whether it looks ok on camera as a straight model. I'd do almost anything to avoid maths, so that's the way I'd approach it. If you're more inclined to tackle it mathematically, go for it.
Posted by Strider, on 2002-06-20 00:06:55
I believe Albrecht Durer spent his entire life trying to come up with exact mathematical formulae to determine how to proportion the 'perfect' human figures. He filled volumes and volumes with oddly-shaped block-men and egg-men and tube-men and suchlike, but never did arrive at that legendary 'perfect formula' that it was thought the ancient Greeks had possessed. Scholars say that, in spite of all this geometrical legerdemain, his most successful figures were done much more intuitively. 'Eyeballing', as it were.
Here's a thought for you... take a piece of cardboard and draw your arch on it, no distortion, and put it up in front of your camera at the angle the wall will be receding. Maybe try zooming in or out to get a different 'aspect ratio'... from wide-angle to telephoto. Watch how the shape of the arch seems to change (if it does). This might help give you an idea of how to tackle it. Or maybe you could find a real arch somewhere and take some pictures from various angles.
My best advice would be, construct your arch inside a framework of straight lines... a rectangular grid. This would be much easier to 'force' into perspective, and once you've got it, you can scribe your arch into it.
Posted by Boy Oyng, on 2002-06-20 01:24:41
Thanks again, guys. As before, your thoughts are clarifying and trigger even more ideas. During the period that the board has been in absentia, I've been researching and thinking about this a lot, and it's turned into an intriguing problem divorced from my actual situation. I think the approaches that you guys have advocated are the ones I'll take, but now, on the side, I feel like I'm on a quest. If something fruitful comes of it, I'll post some more. Right now, I have a Stanford PhD engineer working on the problem! He's given me some trigonometry functions that look cool and are totally befuddling to my mathematically crippled self.
Just for general interest, I found some instructions in a book called "Drawing Scenery for Theater, Film, and Television," by Rich Rose, that includes a useful chapter about creating a perspective drawing from a floor plan of a set, customized for different lenses and aspect ratios. It's a variation of the mechanical perspective instructions found in other perspective books. Doesn't get into forced perspective issues, though.
Mike, the idea of setting up a piece of set and zooming in or out of it would be most helpful if I moved the camera back or forth at the same time, so that the primary subject would stay the same size within the frame. Like that now-overused effect that Hitchcock used for the dizzying interior of the belltower in Vertigo. Otherwise, the arch won't change shape in the frame.
Nick, I like the idea of getting an airplane hanger most of all. It may even be less problematic than my handling trig functions. Sadly, I'm with you on the math avoidance desire.
Posted by Strider, on 2002-06-21 00:55:43
...I also suffer from math anxiety...
Another idea for you:
You could get some long, thin dowels (shishkabob skewers might work) and use bits of plumbers putty (the non-drying kind) to stick them together, and mess around with building frameworks. Once you've got it looking right, you could attatch them more securely and possibly use them as the frame for the building. Or at least to get the general proportions down. I mention plumbers putty for its removable nature... however if you want to use the same dowels to construct your building, it might be better to use something else, 'cause it would leave a really gummy, nasty residue that would make it difficult to stick them together more permanently. Maybe you could instead use corks, and push the skewers through them. Or twist-ties.
Just ruminating here. Things that make you go hmmmmm........
*** Ok, I've thought about it (for about twelve seconds) and I realize that, most likely you wouldn't want to construct a building on a framework made of shishkabob skewers. But once you've got it set up properly, you could hold a piece of foamcore against it and trace the shape for construction by whatever method you prefer.
Posted by johnl, on 2002-06-21 10:22:24
jim riegel talked to us at the aeaf about moving forced perspective where everthing is slid around on stage to keep it in line with the motion control cam... it crazy stuff
Posted by Boy Oyng, on 2002-06-21 10:40:40
John: I didn't know what "aeaf" meant, so I looked it up in Google. I'm guessing you're not referring to Angola Education Assistance Fund, but to the Australian Effects and Animation Festival. Wow, does that look like it would have been great! Did it live up to its advertising?
Mike: Thanks for more suggestions. Since I'm kind of a vegetarian, I'll steer clear of the shish kebabs. I'll use marshmallow skewers... and marshmallows instead of putty. Turn the lights on, leave the room for a while, come back when things are a nice golden brown, and eat my set. Things that make me go "mmmmmm."
Seriously, it's a good idea. I could just use rubber bands to hold the sticks together.
Posted by Strider, on 2002-06-22 04:00:02
I'll bring over some graham crackers, and we'll make s'mores.:9
Posted by gaijinking, on 2002-06-25 13:55:00
When i told Jeremy I wanted a forced perspective hallway macquette for our Shadows and Senses short, i think we were both a little skeptical if we could pull it off. Essentially all we needed was a single plane, single vantage point shot so it was very quick and dirty, but the distortion of the wide angle lens really made it work. Maybe Jeremy can post a response to this... if he can remember since it was fixed so late at night..
Posted by MovieStuff, on 2002-07-04 23:12:11
I think there are two different things being discussed here. One is a perspective shot where miniatures in the foreground are made to line up with items in the distance so as to complete the illusion that the foreground items are part of the background, etc.
Here is a good example I did some time back:
The two cars in the foreground and the gantry are models. The ladder, man, black car and building in the distance are real. The radar truck behind the gantry is also a model.
Here's another view:
The other shot being discussed is a forced perspective shot where the set physically gets smaller the further away it gets from the camera. I believe that this is what our friend is seeking to set up. If so, the method I use is to put a couple of parallel blocks in front of the camera to establish what the "true perspective" of the particular lens is. Then I attached string to the upper corners of the blocks and stretch the string into the distance while viewing through the camera lens. Doing so will let me create the appropriate angle on the strings, bringing them together to a false vanishing point that looks wrong from every angle except through the camera. I attach the strings to a center point and leave the strings up while I build my set, using the strings as a guide for perspective on the roof tops and heights of the various landscape elements.
Oops. I thought I had a photo to illustrate that but, alas, my files are empty. Hmmmm. Well, you get the idea.
Posted by e_rex, on 2002-07-05 15:36:09
Haven't heard from you much lately. Glad to see you're still with us. Hope to see more of your posts soon.
Posted by trikfx, on 2003-04-30 17:24:14
I just noticed this thread, so forgive me if this has been mentioned already.
What if you took an object, let's say, a building, and you wanted to scale it in a forced perspective. You want the building to be halfway to the vanishing point. You have a sense of the size of a building near the vanishing point, and you have a sense of the size nearest to camera, right? Well, what if you made a mock up of the far off building (scaled approximately) and placed it in the shot where it looked right, and then placed a (scaled-up) mock up of the same building close to camera; two points at either end of perspective; then why couldn't you run a string between the corresponding points of both structures, mark the point you want to set the building at, and transfer the lines of the sting to a stand-in blank card. Then you use this card as a rough guide to layout and build the actual building. Use a ratio/proportion equation to calculate height based on the proportional difference between the two original buildings.
I don't know if that came out clear enough, but's thats how I'd do it.
Posted by Boy Oyng, on 2003-04-30 23:52:31
Hi Plum and Ted,
I'd like to see that BBC program. My original question was more about finding methods/tools than solving a problem for any particular shot. I never have found the silver-bullet information source I was hoping to locate, but then I also gave up looking soon after these posts appeared, because I had to stop thinking about it and just get on with it. I vow I'll get back to the search someday, or figure something out on my own.
However, the shot I was most concerned about (at least with regard to perspective) turned out OK--not my proudest moment, but not my most embarrassing, either. The replies here were all very helpful, so I'd study through them carefully before building your set. Note that Moviestuff and Trikfx are among the more knowledgeable participants of this website, and they're suggesting similar approaches (if I'm reading them correctly).
To give you some encouragement, the mind's eye WANTS to make sense of the scene, so it will create perspective where there isn't any as long as there are enough basic clues in place and there aren't major flaws.
For example, if you stick smaller human figures (smaller than your foreground figures, that is) in the background alongside of props and scenery that are appropriately sized for them, it almost doesn't matter where they are relative to the foreground elements or to the camera lens. The mind will make them fit where they "ought" to be. Giveaways would include obvious stuff like putting them in front of things they should be behind, or depth of field. A less obvious giveaway is to have too much detail in the background elements.
Tip: Do put the lens at the same height as your horizon. It doesn't have to stay there, but including that view helps to establish the scene.
Another tip (learned the hard way by looking at the footage of my already-destroyed sets) is to pay careful attention to your sky background. Sizing and positioning clouds to create perspective cues really helps.
Another tip: Do pay attention to atmospheric perspective. I had one scene that took place on a small island, and two scenes that had the same small island visible on the horizon. I built and shot the island scene first, took a still photo of it, then tore down the set. Then I built the set for the scene on the shore that had the island in the distance. I took the photo of the island into Photoshop, partially desaturated it, blurred it slightly, lightened it up a bit, reduced contrast, and gave it a slightly bluish cast. Then I printed it out and mounted it on foamcore. I stuck that on my set's horizon, and it looked pretty far away compared to the foreground stuff. I doubt it would have looked as far away without the manipulations to imitate atmospheric perspective.
Can you describe the problem you're trying to solve? Is it an indoor setting or an outdoor setting? And how large is your "stage" area?