RoomPlan: Use the transform and dimensions to generate 4 corner points

Question

mike.normal13 OP

Created Jun ’22

Replies 5

Boosts 1

Views 2.4k

Participants 6

I'm trying to use data returned from the RoomCaptureSession delegate to draw four corners of a door in SceneKit.

The CapturedRoom.Surface class has Dimensions and Transform members.

I was told in the WWDC 2022 RoomPlan Slack lounge:

"You can use transform and dimensions parameters to draw lines. The 4 corners can be inferred from those 2 parameters: the first column of the transform is the "right" vector, and second is the "up" vector. The fourth column is the position of the wall/door/opening/window/object Combining those unit vectors with the dimensions vector will give you the corners."

So I think this is a basic vector question. I'm not sure what is meant by "Combining those unit vectors with the dimensions vector". I've tried a few things, but I'm not sure how to go about this.

Answered by mike.normal13 in 717009022

So this is how I pulled something of kind of quick and dirty.

The dimensions vector is [width, height, length]

And the central point of the door can be defined as: Point(door.transform[3].x, door.transform[3].y, door.transform[3].z)

I'm seeing the length come up as zero for doors.

So I defined the upper left point as:

upperLeftPoint = Point(centerPoint) 
upperLeftPoint = upperLeftPoint.translate(rightV.negate(), doorWidth/2) 
upperLeftPoint = upperLeftPoint.translate(upV, doorHeight/2)

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Answer 1

mike.normal13 OP

Jun ’22

I found it

0

Answer 2

mike.normal13 OP

Jun ’22

Accepted Answer

So this is how I pulled something of kind of quick and dirty.

The dimensions vector is [width, height, length]

And the central point of the door can be defined as: Point(door.transform[3].x, door.transform[3].y, door.transform[3].z)

I'm seeing the length come up as zero for doors.

So I defined the upper left point as:

upperLeftPoint = Point(centerPoint) 
upperLeftPoint = upperLeftPoint.translate(rightV.negate(), doorWidth/2) 
upperLeftPoint = upperLeftPoint.translate(upV, doorHeight/2)

1

Answer 3

Dev_Studios OP

Sep ’22

Can you please post the solution

0

Answer 4

ajay215 OP

Nov ’22

Hi, below is code to extract four corner points of wall from its dimensions and transform matrix.

center = transform[3]
rightVector = transform[0]
upVector = transform[1]

angle = atan2f(dimensions.y/2, dimensions.x/2)

diagonalDistance = sqrt(dimensions.x/2 * dimensions.x/2 + dimensions.y/2 * dimensions.y/2)

move =  CGPoint(x: diagonalDistance * cos(angle), y: diagonalDistance * sin(angle))

topLeftPoint = center.translate(x: rightVector.x * move.x + upVector.x * move.y, 
                                y: rightVector.y * move.x + upVector.y * move.y, 
                                z: rightVector.z * move.x + upVector.z * move.y)

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Answer 5

Gavin-Jiang OP

Nov ’24

here is sample swift code to calculation the room corners: let dim = wall.dimensions

        let t = wall.transform
        let pos = simd_float3(x: t.columns.3.x, y: t.columns.3.y, z: t.columns.3.z)
        let right = simd_float3(x: t.columns.0.x, y: t.columns.0.y, z: t.columns.0.z)
        let up = simd_float3(x: t.columns.1.x, y: t.columns.1.y, z: t.columns.1.z)

        let end0 = pos - right * dim.x / 2 - up * dim.y / 2
        let end1 = pos + right * dim.x / 2 + up * dim.y / 2

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