In this log I show how the prototypes were developed for limb behaviour and structure, these began with a standard arm composed of an upper and lower arm as well as a hand. Then a tentacle type arm was developed as well as a torso to test for stability and to get a general feel for the manner of limb movement. A case study was then conducted to examine how other games handle limb movement.
Two limbs and two methods of control
Two different limb types were developed, each of which had two different methods of control. One was a limb that functions by adding forces to the upper limb to close and rotate with limitations. This would be a traditional way to manipulate an upper human arm.
So in this case the player moves the upper arm towards the cardinal directions. The upper arm pivots from the connecting body, shown above the connected body is a cube. The lower arm and hand are not affected by the controls and aimlessly flop around, this does produce the desired comical effect however. The results of this intial test, while promising does not grant accurate control of the limb. At best this maybe used as a way to swipe at objects, then it could be used for a different limb type.
The second limb was made without distinct joints, eventually becoming a tentacle. It is controlled by manipulating the tip of the tentacle, the rest of the tentacle is linked between the body and this tip.
These first two limb prototypes are controlled by keybaord which is not the targetted controlling device. In that case I believe enabling a controller device would be the next step.
The first iteration of these limbs were attached to a static box, which the limb is attached to. This was found to cause some issues with the joints in each limb. As such a torso was developed to attach the limbs to.
Torso to tie it together
This torso showed how the limbs would interact with each other and the environment. An interesting result was that the limbs produced enough force to pull the torso away and onto the floor.
This is undesirable so a constant upward force was applied to the torso to keep an upright stance. With the addition of this torso came legs too, next steps would be to add controls for the legs too.
During the implementation of the legs it was found that the legs would simply be dragged along the floor and not have any affect on the rest of the body. A simple solution in Octodad was to increase the mass of the feet to ground the Octodad feet, the same has been done here and there is evidently more stability. However this will be temporary as the legs are not affected by inputs.
The next step would be to implement an input system for controller devices, specifically the PS4 controller or Xbox controllers. This would affect the way a player would interact with the limbs, so the method of input would need to be considred and reasearched in other games.
Limb control case study
This case study will be focused on how input is approached in both Human: Fall Flat (2016) and Octodad: Dadliest Catch (2010). I will specifcally look at how:
- button mapping for controllers
- what character actions are possible to accomplish
- how the player character interacts with the rest of the game world
Human: Fall flat limbs
Human: fall flat’s controller layout is quite simple. One thumbstick is used to move the player character, the other controls the camera view. The two shoulder/trigger buttons are used for manipulating the hands of the player avatar. One button makes the avatar jump and another is ‘Play dead’ where the avatar enters a rag doll mode where the avatar’s body goes limp and cannot move.
This layout is quite intuitve as there are dedicated buttons for both limbs, these being the left trigger/shoulder button that controls the left hand and the right trigger/shoulder button that controls the right hand. The other input mappings follow traditional controller button mappings (left thumbstick for moving, right thumbstick for looking and the X or A button for jumping). The actions these buttons can achieve are fairly conventional.
The thumbstick for movement simply moves the avatar in the desired direction, accompanied by animation of the avatar legs (used to comical effect). The left and right trigger buttons move the hands outwards and are directed along the direction of the camera view, then if the camera is looking up the hands would be reaching upwards too.
Pressing and holding the left trigger Pressing and holding right trigger
These hands interact with the rest of the environment in specific ways. Once hands are extended, any surface that the hands come in contact with becomes stuck to the hand. This has different effects depending on the surface.
If it is a static part of the environment, the avatars hands are anchored to this surface and the avatar cannot be separated from it unless the player stops pressing the corresponding trigger buttons. This allows players to manoeuvre the avatar over ledges by sticking hands onto ledges and then moving the camera view downwards, which also rotates the arms and places the avatar over the ledge. For non-static parts of the environment, these being objects that can be pushed or moved by the player and other forces like gravity, the avatars hands can stick on to these objects and then be manipulated by the avatar.
Avatar climbing over a ledge.
Using objects to break glass.
Using the hands to attach to the oars, the player can move the avatar forward and backward to move the oars that will then move the boat forward.
Octodad: Dadliest Catch
Octodad has a unique approach to controlling limbs, that is the thumbsticks are used to maneouvre the limbs by moving them across planes as defined by cardinal directions. So for example, a limb is controlled by moving the position of the tip of the limb. It can be moved up and down and from side to side with one thumb stick, and forward and backward and around with the other. One other button is used to grab non-static objects that can be pushed around by a single button.
The button mappings for movement of limbs is mapped to the axes of the thumbsticks. The following directions are in relation to the camera viewpoint. So players can move the limb left and right with both sticks by moving the thumbstick left and right. In the above mapping, up and down is tied to the left thumbstick. The right thumbstick moves the limb forward and backward from the viewpoint of the camera. This method allows for precise controls for each limb.
Moving limb up Moving limb down
Moving limb left Moving right
Moving backwards Moving forwards
Manipulation of the legs is slightly different from the arms, the default mappings have trigger buttons that lift the legs. They also change the thumbstick controls to affect the legs instead of the arms. Moving any limb far enough would result in pulling the avatar towards that direction. However, the feet have high mass when not active so the avatar can only stretch so far.
Pressing and holding the trigger will raise the leg Letting go of the trigger drops the leg
When moving the leg, the thumbsticks only move teh legs forward, backward, left and right. This lack of vertical control results in less control over the leg, however this seems to make sense as it reinforces the leg as a form of traversal and reinforces the arms as a form of interaction with objects.
Objects can be grabbed with limbs These stick to the end of the limb until the grab button is pressed again
Multiple objects can be grabbed by the player with the tip of the limb with a dedicated button press. These can be used to accomplish objectives. For example, one objective was to cook burgers on a grill, this involved picking up and placing the burgers onto the grilland picking them up and serving them again after it has cooked for some time. Another objective was navigate through freezers to acquire a pizza, this required manipulating the avatar through small spaces by leading the body with the limbs.
The avatar can also push and move objects simply by colliding with them, this usually results in chaos as objects fly around the level. There are also some moving objects like platforms that can move the avatar around.
What can be used
- Thumbsticks for precise limb controls. Octodad’s use of thumbsticks allows intuitive and precise controls of the limbs, this would be useful for grabbing and dropping objects.
- Grabbing mechanic. Grabbing is found to be one of the most important mechanics in both games and allows the player to interact with other parts of the game.
- Static and non-static objects interacted with the grab action. Human: Fall Flat’s environment can be interacted with the grab actions, either to grab and move an object or to stick the avatars hands to the surface.
- Object interactions via avatar movement. In both games objects are used to accomplish certain goals and actions. Human: fall flat allows the player to row a boat via grabbing both oars and moving the avatar forward and backward to row the boat. In Octodad a Segway can controlled with both arms to accelerate the Segway backward or forward.
- Stepping mechanics. Octodad focuses buttons for controlling specific legs to move the avatar forward.
Next Steps
The above will be implemented with the current prototype. These additions will then be tested internally and externally to see if these controls are accurate and without too much difficulty. More importantly controller input will be implemented with the game.
References
- No Brakes Games, Code Glue, d3t, Lab42, 2016. Human: Fall Flat. [Video Game] Windows, Linux, MacOS, Playstation 4, Xbox One, Nintendo Switch, Android, iOS, Xbox Series X/S, Playstation 5, Curve Digital, 505 Games.
- Young Horses, 2010. Octodad: Dadliest Catch. [Video Game] Android, iOS, Linux, Microsoft Windows, Nintendo Switch, OS X, Playstation 4, PlayStation Vita, tvOS, Wii U, Xbox One. Young Horses.