topic Re: Gable/Hip Overhang and Testing against overlaps in ArcGIS CityEngine Questions

Gable/Hip Overhang and Testing against overlaps

curtedmonds — Mon, 17 Mar 2014 17:47:21 GMT

Hi All,

The problem I face is I would like to create a roof with volume (not just a flat poly but with height extrusion) and overhang.
Then test this overhang (on a gable or hip roof) and remove if it touches another building or roof section.

#1 The complications with this is the roof section overhang (side next to removed one) should adjust accordingly.
#2 The volumes are not just rectangles ..includes T and U based volumes
#3 extrusions should be on whole roof as single poly to avoid internal and unwanted polys.

things stopping me further:

#direction great for rectangles but not for other shapes
doCreateGableRoof(isCorner ) -->
    case scope.sx > scope.sy :
        roofGable(InternalRoofAngle,InternalRoofOverhang, InternalRoofOverhang, false, 1)
        doCreateGableRoofSideRemove(isCorner )
    else:
     roofGable(InternalRoofAngle, InternalRoofOverhang, InternalRoofOverhang, false, 0)
     doCreateGableRoofSideRemove(isCorner )

#test seem to fail when U and T shapes and other unknown volumes > 8 vertex
#tests have to be volumes so I have to cut roof at overlap section
#orientation unknown
#sides don't know if a touch has happened to side next to itself
#false test , one needs to know which is the long section (gable) so a split can be created at length ends to test
and a few others I can remember...

some ideas:
#just move roof up and find way to create overhang after the roof is created (dont know options for this) extrude down to create illusion of roof volume
#slice and dice everything on extruded volume (poly count = 😞 )
#give up...
#find hidden function that does this

any ideas welcome
c

Re: Gable/Hip Overhang and Testing against overlaps

curtedmonds — Sat, 22 Mar 2014 23:00:27 GMT

So ...
This does not seem totally possible with the engine, my rough starting point for those interested:

#insure direction of Gable is aligned
doCreateGableRoof -->
    case scope.sx > scope.sy :
        roofGable(InternalRoofAngle,InternalRoofOverhang, InternalRoofOverhang, false, 1)
        doCreateGableRoofSideRemove(isCorner )
    else:
     roofGable(InternalRoofAngle, InternalRoofOverhang, InternalRoofOverhang, false, 0)
     doCreateGableRoofSideRemove(isCorner )

#get the side section out of a gable roof
doCreateGableRoofSide -->
       comp(f) {top=doCreateGableRoofTest | bottom:NIL | side:col.PINK }

#see if the roof top section has more than 2 faces if so different case (ie:not possible with engine..lots of hacking needed)
doCreateGableRoofVolumeTest-->
case geometry.nFaces() > 2:
   col.RED
else: #this should be triangle overhang
split(x) { InternalRoofOverhang: doSplitTestExtrude
   | ~1: col.ORANGE #middle section,will need another split for long edge
   | InternalRoofOverhang:doSplitTestExtrude
   }

#extrude
doSplitTestExtrude-->
extrude(world.y, -RoofThickness)
doCreateTouch

#test overlap if it overlaps NIL out and clean up edge
doCreateTouch()-->
case overlaps(inter): #overlap so cap end
   split(x) { RoofThickness/2:col.GREEN| ~1:NIL }
   else : # all good so cap end
   split(x) { ~1:col.ORANGE |RoofThickness/2:col.GREEN}

my lesson so far is the programming language needs further development to be considered a complete procedural modeling tool.

Re: Gable/Hip Overhang and Testing against overlaps

curtedmonds — Tue, 25 Mar 2014 17:37:43 GMT

With persistence comes reward...sort of

Cant do it the logical way but....the trick seems to be use edges to "simulate" the overhang and special case the Triangle section
eg:
#section off side of cable ie:Triangle
doSeperateEdgesAndTriangle(isCorner) -->
comp(e) {ridge: i("builtin:cube") s('1, RoofThickness, RoofThickness) center(yz) doGableTopSectionRidge
   | hip: i("builtin:cube") s('1, RoofThickness, RoofThickness) center(yz) doGableTopSectionHip
   | eave: i("builtin:cube") s('1, RoofThickness, RoofThickness) center(yz) doGableTopSectionEave
    }
comp(f) {top=doGableTopSection(isCorner ) | bottom:NIL | side:alignScopeToAxes(y) doGableTriangleSectionAndEdge(isCorner ) }#=doCreateGableRoofTest2 }

#the Triangle section special case example
doGableTriangleSectionAndEdge(isCorner )-->
doGableTriangleSection
comp(e) { 3:NIL | 1: doGableTriangleSectionEdge(isCorner ,1) | 2: doGableTriangleSectionEdge(isCorner ,2) }

hope this helps others, has caused be many late nights and loose hair...again

Re: Gable/Hip Overhang and Testing against overlaps

MatthiasBuehler1 — Wed, 26 Mar 2014 14:21:59 GMT

Hi,

Thanks for the insights ! ( in-sigh-ts ) 🙂