Collision detection

CoppeliaSim can detect collisions between two collidable entities in a flexible way. The calculation is an exact interference calculation. Collision detection, as its name states, only detect collisions; it does however not directly react to them (for collision response, refer to the dynamics module).

[Collision detection between two manipulators]

Using the API function sim.checkCollision, one can easily detect collision between entities, for instance collision detection between a robot and its environment, from within a child script, in each simulation step:


function sysCall_init()
    local robotBase=sim.getObject('/robotModelAlias')
    robotCollection=sim.createCollection(0)
    sim.addItemToCollection(robotCollection,sim.handle_tree,robotBase,0)
end

function sysCall_sensing()
    local result,pairHandles=sim.checkCollision(robotCollection,sim.handle_all)
    if result>0 then
        print('Robot is colliding. Colliding pair is '..getAsString(pairHandles))
    end
end

One can also temporarily modify the color of objects or whole collections, in order to visually indicate a collision:


function changePairColor(entityPair,colorPair)
    originalColorData={}
    originalColorData[1]=sim.changeEntityColor(entityPair[1],colorPair[1])
    originalColorData[2]=sim.changeEntityColor(entityPair[2],colorPair[2])
end

function restorePairColor()
    if originalColorData then
        sim.restoreEntityColor(originalColorData[1])
        sim.restoreEntityColor(originalColorData[2])
        originalColorData=nil
    end
end

function sysCall_init()
    local robotBase=sim.getObject('/irb360')
    robotCollection=sim.createCollection(0)
    sim.addItemToCollection(robotCollection,sim.handle_tree,robotBase,0)
    collisionColors={{1,0,0},{1,0,1}} -- collider and collidee
end

function sysCall_sensing()
    local result,pairHandles=sim.checkCollision(robotCollection,sim.handle_all)
    restorePairColor()
    if result>0 then
        -- Change color of the collection and the collidee:
        changePairColor({robotCollection,pairHandles[2]},collisionColors)
        -- Change color of the collider and collidee objects:
        -- changePairColor({pairHandles[1],pairHandles[2]},collisionColors)
    end
end

function sysCall_cleanup()
    restorePairColor()
end

CoppeliaSim's collision detection functionality is also available as stand-alone routines via the Coppelia geometric routines.

See also the add-on Collision check that allows to quickly check for self-collision, collision with the environment, or collision between two entities.