[alexandra.grohmann]

Hello!

We have a problem with our Felgo Game. We try to implement an “Unblock Me” Game. The aim is it to bring the pink block to the right of the gamearea.

Now we can move the vertical stones up and down and the horizontal stones left and right.

We move the stones via a MouseArea and would like to implement a BoxCollider to realize if a stone collides with another stone. The problem is how to say, that if there is a Collision, the stone should not move forward.

If the stones now collides with another stone, we put down their opacity only to test if the BoxCollider works.

We hope you can help us.

Best regards, Alexandra

The first pictures shows our current game, the second picture is the qml-file of our pink block.

[ChristianFelgo Team]

Hi Alexandra,

you can stop the movement of the stone, by setting the enabled property of MouseArea to false in fixture.onBeginContact. That way, the dragging of the stone is stopped.

Cheers,
Chris

[alexandra.grohmann]

Do you think so?

fixture.onBeginContact: {
mouse.enabled = false
}

because then the stone stops, but he is “inside” the next stone and not before

Best regards, Alexandra

[ChristianFelgo Team]

Yes that was what I was thinking of!

Are you sure your colliders are correctly set up and match the visual representation? Please go to main.cpp and turn on the qmlRenderer, to verify that.

You can also get the position of the entity at your collision point and add the half of the width to it, so you will also receive the position where your collision took place.

Cheers,
Chris

[johanna_g18]

Further, there is the problem that if the stone was stopped once, we can never move it again. I think there should be code like this:

mouse.enabled = true

but where?

Best wishes,
Johanna

[ChristianFelgo Team]

That’s a very good question!

The problem is, that after disabling the MouseArea, no onReleased gets called so you cannot re-enable it at that time. So I think it may be better to not disable it, but instead set the drag.target to another (temporary) item, and in onReleased set it back to your entity.

The code would look something like that:

import VPlay 1.0
import QtQuick 1.1

EntityBase {
  id: entity

  MouseArea {
    id: mouseArea
    anchors.fill: parent
    drag.target: entity

    onReleased: {
      // set it to the entity again, so it can be re-dragged
      mouseArea.drag.target = entity
    }
  }


  Item {
    // this gets only used to avoid dragging the entity when a collision occured
    id: temporaryDragTarget
  }

  BoxCollider {
    // ... your boxCollider information here ...

    fixture.onBeginContact: {
      // avoid dragging further, when a collision was reached
      mouseArea.drag.target = temporaryDragTarget
    }
  }
}

Cheers,
Chris

[alexandra.grohmann]

Ok, it is working now.
But there is still the problem that, if I move a stone and he collides with an other stone that the stones are overlapping.
I have noticed, that when i move the stone faster it is more over the edge of the other stone and when i move it slower it stops in front of the stone or is a little bit overlapping.

[ChristianFelgo Team]

Yes that sounds reasonable. You could solve that by calculating your non-overlapping position by using the size of the collided entity, and the size of your entity. You can then set the entity position to be outside of the collision range.

See the fixture.onBeginContact doc how to get the body of the collided entity: http://doc.felgo.com/qml-components-fixture.html#onBeginContact-signal

Cheers,
Chris

[alexandra.grohmann]

We have now set the drag target to a temporary item and calculated the position to be outside but the stones are still flickering if they collide.

Our Code in one standing stone looks like:

        fixture.onBeginContact: {
            mouse.drag.target = temp

            var collidedColliderComponent  = other.parent.parent
            var collidedEntity = collidedColliderComponent.parent

            if(collidedEntity.y > entity.y) {
                entity.y = collidedEntity.y - entity.heigth - 1
            } else {
                entity.y = collidedEntity.y + collidedEntity.heigth + 1
            }
        }

 

Do we need another collider component or should this work?

 

Greeting,

Alexandra

[David]

Hi Alexandra,

maybe you want to rethink your physical concept. Basically there are two ways how to handle and use physic systems:

1. Only use collision detection without physics effects (logic needs to be implemented by your own, which is kinda tricky) – which is your current approach.
2. Use the complete physic system with real collisions and physical effects. Might be easier!

If you try approach two, you can see the StackTheBoxDemo which handels already boxes, such as your blocks which can be dragged and moved around with a Mouse Joint. You can restrict the movement direction by defining the correct target point. This is the MouseJoint from StackTheBoxDemo but with the restriction of movement only into x direction archieved in onPositionChanged.

 

        MouseArea {
            anchors.fill: parent

            property Body selectedBody: null
            property MouseJoint mouseJointWhileDragging: null

            onPressed: {

                selectedBody = physicsWorld.bodyAt(Qt.point(mouseX, mouseY));
                console.debug("selected body at position", mouseX, mouseY, ":", selectedBody);
                // if the user selected a body, this if-check is true
                if(selectedBody) {
                    // create a new mouseJoint
                    mouseJointWhileDragging = mouseJoint.createObject(physicsWorld)

                    // set the target position to the current touch position (initial position)
                    mouseJointWhileDragging.targetPoint = Qt.point(mouseX, mouseY)

                    // connect the joint with the body
                    mouseJointWhileDragging.movingBody = selectedBody

                    // set the physicsWorld where the joint should be created
                    mouseJointWhileDragging.world = physicsWorld
                }
            }

            onPositionChanged: {
                // this check is necessary, because the user might also drag when no initial body was selected
                if (mouseJointWhileDragging && selectedBody) {
                  mouseJointWhileDragging.targetPoint = Qt.point(mouseX, selectedBody.parent.parent.y)
                }
            }
            onReleased: {
                // if the user pressed a body initially, remove the created MouseJoint
                if(selectedBody) {
                    selectedBody = null
                    if (mouseJointWhileDragging)
                        mouseJointWhileDragging.destroy()
                }
            }
        }

 

Cheers,

David