Request the top area of this slab?

[yongler]

I want to make GDL for floor slab accessories and request the top area of this slab. I wrote this: n = REQUEST("SLAB_TOP_SURF" , " " , _area ) But it was not successful. May I ask how to write this sentence?

[Pertti Paasky · Accepted solution]

I think the object does not get the area information of the slab, but You can calculate the area from the point information.

https://www.wikihow.com/Calculate-the-Area-of-a-Polygon  this site tells how.

[Barry Kelly]

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@Pertti Paasky wrote:

I think the object does not get the area information of the slab

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This is correct.

@yongler 

SLAB_TOP_SURF is not for use in REQUEST commands.

It is a Global Variable that can be used only in lists or labels - i.e. a label can give you the area of a slab.

As Pertti suggests, you will have to calculate the area from the point information (nodes) of the slab.

I am not quite sure why you would want the area for an accessory object though?

Barry.

[yongler]

Thank you very much！ This is exactly what I want. 

!!!===求板面积，不包括挖洞的=======
data1 = 0.0
data2 = 0.0
FOR i = 1 to points -1  !!!叉乘
	 data1 =  P[i][1] * P[i+1][2] + data1
	 data2 =  P[i+1][1]* P[i][2] + data2 
 next i

slab_area = (data1 - data2 ) /2    !!!单层面积

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[yongler]

I want to create a GDL that generates a building model from slab Accessories Add Ons and calculates the area of the building.
When changing the shape of the slab, the building outline also changes, and the area data changes accordingly. The area data is embedded in this GDL, rather than displayed through labels.

[yongler]

Thank you very much！ This is exactly what I want. 

!!!===求板面积，不包括挖洞的=======
data1 = 0.0
data2 = 0.0
FOR i = 1 to points -1  !!!叉乘
	 data1 =  P[i][1] * P[i+1][2] + data1
	 data2 =  P[i+1][1]* P[i][2] + data2 
 next i

slab_area = (data1 - data2 ) /2    !!!单层面积

 With the calculation method, writing scripts using GDL is so simple.