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Why does CGI look so obvious at home?

Discussion in 'TV Show Forum' started by Bursar, Aug 30, 2003.

  1. Bursar

    Bursar
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    Just watched Two Towers on DVD on my PC, and the CGI scenes are really obvious. I can't remember this being the case at the cinema when I saw it - but that was the best part of a year ago, so maybe I just can't really remember.

    I thought exactly the same about other scenes in a few other films that I've watched both on my PC and on my 32" TV.

    I can't really think of any obvious reason why this should be the case. Does the 20ft wide screen (or however big it is) in the cinema help hide these facts, or is it something else?
     
  2. FoxyMulder

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    Best CGI is when u don't even realise the film you just watched contained CGI, my vote for best CGI in a motion film is Irreversible.
     
  3. Kevo

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    Pirates of the Caribbean has some of the best and cleverest use of CGI I have ever seen in a film.

    The Mask (one of the originals) also uses it to great comic effect.
     
  4. Bursar

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    I wasn't trying to debate good CGI vs bad CGI, just trying to figure out why you can spot it a mile off when watching stuff at home, but it tends to all blend in properly at the cinema.
     
  5. dfield2000

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    I know what you mean about TTT. I though Golum looked totally realistic in the cinema, but I rented it on monday and he didn't look anywhere near as realistic on my Tosh 32".
     
  6. Azrikam

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    Some of it is probably due to psychology. The whole theatre atmosphere tends to be more immersive, so you're more caught up in the film than you would be at home on the couch.

    Also, watching a film in the cinema is usually the first time you're seeing it. Some shoddy CGI stands up on the first viewing, but after you've seen it a couple of times, it loses its charm.
     
  7. Garrett

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    Ditto

    In the cinema it is all new you are taking in the plot, the excitement. Once you have seen it you look beyond that and that is when you start nitpicking the plot and CGI.
     
  8. owenw

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    I'm glad others have noticed this too.

    I remember looking at Gollum and thinking "wow, they've moved up a notch with the the cgi here!" Skin tones and movement were totally convincing in the cinema even on the second viewing.

    Same happened with the Matrix (1st one) The look of the sentinels had me wondering was it GGI or very clever miniatures at some points in the film. The DVD lets you spot the 3D effects a mile off, sadly.

    Is it me or do the 3D shots in recent films look like they are lacking colour or the colour matching is way off compared with the live action?

    Take Matrix: Reloaded.
    OK so while they are in the Matrix everything has a sickly green tint, but in the freeway scene the undercarraige of vehicles etc. looks so more of a dark muddy green colour, and the dark colours / shadows are never dark enough to be more convincing.
    (I realise this may have been done on purpose, like alot of the plot etc. and we won't know until Revolutions so the jury is still out.)

    But I've noticed this in TTT and DareDevil among others.

    Maybe they don't take enough time when compositing the 3D live action together? I'm sure the technology has matured enough to make a decent stab at it by now.

    My 2 cents,
    Owen
     
  9. rhoamish

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    I noticed that the CGI for Gandalf (when fighting the Balrog) was a lot less convincing on DVD than at the cinema.

    However, I was seriously impressed with Gollum on DVD. The skin textures etc. are amazing! I didn't really notice how much effort had gone into him at the cinema.
     
  10. Jsinger

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    The main difference is because DVD isn't film. DVD is much clearer, sharper and unforgiving of less than perfect CGI integration. There is also the issue of most people having the sharpness control on their TV's set too high and the edge enhancement additons often made when mastering DVDs.

    One film that has a lot of breathtaking CGI that you barely notice until you think about how certain camera shots were done... Panic Room.
     
  11. owenw

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    Those are good points Jsinger.

    Panic Room had that very nice "impossible" camera shot coming up the stairs and through the banisters, which was a development of the photo-realistic 3D techniques used for the ultra close-ups used in the apartment gas explosion in Fight Club where they took high-res photos of the correctly lit set from every angle and mapped textures based on these photos onto the 3D model of the set. :)

    The mid-air collision in Fight Club was also mostly 3D but it was very convincing even on DVD.

    I still think that blockbuster movies xould have much more seamless integration (unlerss they are still strying to wow audiences with "cool, 3D FX")

    Owen
     
  12. FWA.jr

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    For me, there was a turning point for Gollum in the extension of his realism. This was basically after he becomes predominantly Smeagol. Nothing technical about it, just the character is more sympathetic, and this happened on both the DVD and in the cinema. Quite an interesting study really. The character never truly became wholesome, until I had a strong emotional connection with him.

    I do know what you mean though. 35mm is much nicer anyway.
     
  13. cosaw

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    I think the size of the cinema screen has a lot to do with it. It's similar to when you look at scenes where backprojection (is it called that?) techniques are done. Anyway what I mean is stuff like two people in a car the scenery is fake it's just a projected video sequence.

    Remember that the field of focus of a persons eye is tunnel like and only around a few feet wide, the rest is peripheral. This is why you need to move your eyes when your driving - even though you know the hazzard is there peripherally you'll need to focus on it to gain more information so you need to look at it directly. With a 32" telly you are looking at almost everthing directly in good focus without having to move your eyes, result: you see the faults. In the cinema most of the scene is in your peripheral vision depending on how close you sit and your eyes may move around to follow the action (usually where the high (beleivable) detail is I would say, faces, people and the like). Your eye is not drawn to the cgi backdrop or both characters at opposite sides of the screen.

    As regards that backprojection technique thingy whatever. Look at T2 some of the best cgi sequences and still totally believable on the telly, however look at some of the in car driving shots and the road scenery is naff/unbeleivable. I don't know what Cameron was playing at. Note: I never saw T2 in the cinema so not sure if it looked as bad but am I'm sure it didn't for the reasons stated above.

    I think it's the same with all artificial things cgi, backprojection, blue screen, green screen.

    A good example: Return of the Jedi special edition ewok/stormtrooper bike sequence in woods used green screen. In cinema still wow after all these years. At home: top notch but somethings not quite right. All effects are also worsened when films are not in there correct aspect ratio usually on a 4:3 telly pan&scan broadcasts, look silly like the Superman films, re-release em in the cinema and let's find out! :)

    cosaw
     
  14. puddleduck

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    I never saw LOTR:TT in the cinema, but I thought the CGI Gollum was about the best CGI I've ever seen - seemed to blend in very well with the background scenery and the character has "weight", whereas a lot of CGI seems to be divorced from the background.
     
  15. owenw

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    I agree Cosaw, I only noticed the back projection was reused on T2 after noticing it in T1 for the future war scenes when the technique was less refined (and the movie was on a tight budget)

    I guess the answer then is for us to go out and buy the biggest projecters/screens we can fit in the front room :D

    I also agree with puddleduck about the Gollum/Smeagol character, considering the character was in the foreground for so much of the film, any flaws would quickly become apparent.
    Obviously character had a lot to do with his depth and believeability, but if the CGI had been lacking we would have spotted it.

    Owen
     
  16. MarkR

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    Only bad CGI bit to raise my eye brow was when the Hobbits were being carried by the tree people, other than that I thought LOTR:2 was a Masterpiece. :)
     
  17. JUS

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    I think it also depends on the system you've got at home. My sister came round to visit yesterday and we watched a few clips on my 8ft screen. She said she noticed so much more on that size of screen..background detail etc. In the cinema the screen is huge but you sit along way back so it's not usually as big as your home projected picture in relation to your seating position....also most of the cinema pictures I've seen recently haven't been in focus so you lose alot of detail.

    Jus.
     
  18. Mr.D

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    Generally I felt that the work in TT was a little bit rushed looking in comparisson to FOTR which was more consistently polished.

    TT felt a little studio bound. Lots of two element comps. (fake backgrounds),
    Golum is pretty outstanding though as is most of the balrog fight .
     
  19. owenw

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    MarkR as someone else pointed out to me:
    Just how DO you make a convincing walking tree? :D
    You can get away with stuff like that in a book easily enough, but on film...?! I bet they wished JRR was around so they could rewrite that bit!

    I get the feeling that they used up most of the effects budget on the Balrog sequence & Gollum/Smeagol animation and had to make do with matte backgrounds for other scenes to cut costs.

    Owen
     
  20. Whiting

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    Yeah, exactly the same for me, Mark.

    I couldn't believe it after the care and attention that had gone into the rest of the CGI in the films that a simple "character superimposed against sky" scene would look so poor. Almost like some of the stuff we saw in the mid-80s, in that respect.

    I did comment at the time that I'd hope they'd tidy it up for the DVD release (but was amazed that no-one else really mentioned it at the time.)
     
  21. Mr.D

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    Well the problem with the tree stuff isn't so much the CG of treebeard which of itself is pretty good and interesting if not entirely realistic : its the compositing in of the live action hobbits and the background plate which just doesn't feel as if its tracked in correctly . I think they rendered treebeard static without a moving 3d camera and faked the motion primarily in 2d to give it the walking motion but the end result is that the background plate just has a guessed move applied to it.

    They would have been better off rendering some place markers in the scene behind treebeard with a proper moving 3d camera. That way you'd have gotten a more coherent movement between the background and foreground plane.

    Also looking at the dvd version the blacks foreground to background don't seem to match very well. Although this might be down to the telecine as I think Weta only work with print densities ( if you work with full negative density you can test the comps a bit more rigorously to make sure they'll hold together if the grader goes nuts on them)

    A bit more dappled light through leaves shadowing on the hobbits would have helped as well.

    I think they ran out of time and just had to get somehting together that worked.
     
  22. owenw

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    Can you explain this process a bit more Mr. D for the uninitiated?
    For example what's a telecine?
    Forgive my ignorance but I thought they did all the compositing, colour matching, gamma correction etc. digitally and then printed out to film?

    It annoys me that they can't get the blacks right as a matter of course, considering how compositing and rotoscoping have become a staple part of movie-making these days.

    Another film of recent times with notably poor compositing has to be Die Another Day which they put down to time constraints aswell.

    Owen
     
  23. Mr.D

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    Well there is also the fact that you can lead a horse to water but can't make it drink especially as its picking up the tab and you have to do what it tells you at the end of the day. Nothing wrong with my compositing on that one!

    There are a couple of different ways to work with film images.
    You can do a process called wedging which is effectively designed to let you work with print densities assumimg you've got a finalised grade. Other way is to work full neg density. ( this means the data behaves like a piece of negative rather than print) Essentially what this means is you are seeing more ( or rather have access to more densities as you'll likely reference them in a print space) than can be represented on a piece of print film struck from neg.

    To cut a long story short if you work full neg density the piece of negative you return to production can be graded as flexibly as any other piece of camera neg ( near enough). If you work print densities the piece of neg you return doesn't have the additional neg information a normal piece of neg would have. So ideally it shouldn't be further pushed around by a grader at the lab ( example if it was graded down a couple of stops the peak whites would collapse to grey: a full density neg will maintain its highlights at peak white for two stops...: likewise to a lesser extent in the blacks if the print density work is graded up there may well be no intensities below the set black point so the blacks will milk out: a piece of neg should be able to disclose more information and still maintain some black levels.)

    Work print and what you see is what you get... work neg and you've got more latitude to play with.

    From a working point of view working full density is a double edged sword: you get a more robust neg but only if you've actually ensured your composite is built with latitude in mind so that if it gets graded at the lab the comp will still hold together ie the blacks match all the way down to the Dmin ( black point on film) and the peak whites ( super whites sometimes called) have enough extension to allow them to hold up beyond the 685 white cut off of print.. It does mean you have to be more rigorous with your comps as you are effectively second guessing what might happen at the lab.

    Telecines these days are pretty sophisticated. They tend to scan the master neg of the film rather than print these days. This gives them effectively a second chance to regrade the entire film ( grading is making colour corrections to the final print off the neg mainly for continuity but also for craetive reasons with regard to colour , brightness contrast). The full neg density as scanned won't fit in a video intensity scale : you get a crushed dark image because of the nonlinear whitepoint mapping of film. The telecine operator has to decide where to lose these intensities to be able to map to video. They might sacrifice a lot of mid to low details if its a very bleached out image. They might sacrifice some of the detail in the peak whites in a very dark scene to retain the black information but they have to lose something somewhere.

    If they've got a shot thats been worked on in print density and they are unaware of that fact they might well decide to place the black point lower than where the operator was actually capable of referencing and they may well pop up a mismatch that wouldn't have been present if the image was viewed on nominally exposed print ( unless the lab grader made a similar boob). If it had been worked on full neg density with a competent compositor they would likely have checked the robustness of the comp if someone decided to lift the blacks.

    Often its not down to the compositor though. The colourspace pipeline is usually set in stone at the effects house that carried out the work ( although if you have the full neg density to start with you can decide to lose some of it in certain instances if you know it won't harmm thew shot.

    There is a shot in The Matrix with Neo doing the building jump that shows a fairly obvious garbage matte surrounding him in the sky. Seeing this at the cinema on film I doubt there would have been anything visible but the telecine has popped this up probably by mapping the whitepoint a little higher than he should have. i know for a fact tha guy who comped this at manex was none the wiser as he was unable to see into this area of the image . On his machine it looked fine.

    So why doesn't everyone work full density? Well a couple of reasons. The files are smaller...less diskspace. If people further down the chain didn't mess with the shots as they had been finalled when they left the effecst house it wouldn't matter if you worked only print densities. If you are comping CG its helps to have the live action plate graded so that the cg is correctly lit for the plate in its finalised graded print form because CG doesn't hold up too well to additional grading at the lab as it normally doesn't have the latitude buitl into it; ( decent compositors will do their best to address this but some effects houses don't expect their compositors to be messing around with CG )

    Of course you can render CG to be robust with regard to film colour space.

    Its quite a young industry you'd be surprised how few standardised ways there are of working.
     
  24. CrispyXUK

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    Hi Keith,

    I assume this a lot like the design/print industry were the various colour spaces ie; rgb/lab/cmyk etc, there are various combinations to make 1 colour. there seem to be a lot of ways to make black(ish) colours, so depending on equipement it is displayed with/on they can vary on display to display?
     
  25. Mr.D

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    Its all about subsets.
    Negative density is your base (largest) reservoir of available densities. Print film ( what you see in the cinema) is a subset of the densities available from the neg. Video is an even smaller subset of available densities from the neg.

    The key thing is you won't see those densities on the neg ( no one looks at negative you can't really) so you have to rationale the fact that you are looking at a print representation of the neg. If you are working print densities what you see is what you get but when its written back to neg it leaves some empty space on the neg : this is what can cause problems if its then dealt with like any other peice of camera neg ( the ones I outline above).

    Historically negative is often over exposed (as much as two stops sometimes) because the nature of negative filmstock is such that if you print it down up to two stops you get a percieved increase in contrast range because of the headroom in the whites ( the blacks get darker but have plenty of detail because they were exposed higher) the whites don't perceivably get darker they appear to stay where they were ( they are getting darker but its just that everything above 685 (out of 1023 code values) will register as white on print.

    The response curve of negative is also designed in a way that exploits this additional headroom ( film is more sensitive in the lower intensity region compared to the bright.... kinda like how the human visual system works.

    Film making is a big long chain and its important to ensure that the stuff you do is robust enough to survive if someone further along the chain is a little bit less careful with it.

    I know and have worked with a lot of the compositors at weta and they are all good guys ( and gals) but when crunch time hits and your left holding the ball through no fault of your own you have to get something together that works rather than having a black hole in the film!

    I've worked on films up to 48hours before it was due to be conformed and printed! I've worked on films where they make you do a hundred versions because they think something isn't blue enough and others where the director is practically begging you to save the shot and you are given a free hand to just get something together. Filmmaking is a lot more panicky chaotic and heath robinson than its portrayed. Its not a really controlled enviroment.
     
  26. CrispyXUK

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    Like the design/print industry then :)
     
  27. owenw

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    My most humble appologies, Mr D., I didn't realise you worked on Die Another Day. No offence was intended. :blush:
    TBH, I wrote that post in haste. The comps weren't at fault but there were a few OTT scenes where the CGI didn't always work convincingly.

    Colour grading used for stylistic reasons in cetain movies impresses me alot (Matrix, Gladiator, X-Men and LOTR spring to mind)

    It sounds like the print/web design industry too (we are always joking that our best work is done just hours before the deadline!)

    It must be frustrating when someone further down the line makes a hash of your work.

    One of the most difficult things in web design is the variation in screen colour/contrast and gamma settings between monitors.
    Is there similar variation between cinema projection systems?

    Owen
     
  28. Mr.D

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    Well there is a lot of variation between prints but cinemas are supposed to adhere to certain standards.

    All monitors vary but its common practice to profile monitors used for graphics work and generate custom LUTs (colour corrections) to sort out any colour or gamma deviations away from ideal aims.

    There are still certain issues with gammut and other display condition factors which mean you can only really tell what something is supposed to look like when its on film or a very impressive grading moniotr with 3d colour Luts ( Look up table).
     

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