Camera Matching

Topic: Camera Matching
Team Member: Everett
Location: Boiler Island
Challenge: Creating perfectly accurate scenes

For the first post on our brand new dev blog, I thought I’d explain the ins and outs of “camera matching”, a process we use to recreate the environments of Riven. At the time of writing this post, I’m deep in the process of camera matching for Boiler Island, which makes it a great time to feature it here.

Camera matching for our project is the process of taking the original images from Riven and using them to rebuild the scenes exactly as they were. It’s generally a process of trial and error, piecing together information little by little until a scene begins to take shape, matching the original line-for-line.

Ytram cave topology

The Ytram cave walkways and balcony are portrayed here in wireframe. The orange pyramid shapes are cameras matched to images from the original.

The first step in the camera matching for any new scene is always the same: find a predictable object to line up the first shot. You need an object which you know for certain is an exact shape, like a circle or a pentagon, on which to base the perspective and angle of the rest of the scene.

For Boiler Island, that shape was the boiler. Its perfectly cylindrical shape made it a wonderful fit to start matching with. The first shot is very important. You have to be sure that it’s nearly perfect before you move on to matching others. If not, the errors you made in matching the first image will greatly affect your ability to match later images, making the entire process much more of a fumble in the dark, constantly attempting to correct early mistakes. The boiler made the first shot much simpler, by supplying a clear visual representation of the camera’s rotation and location in respect to the shapes of the boiler.

Boiler

Matching the first camera angle with a primitive shape representing the boiler.

Matching an exact camera angle is a tougher prospect than you might think. Each camera basically has 7 relevant variables: X, Y and Z location, X, Y and Z rotation, and the lens angle.

X, Y, and Z locations describe the camera’s exact point-based location in the 3D space. Figuring out the general location is usually the first step to matching a camera. Often when figuring out location, I can use parallel lines in the scene to estimate a general range. For example, in the image above, the boiler is built of circular rows of bricks. By looking at which row is completely parallel with the image itself, I can tell that the camera is probably at a height which is level with that row of bricks. Then I can lock the camera to that specific height and move onto other variables.

Lens angle is the pin that holds it all together. This variable can make or break a camera angle. Basically, lens angle describes the exact section of perspective which is seen by a camera. When you zoom using a camera, lens angle gets very narrow, showing only a tiny piece of a point’s perspective. Zooming out, on the other hand, shows a wider lens angle, framing a much larger portion of the view. Needless to say, getting this value exactly right is imperative, as it directly affects the apparent scale of objects in the camera’s view. If you can manage to estimate the lens angle with accuracy, the rest of the matching is quite simple.

Ytram Cave wireframe

A wireframe pan of the balcony and Ytram cave areas' half-completed guideline meshes.

Once the first shot is lined up reliably, the rest of the process is simply branching out from that information. Then, more cameras are lined up with the basic model. These multiple camera angles then allow more models to be added in which match all of the current camera angles.

Sometimes, angles need to be adjusted to match new models, as well. For example, on Boiler Island, I had most of the boiler area set up and matching well. Then I moved ahead to matching the balcony and cliffs, and realized that none of my camera angles were matched accurately enough for extremely distant features to line up properly. This led to me going back and realigning every camera angle I had set so far, so as to match the new details of the cliff walkways and the balcony.

Ytram Cave walkway

The exit from the Ytram cave to the cliff walkway, matched with a wireframe of our recreation.

Of course, the process of camera matching is only a precursor to the final environment. During the course of matching camera angles with the geometry on the scene, I try to use as little detail as possible to convey the basic lengths and angles necessary to match each new camera angle. I do this both to keep the scene uncluttered, as I do much of my matching work in a wireframe view, but also because what I’m building will not be used in the final game, so dwelling on its details would be a waste of time. The models I create during the camera matching stage are simply to be used as guides when creating the final game assets. The camera matching stage is very freeform and branching, whereas the final modeling stage will likely be much more structured and organized, simply because of the detail involved.

Ytram Cave with the new geometry fading in and out

The newly made Ytram cave walkway is shown here, matched with an image from the original.

The stage of camera matching is certainly where we get our most concentrated exposure to the details of Riven’s original images, exposing some of the mistakes and odd anomalies that dot the images. For example, in an image standing by the boiler’s controls, looking up towards the pump system, you can see towards the lower left of the screen the handle of the paper press, an object that was intended to be completely removed from the game before it was released. (The image’s filename is “287_bislandcrater.1590.png”, for those interested enough to look for it.)

All of this work will culminate to a set of guideline meshes which will span the island and make the final asset creation that much more accurate and streamlined. Camera matching, while tedious and time consuming on its own, stands as an integral part of the process. It allows a level of loyalty and exacting similarity to the original not available by any other means.


49 Responses to “Camera Matching”.

Team members' usernames are in red.
  • Elendil Says:

    So cool. I’m glad to know you’re still working. ;-)

  • John Drake Says:

    Fantastic – what an interesting piece – having played around with Vue, 3DMax and Maya myself (no expert so I am of no practical use to anybody with any of these packages)I am aware of much of what you are saying. The big Riven book gives a fascinating insight into the construction of Riven as well. Stuff like this is not only informative but also helps people to understand the challenges you all face in making this work. A fantastic piece – thank you. Kind regards JD

  • flake100 Says:

    I rememberd that the boiler was ready ?!

  • AHB Says:

    Will you be including the paper press in the new game?

    • Philip Says:

      Since it was taken out of the original game for a good reason, I don’t see us including it in ours.

      • Vincent KREBS Says:

        Of course in the Purist Mode it should not be there, but what if you reconsidered adding it to the enhanced version ? I mean, Cyan chose to remove it because people didn’t identify it as a paper press and they thought it was supposed to actually open or activate something in the game, but everything in Riven is like that… what if they had been wrong in making this decision ? And anyway the press can be seen far away in one of Riven pictures, so isn’t the enhanced version supposed to remove such contradictions. I don’t know, it could be awesome to include it…

  • Victov Says:

    Awesome, it’s good to see that there’s so much activity now. The website’s been dead for a few months and this gives new hope!

  • Victov Says:

    You’re gonna have fun camera-matching these two

    http://victov.com/rivenfail_one.png and
    http://victov.com/rivenfail_two.png

    As you’re getting near the tree it should become bigger right? Well this tree gets smaller when coming near it… Good job Cyan :P

    • John D Says:

      How bizarre!
      You would have thought that once they created the image and rendered it all they would have to do is move the camera and re-render which should automatically take in the new ‘enlarged’ view…

      • Victov Says:

        It’s bizarre indeed, but it was only at my fourth run though the game when I first noticed it, so it’s no big deal :P
        One of the first things I did notice though is that the temple “inside” that island is way to big to fit in, wonder how they’re gonna fix that…

        • John Drake Says:

          Ah, that’s interesting as I have recently been trying to work out the island dimensions from the Riven maps – I think I estimated the temple to be around 22ft long by 13 and a half feet wide (based on the footpath width and using that as a scale- not perfect science I know). Will go back and look at this as I haven’t worked out the island size yet.

          • Victov Says:

            I wonder how you’re going to solve it. Maybe you could make it “fake”. From the outside you see the island as it is in the original Riven, even though the temple wouldn’t fit in, but from the inside you see the temple. I know it’s possible, World of Warcraft did that with all the cities before Cataclysm came out. (version < 3.3.5)

    • XeresRazor Says:

      What you’re actually seeing there is a change in the camera angle, more commonly referred to as Field of View, if you tab back and forth between the images you’ll notice the clouds in the background stretch at the edges, this is because the camera’s zoomed to a different field of view in the second image causing something similar to fisheye lens effect, this is why the tree appears to be a different size. Cyan also had a filter used in the rendering that could generate a barrel lens distortion which will make some images difficult to match up properly.

      • Merijn Says:

        Interesting, XeresRazor. Could you elaborate on the barrel lens distortion filter? For example: where did you find the info Cyan used it, and how does the output of this barrel lens filter differ from setting Field of View in the camera settings?

  • andrew Says:

    Interesting read. Glad to see things are still going – this project has me really excited.

  • TheMagician Says:

    Thank you very much for the hard work you put in Riven’s legacy.

  • Nyreal Says:

    Hey, is the game ready for any beta testing at all yet?

  • Grover Says:

    As a 3D hobbyist, I’m still impressed by the hard work you made so far. Congrats and keep on, guys !

  • Trekluver Says:

    Cool work. Keep it up guys.

  • amfomy Says:

    Thankyou for having a separate dev blog. Good idea – put official news on the front page and leave the nitty gritty to this page. Can’t wait for even more awesome updates!!!

  • Marein Says:

    Great read! :)

  • Ben Says:

    Really cool, I understand, it’s so deductive
    it’s like you’re getting information out of the game you’re not supposed to have, but getting down to the fundamentals of the game, spatially.

    I wonder what else you’ll uncover… especially on Jungle island

  • Vincent KREBS Says:

    However, people keep wondering whether Cyan are willing to team up with you and give you the rights. This is the primary issue right now.

    • Victov Says:

      Interesting, lets hope Cyan is in a good mood… I wonder however, isn’t there an expiry date when it comes to copyrights? Riven’s pretty old…

      • Ahlisendar Says:

        Yeah, but I think it’s really old. For example, most of Disney’s characters still belong to them, even though they’re something like a million years old. And I’m not quite sure, but I think part of that is because Disney bribed the government to extend the length of copyright protection.

        • ironmagma Says:

          Copyright expires 50 years after the death of the author(s).

        • Victov Says:

          I really hope they’re not getting in any trouble. But I honestly don’t think this is going to be a problem. They have contacted Cyan before starting this… right? I mean, it would be unbelievably irritating when Cyan shuts this down right when it’s finally finished…

          • John Drake Says:

            I think that when Cyan sees the amount of work that will have gone into it and the philosophy of the guys behind it they will be quite open and welcoming. This can only be of benefit to them if it is done well – and from the look of what we have seen it will be done extremely well. Cannot wait to see this in the flesh – fantastic job guys…

  • JonBoy Says:

    Thanks for doing this guys, I’m looking forward to many more blogs. Your devotion to this project is awesome!! SO excited to play this when it’s all finished up.

  • goatman82197 Says:

    How will you handle the islands being seen from afar with all the polygons? Could it transform into a prerendered sprite when you leave the island and view it from another island?

    • zib_redlektab Says:

      We’re not entirely sure how it’s going to work, but we definitely aren’t going to have the full islands pre-loaded. Most likely, just a low-poly version of the land mass, with some sprites, or low-poly building models will suffice.

  • Gloix Says:

    Good job! Reverse engineering can be quite hard…

  • Zink120 Says:

    After reading this I just had to make a donation!
    I love what you’re doing and wish you all the best~

  • Aloys Says:

    What about the landscapes? Applying the same degree of precision to those complex shapes can’t be that simple; I assume you must eyeball a lot here. Is that correct?
    Or do you go fully obsessive and try to get it right no matter what?

  • pixelb Says:

    So, what’s the magic lens angle? I’ve been trying to do this with Temple Island and 73.74 degrees comes pretty close, but there’s still a margin of error.

  • BuddhaMaster Says:

    Will the forum be available again?
    Another one, sometime?

  • Nyreal Says:

    I have a question about the beta signup. Is it true that not everybody that signs up will be able to participate in beta testing?

    -Nyreal

  • Gorobay Says:

    Congratulations on getting the original assets from Cyan! Will having the original models make camera matching obsolete?

  • Ywingdriver Says:

    Hey, how is this project coming? I’m a programmer/video editor, I would love to help in any way I can.

  • Ray Says:

    Just outstanding guys !

    Greetings from Holland.

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