[SNIPPET] Using a Touch to select an object

[dpharaoh]

This took me a few hours to get correct, so I thought I would post a solution. If you are reading this, it's probably because you need to know how to use a touch instead of a mouse event to cast a ray into a scene to see which object is there.

The touch events do not include ray info, but it's easily calculated by us in really just a few lines of script.

In the example below, nX0 and nY0 are the touch events passed in through the touch API. They range from -1 to 1.

Code: Select all

    --[[nX0 and nY0 are the touch events passed in through the touch API, to onTouchesChanged for example. They range from -1 to 1]]--
    local cam = application.getCurrentUserActiveCamera ( )
    local s = application.getCurrentUserScene ( )
    local camX, camY, camZ  = object.getTranslation ( cam, object.kGlobalSpace )
    local nRayPntX, nRayPntY, nRayPntZ = camera.unprojectPoint ( cam, nX0, nY0, 0 )
    local vX,vY,vZ = math.vectorSubtract ( nRayPntX, nRayPntY, nRayPntZ, camX, camY, camZ )
    local nRayDirX,nRayDirY,nRayDirZ = math.vectorNormalize ( vX, vY, vZ )
   
    if  ( s )
    then
        local hHitObject, nHitDist, nHitSID = scene.getFirstHitSensor( s, nRayPntX, nRayPntY, nRayPntZ, nRayDirX, nRayDirY, nRayDirZ, 2000)
        if  ( hHitObject )
        then
            log.message ( "Hit Sensor ID :" .. nHitSID )
        end
    end


If you needed this, I am happy to have provided it, it is a real deal breaker for some projects ;)

[NiCoX]

This is exactly what the engine does for onMouseXXX handlers :cheer:

(just saw both your question and your solution :))

[clockmaster]

Thank you very much for this Code Snippet. That was one of the next Tasks, I have to do for my Game. You are really Great.

[Piedcarre]

Great! Thank you it will probably be very useful for many members :)

[dpharaoh]

My pleasure! One less question for you guys to handle so you can focus on other juicy stuff ;)

[psk]

Id vote this a win if i had a button

[DoctorPepper]

This is amazing, just what i was searching for! Still dont understand why its not in the engine by default

[FR_dZastrX]

Thank you, I was still a few hours from finding it because I tried to use "project" instead of "unproject"
I guess I am a dumb, ...However, some "more" pictures in the Shiva Documentation (Website) could help, in some future, dumbs like me

I am agree this may not be the more juicy thing to plan right now, but, well, that's the kind of tasks young students might be able to do, more or less for free, during some developer stage...? Well, as far as they are not as dumb as me !

[fzuleta]

wow seriously thanks for this

[Selzier]

Thanks dpharaoh! It's still being put to use!

[oo7]

How to get the nX0 and nY0 for onTouchSequenceBegin and onTouchSequenceEnd events?

[dpharaoh]

They are passed in to both those functions by Shiva and are automatically available.

[Lourdez]

Hi !

I've tried this code but I can't get any hit object. Is there anyone who has a sample working ?

Thanks

[dpharaoh]

It is working off of sensors right now. I usually add collision to the mix, so it can pick either an object with sensors or an object with collision. It's really up to you and how you want to have your logic.

[Selzier]

Here is my working example. I tried to comment the code as good as possible. This is in AI model AICamera which is attached to the player's camera.

Code: Select all

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function AICamera.onActivateShoot (  )
--------------------------------------------------------------------------------
   
    local hUser = application.getCurrentUser ( )
   
    -- Get a handler to the player camera
    local o = this.getObject ( )

    -- Get a handler to the scene
    local s = object.getScene ( o )

    if ( s ~= nil )
    then
        -- Get the camera's translation and direction so we know where to shoot a ray from and to
        local nRayPntX, nRayPntY, nRayPntZ = object.getTranslation ( o, object.kGlobalSpace )
        local nRayDirX, nRayDirY, nRayDirZ = object.getDirection ( o, object.kGlobalSpace )
       
        --Shoot a ray looking for a Sensor, with ray length 150 and sensor ID between 0 and 99
        local hHitSensorObject, nHitSensorDist, nHitSensorSurfaceID = scene.getFirstHitSensorWithIDInRange ( s, nRayPntX, nRayPntY, nRayPntZ, nRayDirX, nRayDirY, nRayDirZ, 150, 0, 99 )
                                     
        -- If the ray hit a sensor and the distance is less than 2 meters
        -- I want this to only work for very close objects in my case!
        if ( hHitSensorObject and nHitSensorDist < 2 )
        then
           
            -- Get the string name of the model that was hit
            local sSensor = object.getModelName ( hHitSensorObject )
            -- Get the string name of the AI Model hit
            local sAIModel = object.getAIModelNameAt ( hHitSensorObject, 0 )
           
            log.message ( "hHitSensorObject   : " .. sSensor )
            log.message ( "nHitSensorDist     : " .. nHitSensorDist )
            log.message ( "sAI   at index 0   : " .. sAIModel )
           
            -- Send an onTouch Event Handler to the object that was hit
            -- All my objects that may be hit have an AI Model with a custom "onTouch" handler
            object.sendEvent ( hHitSensorObject, sAIModel, "onTouch" )
           
        -- Nothing was hit or it was farther than 2 meters.
        else
            log.message ( "Nothing was hit" )
        end
       
    end

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