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Libraries & objects
About Archicad and BIMcloud libraries, their management and migration, objects and other library parts, etc.

CUTPLANE from Plane Normal

Contributor
Hi,

Can anyone please tell me how to use the additional [x,y,z] parameters in the CUTPLANE [x, y, z] command. I wish to define a cutplane for a plane that I know 3 x,y,z points for.

I can work out the equation and normal for the plane using the 3 points but dont seem to be able to use the resulting information within the CUTPLANE [x,y,z] command correctly.

Any help would be greatly appreciated.

Kind Regards,
Danny
5 REPLIES 5
The x, y and z represent the break through points of the three axis on the curplane. If you have the plane equation

ax + by+ cz + d = 0

You can set y=0 and z=0 to get the point on the X axis. Similar for the both others.

Maybe you will need a fourth parameter. If you add a "1" at the end, the cutting direction will be flipped.

Can you maybe post the whole formula for the three points?
bim author since 1994 | bim manager since 2018 | author of selfGDL.de | openGDL | skewed archicad user hall of fame | author of bim-all-doors.gsm
Contributor
Thanks for the pointer - I tried applying it to my situation but am still a little stuck - perhaps I have something wrong in my plane equation.

As requested I have posted below my script. I have put all the information and calculations together so this can be copied straight into the 3D script.

Thanks again for your help on this problem.

Kind Regards,
Danny

!-----SET SIZES-----
len=1.0
dep=1.0
wall_thk=0.090

!-----SET POINTS-----
x1=0.0 : y1=0.0 : z1=0.3
x2=1.0 : y2=0.5 : z2=0.6
x3=0.0 : y3=1.0 : z3=0.3

!-----CALCULATE VALUES FOR PLANAR EQUATION-----
co_a=(y1*(z2-z3))+(y2*(z3-z1))+(y3*(z1-z2))
co_b=(z1*(x2-x3))+(z2*(x3-x1))+(z3*(x1-x2))
co_c=(x1*(y2-y3))+(x2*(y3-y1))+(x3*(y1-y2))
co_d=-((x1*((y2*z3)-(y3*z2)))+(x2*((y3*z1)-(y1*z3)))+(x3*((y1*z2)-(y2*z1))))

!-----CALCULATE POINTS FOR CUTPLANE-----
IF co_a#0.0 THEN
x_cut=-co_d/co_a
ELSE
x_cut=1.0
ENDIF

IF co_b#0.0 THEN
y_cut=-co_d/co_b
ELSE
y_cut=1.0
ENDIF

IF co_c#0.0 THEN
z_cut=-co_d/co_c
ELSE
z_cut=1.0
ENDIF

!-----DRAW OBJECT WITH CUTPLANE-----
CUTPLANE x_cut, y_cut, z_cut, 0

PRISM_ 9, 5.0,
0.0, 0.0, 15,
len, 0.0, 15,
len, dep, 15,
0.0, dep, 15,
0.0, dep-wall_thk, 15,
len-wall_thk, dep-wall_thk, 15,
len-wall_thk, wall_thk, 15,
0.0, wall_thk, 15,
0.0, 0.0, -1

CUTEND

END
Done very well, but you trapped into one definition lack:
The three ordinates may not be zero, because these special cases built up a cutplane parallel to one of the three axis.

Try this (copy it to MASTERscript to get PRINT to work).
```!-----SET SIZES-----
len=1.0
dep=1.0
wall_thk=0.090

!-----SET POINTS-----
x1=0.2 : y1=0.0 : z1=0.3
x2=1.0 : y2=0.5 : z2=0.6
x3=0.0 : y3=1.0 : z3=0.3

!-----CALCULATE VALUES FOR PLANAR EQUATION-----
co_a=(y1*(z2-z3))+(y2*(z3-z1))+(y3*(z1-z2))
co_b=(z1*(x2-x3))+(z2*(x3-x1))+(z3*(x1-x2))
co_c=(x1*(y2-y3))+(x2*(y3-y1))+(x3*(y1-y2))
co_d=-((x1*((y2*z3)-(y3*z2)))+(x2*((y3*z1)-(y1*z3)))+(x3*((y1*z2)-(y2*z1))))

!-----CALCULATE POINTS FOR CUTPLANE-----
IF co_a#0.0 THEN
x_cut=-co_d/co_a
ELSE
x_cut=0
ENDIF

IF co_b#0.0 THEN
y_cut=-co_d/co_b
ELSE
y_cut=0
ENDIF

IF co_c#0.0 THEN
z_cut=-co_d/co_c
ELSE
z_cut=0
ENDIF

!-----DRAW OBJECT WITH CUTPLANE-----
if x_cut and y_cut and z_cut THEN CUTPLANE x_cut, y_cut, z_cut, 0

PRISM_ 9, 5.0,
0.0, 0.0, 15,
len, 0.0, 15,
len, dep, 15,
0.0, dep, 15,
0.0, dep-wall_thk, 15,
len-wall_thk, dep-wall_thk, 15,
len-wall_thk, wall_thk, 15,
0.0, wall_thk, 15,
0.0, 0.0, -1

if x_cut and y_cut and z_cut THEN CUTEND

!-----DRAW SPANING PLANE-----

MATERIAL "Glas"
PLANE 3,
x1,y1,z1,
x2,y2,z2,
x3,y3,z3

!-----RECALCULATE POINTS IN PLANE-----

PRINT "If all Points are on the Plane, represented by the equation, all following results sould be zero."
PRINT "POINT 1: ",co_a*x1+co_b*y1+co_c*z1+co_d
PRINT "POINT 2: ",co_a*x2+co_b*y2+co_c*z2+co_d
PRINT "POINT 3: ",co_a*x3+co_b*y3+co_c*z3+co_d
PRINT "The constants a/b/c/d: ",co_a,"/",co_b,"/",co_c,"/",co_d
END```
bim author since 1994 | bim manager since 2018 | author of selfGDL.de | openGDL | skewed archicad user hall of fame | author of bim-all-doors.gsm
You could proof, if one of the ordinates is zero and could calculate one other point on plane by inserting anything as x and y in the equation. Then repeat the ordinate calculation (-> make ab sub for it).
bim author since 1994 | bim manager since 2018 | author of selfGDL.de | openGDL | skewed archicad user hall of fame | author of bim-all-doors.gsm
Contributor
Thanks for the help and the response. I have built in the parallel axis checking and it works exactly how I require.

Danny

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