Traços & Raycasting

Como usar trilhas & Raycasting para coletar informações do mundo em tempo de execução.

Traces oferecem um método para alcançar seus mapas e obter feedback sobre o que está presente ao longo de um segmento de linha. You use them by providing two end points (a start and end location) and the physics system “traces” a line segment between those points, reporting any Actors that it hits. As trilhas são essencialmente as mesmas que Raycasts ou Raytraces em outros pacotes de software.

O exemplo a seguir mostrará como obter o quê e para onde o jogador está olhando.

Client/Index.lua

-- Traces at each 100ms
Timer.SetInterval(function()
    -- Gets the middle of the screen
    local viewport_2D_center = Viewport.GetViewportSize() / 2

    -- Deprojects to get the 3D Location for the middle of the screen
    local viewport_3D = Viewport.DeprojectScreenToWorld(viewport_2D_center)

    -- Makes a trace with the 3D Location and it's direction multiplied by 5000
    -- Meaning it will trace 5000 units in that direction
    local trace_max_distance = 5000

    local start_location = viewport_3D.Position
    local end_location = viewport_3D.Position + viewport_3D.Direction * trace_max_distance

    -- Determine at which object we will be tracing for (WorldStatic - StaticMeshes - and PhysicsBody - Props)
    local collision_trace = CollisionChannel.WorldStatic | CollisionChannel.PhysicsBody

    -- Sets the trace modes (we want it to return Entity and Draws a Debug line)
    local trace_mode = TraceMode.ReturnEntity | TraceMode.DrawDebug

    -- Last parameter as true means it will draw a Debug Line in the traced segment
    local trace_result = Trace.LineSingle(start_location, end_location, collision_trace, trace_mode)

    -- If hit something draws a Debug Point at the location
    if (trace_result.Success) then

        -- Makes the point Red or Green if hit an Actor
        local color = Color(1, 0, 0) -- Red

        if (trace_result.Entity) then
            color = Color(0, 1, 0) -- Green

            -- Here you can check which actor you hit like
            -- if (trace_result.Entity:GetType() == "Character") then ...
        end

        -- Draws a Debug Point at the Hit location for 5 seconds with size 10
        Debug.DrawPoint(trace_result.Location, color, 5, 10)
    end
end, 100)

tip

As you could see, we can pass bit-wise operators to Trace for more than one CollisionChannel at once! Use ➲ entre os CollisionChannels para conseguir isso.