Little help?

mut

Hi guys,

I modified a stair.rb script ages ago, to better suit how i work, but i just wondered if any of you guys could help me out in this one area:

basically i use: entities.add_face(point1, point2, point3, point4) etc, but i would like to add an 8mm radius between some of the points. i am an absolute beginner in this (I have done some basic jscript/java/php etc, but nothing with ruby/sketchup), and i am having trouble finding an answer to this question.

thanks,

Tom.

TIG

Imagine you are drawing it with a pencil...
You have 4 points as 'dots' on the paper (p1,p2,p3,p4), that would form a rectangle.
For ease lets assume that points p1 and p2 are to have 8mm radius corners.
You need to make some extra points 8mm away from these - lets called p1's p1a and p1b, and p2's p2a and p2b. You need to think along which edge's 'line' these points will be located...
If you were to draw the edges p1a,p2a and p1b,p4 and p2b,p3 and p3,p4, you'd have a rectangle with two parts of its corners missing - where you'd add the arcs. Once the arcs are put in it's a complete loop that would face.

Instead of using the "entities.add_face(p1,p2,...)" method you have to use "my_edge=entities.add_line(p1a,p2a)", then "entities.add_line(p1b,p4)" and so on to add the four edges (note there's no face just yet).

Then use "entities.add_arc(center,xaxis,normal,radius,start_angle,end_angle,numsegs)" to add in the arc(s) to complete a loop of edges and arcs that could take a face.

Arc making looks complex but once you work out what the various bits do it's not too bad...
Let's assume this is 'flat' in the Z...
center - e.g. it's p1ax = p1a offset in (say) the X by 8mm - it'll vary depending where the arc lies in the loop...
xaxis = Geom::Vector3d.new(1,0,0) i.e.it's flat.
normal = (Geom::Vector3d.new(0,0,1)).normalize to match 'flat' arc
radius = 8.mm
start_angle = 0.degrees
end_angle = 90.degrees

angles are in radians but you can enter them in degrees like this for sanity's sake !

for these angle bits you'll need to experiment to see what suits your arcs' orientations etc

'optional' numsegs = 8 [or however many segments you want in the arc] - more segments give smoother curves BUT multiply up the edges/faces exponentially when pushpulled, with little visual benefit...

Finally use "my_face=my_edge.find_faces" to make the face that can exist within 'entities' that use these edges and arcs...

I assume you'll then 'pushpull' the my_face to make a tread or something ? To avoid lines forming where an arc meets a straight edge you could add the arc and its two abutting edges to a curve entity first - then its extrusion would be 'smooth'... but let's get the basics first...

.

mut

thanks alot for the help TIG, really well explained (even i can understand it hehe)
its working fine so far (in that it now creates the profile of the tread with rounded corners etc, )

so now i have:

tread_edge1 = entities.add_line([0, 0, radius], [0, 0, tt - radius]) #this is the short striaght edge at the front
tread_edge2 = entities.add_line([radius, 0, tt], [tread + nosing, 0, tt], [tread + nosing, 0, 0], [nosing + rt, 0, 0], [nosing + rt, 0, rd], [nosing, 0, rd], [nosing, 0, 0], [radius, 0, 0]) # rest of the tread
tread_bottrad = entities.add_arc(bottcenter,bottxaxis,bottnormal,radius,bottstart_angle,bottend_angle) #bott radius
tread_toprad = entities.add_arc(topcenter,topxaxis,topnormal,radius,topstart_angle,topend_angle) #top radius

then i did

tread_base = tread_edge1.find_faces

which creates the face just fine, but when i add the line:

tread_base.pushpull treadwidth

sketchup does nothing (not even draw the initial outline)

any suggestions?

thanks again,

Tom.

TIG

My mistake... 'find_faces' returns the number of faces it makes not the face itself ! Was going from memory - which is clearly failing...

Try this:

tread_base=tread_edge1.faces[0]

the 0 = the first face that the edge has (I assume it'll only have the one face)

Then:

tread_base.pushpull(treadwidth)

It should now work...
.

mut

thats cracking!

Thanks a lot, was having a bit of trouble with that part.

it pretty much works now! gotta just figure a bit more maths out to do with width/depth of the stringers, and im good to go

thanks,

Tom.

TIG

Good...

Next make a spiral staircase !

.

mut

gimme ten mins