3D Camera Design Principles

Forum for ARTS/COGS/CSCI 4540 Game Development II, Spring 2017

3D Camera Design Principles

Postby BenChang » Mon Apr 17, 2017 1:21 pm

This is a list of design principles from the book Real-Time Cameras: A Guide for Game Designers and Developers (CRC Press, 2009) by the late Mark Haigh-Hutchinson.

These are all fairly straightforward, but the interesting thing is the way these principles interact in complex situations. Balancing the principle of avoiding unnecessary player manipulation with the principles of avoiding occlusion, keeping the camera in the world, minimizing camera movement and maintaining the reference frame of motion for the player requires giving your camera some intelligence. There are many ways to do this, making the camera's behavior an essential and unique part of your game.

  • Attempt to keep the player character in view (third person cameras). Total occlusion by geometry or other game objects (or alternatively, view frustum culling) of the main player character will disorient and confuse the player, yet surprisingly few games pay attention to this essential point. Note that this does not nec- essarily mean focus on the player character directly, nor does it mean that partial or temporary occlusion is not permissible. The determination of the look-at position of the camera and how this pertains to the player character will be discussed at length later.
  • Prevent the camera passing through (or close to) game objects or physical environmental features. If the near plane of the camera view frustum intersects render geometry, unwanted visualartifacts will be produced. These will certainly detract from the graphical quality of the game, and at best seem very unprofes- sional. This problem is typically easily avoidable; it should be considered as simply unacceptable in modern camera systems. A passable solution to avoid this problem is to apply transpar- ency effects to the geometry in question. By effectively removing the geometry (and indeed actually doing so according to camera proximity), the camera may be allowed to pass through without creating distracting visual artifacts.
  • Do not require the player to manipulate the camera simply to play the game — unless it is a design requirement. For third person presentations, the camera system should be able to choose the most appropriate solution automatically, even in the most complex of situations. It is permissible to allow the player to control the camera when it is absolutely necessary or desirable to do so, but it should certainly not be required. Many games adopt a laissez-faire attitude to camera manipulation, which is unfortunate given its importance. If camera manipulation is allowed (or specified as part of the game design) then care must be taken to ensure the player cannot position the camera outside of the world geometry or into a position occluding the player character. The range of motion and method of manipula- tion must be carefully matched to the game design and technical requirements. An obvious exception to this rule would be first person games, where camera manipulation is an important part of regular game play. Even in this case, there are times where the camera orientation may be automatically adjusted to aid the player without overriding player control. Usually this is a subtle assistance to the player in clearly defined situations. Motion up or down steep inclines may induce some vertical pitching of the camera to assist in aiming or navigation of the world.
  • Allow camera manipulation when possible or dictated by game design requirements. Certain game play situations will disallow camera manipulation, but certainly denying the player this control can often seem restrictive. Naturally, we should strive to present a view that does not require this manipulation, but there are certainly cases where the design would demand the player to examine their environment in detail. It is also true that it can be difficult to judge player intent and camera manip- ulation allows a greater sense of control and determinism for the player. There can be nothing more frustrating to a player than being prevented from seeing the world in a manner rele- vant to their current situation or intended action. The problem, however, is that the camera designer should not abdicate this responsibility as a solution. Additionally, restrictions to camera manipulation after such control has been allowed may be con- fusing and frustrating to the player unless adequately explained.
  • Minimize unintentional camera motion whenever possible. This is especially true of cinematic sequences, but it is true to say that camera motion should be avoided unless it would either result in the camera being left behind by the player character, or the camera interpenetrating the player character. Slight or unintentional camera motion caused by reactions of the player character to environmental factors (or noise from player controller inputs) should be avoided. Similarly, if camera motion is directly linked to that of the player, it often results in an “unnatural” or “stiff” feeling to the camera.
  • Ensure camera motion is smooth. Smooth, frame-coherent motion of the camera is necessary to avoid disorienting or distracting the player. Of course smooth motion is normally achieved via velocity damping, which has the adverse effect of allowing the target object to either accelerate away from the camera or worse, overtake and interpenetrate the camera. Nonetheless, smooth camera motion is of great importance and there are techniques available to assist the camera in cases where the player character is subject to rapid acceleration. Low- pass filters can help smooth out irregularities in movement especially when the camera motion is tied directly to that of the player character, where noise from unwanted player input may cause slight motion.
  • Limit the reorientation speed of the camera. Unless it is under direct player control, rapid or discontinuous reorientation of the camera is disorienting and confusing. Reorientation of the camera causes the entire rendered view of the world to be redrawn; since the direction in which the camera is facing (through the lens as it is often called) determines the part of the world to be drawn. By limiting the velocity of this reorientation, this effect can be minimized. In third person cameras, this may be at the cost of losing sight of the target object for a short period. Instantaneous reorientation is permissible when the cut is made in an obvious fashion such as in combinationwith a repositioning of the camera, but only when the new orientation is retained for a sufficient period to allow the player to understand the new situation. Retention of the player control reference frame (see Chapter 2) can assist in this regard. Still, instant reorientation should occur infrequently, and preferably not in quick succession. Reorientation to a new desired heading should usually prefer the shortest angular direction.
  • Limited roll should be allowed in most regular game cam- eras. Little or no rotation should normally occur around the forward axis of the camera. Again, this is distracting and dis- orienting during regular game play, but within cinematic sequences, it is certainly permissible. Occasionally roll is used as part of an interpolation sequence to change the player’s view of the game world, perhaps as part of a special mode of game play (e.g., climbing a wall and crawling along it). Some games have used this effect to intentionally disorient the player, but it should be used sparingly. Flight simulators and their ilk are an exception to this rule, as they usually present a view of the game world from the point of view of the vehicle. Even so, many people react poorly to extreme roll, so in external vehicle views it may prove wiser to only allow a limited amount of roll to emphasize vehicle banking, etc. There are cases where roll can be used to a limited degree to emphasize differences in game play or to underscore an emotional state of the player character. Clearly, roll is perfectly allowed during cinematic sequences.
  • Do not allow the camera to pass outside the game world. In the vast majority of cases, the camera is required to remain within the visible geometry of the world to prevent the player from seeing the construction of the game environment and thus destroying the illusion of the game play. There are limited cases where it is necessary to position the camera outside of the main game environment but only when care has been taken to hide construction details from the player.
  • Retain the camera position with respect to the player when instantly moving the camera to a new position (third person cameras). In other words, try to retain the same control (and visual) reference frame when repositioning the camera. Many games fail to take this into account, which usually results in player frustration as the character moves in unintended direc- tions when the camera is repositioned. This can often result in the demise of the player character, or possibly cause the player character to cross an area boundary forcing data loading or other delays. Retention of player intent is of paramount impor- tance. As with rapid orientation changes, repositioning of the camera in this way should occur infrequently and in reaction to established game play or player motion requirements. It is also permissible to use this when camera motion would be forced through geometry and/or the camera has lost sight of the player for an extended period (say 2 seconds). This case would be known as a fail-safe.
  • Do not focus directly on the player character when it is moving. This pertains to third person cameras that are often made to look directly at the player character, i.e., the position of the player character does not vary in screen space. While this might seem initially to be correct, and it does present the player char- acter well, it is actually undesirable in many cases. Typically, we need to be looking ahead of the character motion to evaluate the position of the character within the environment and to antici- pate future actions. However, the rules governing the amount of look ahead are complex and will be covered in Chapter 6.
  • Retain control reference frames after rapid or instantaneous camera motion. With third person camera systems using a camera-relative control reference frame, instant or rapid camera motion will potentially disorient the player. This often results in unintended player character motion, possibly resulting in the demise of the player character. At best, this is merely frustrating; at worst, it can induce a desire on the player to throw the controller across the room in annoyance. If the control change occurs at the threshold of a game area, it may in fact cause the player character to cross back into the previous area, possibly forcing a load delay and yet another control reference change.
  • Avoid enclosed spaces with complex geometry (third person cameras). There needs to be sufficient space for the camera to be positioned such that the player character may be viewed in relation to the game play elements within the environment. Small enclosed spaces will require the camera to be moved outside the environment to achieve this. If kept in close proximity to the player character it will likely result in poor framing and frequent loss of line of sight. Environmental construction should take camera framing requirements into consideration from the initial design stages.

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