Touch

Clicking an object raises touch events in its scripts, and the detected functions tell who touched, which prim and exactly where. Touch needs no permission. Part of the Input feature.

Touch events

• touch_start is triggered when an avatar first touches the object, touch continuously while it touches, and touch_end when it stops
  • Each passes num_detected, the number of touching agents; read who touched with the detected functions
  • llDetectedLinkNumber gives the link number of the touched prim: 0 for an unlinked object, 1 for the root, 2 and up for child prims
• By default touches only trigger events in the touched child prim; child prims can pass touches to the root (see the pass modes)

Constant groups PassMode 3

Touch position

Each function takes the index of the detected touch.

• Face: the index of the clicked face, or TOUCH_INVALID_FACE
• Surface coordinates (s, t) and texture coordinates (u, v, affected by repeats and rotation), typically in [0.0, 1.0], or TOUCH_INVALID_TEXCOORD
• Position in region coordinates, or screen-space coordinates on a HUD
• Surface normal and binormal, which together give the tangent space
  • Position, normal and binormal return TOUCH_INVALID_VECTOR when the touch position is not valid

Touch functions and events

event	touch_start(integer num_detected) Triggered when an avatar first touches the object. Passes num_detected, representing the number of touching agents.
event	touch(integer num_detected) Triggered continuously while an avatar touches the object. Passes num_detected, representing the number of touching agents.
event	touch_end(integer num_detected) Triggered when an avatar stops touching the object. Passes num_detected, representing the number of touching agents.
integer	llDetectedTouchFace(integer index) Returns the integer index of the face clicked by the avatar in the touch event specified by index.
vector	llDetectedTouchST(integer index) Returns the surface coordinates (<s, t, 0.0>) where the prim was touched, specified by index. X and Y contain the horizontal (s) and vertical (t) face coordinates, typically in the interval [0.0, 1.0]. Returns TOUCH_INVALID_TEXCOORD if coordinates cannot be determined.
vector	llDetectedTouchUV(integer index) Returns the texture coordinates (<u, v, 0.0>) where the prim was touched, specified by index. X and Y contain the horizontal (u) and vertical (v) texture coordinates, typically in the interval [0.0, 1.0] (affected by repeats and rotation). Returns TOUCH_INVALID_TEXCOORD if coordinates cannot be determined.
vector	llDetectedTouchPos(integer index) Returns the vector position where the object was touched (specified by index) in region coordinates, or in screen-space coordinates if the object is attached as a HUD.
vector	llDetectedTouchNormal(integer index) Returns the surface normal vector (perpendicular to the surface) at the touched location specified by index. Can be used with llDetectedTouchBinormal to determine the tangent space.
vector	llDetectedTouchBinormal(integer index) Returns the surface binormal vector (tangent to the surface, pointing along the positive T (V) direction of tangent space) at the touched location specified by index. Can be used with llDetectedTouchNormal to determine the tangent space.
integer	llDetectedLinkNumber(integer number) Returns the link number (integer) of the triggered event (touches and collisions only) specified by number. Returns 0 for non-linked objects, 1 for the root prim, and 2+ for child prims. Returns 0 if not supported by the event.
key	llDetectedKey(integer number) Returns the key (UUID) of the detected object or avatar specified by number, or NULL_KEY if number is not a valid index.
void	llPassTouches(integer pass) Sets the pass-touches attribute. If pass is TRUE, touch events are passed from child prims to the root; if FALSE (default), they only trigger events in the affected child prim.
void	llSetClickAction(integer action) Sets the action (a CLICK_ACTION_* flag) performed when an avatar left-clicks the prim.
void	llSetTouchText(string text) Displays the string text instead of 'Touch' in the right-click context menu.

See also Category TouchSL Wiki LSL Touch PositionSL Wiki Script library: touch detectionPlanned Recipe: buttons on one prim with touch positions

Click actions and touch text

• llSetClickAction sets what a left-click on the prim does, with an action from the CLICK_ACTION_* click actions
  • Per prim through llSetLinkPrimitiveParamsFast with PRIM_CLICK_ACTION, followed by a CLICK_ACTION_* constant
• llSetTouchText shows text instead of “Touch” in the right-click menu

Constant groups ClickAction 11