Adding Component to Grasshopper Canvas with Python

Hello,

Is it possible to add a Grasshopper component (i.e. a slider) to the grasshopper canvas with python script? I am aware of an example of doing so with C#, but am finding it difficult to do so in python.

For example, a sample script would involve prompting the user to select points on the Rhino canvas, and I would like the python script to create a slider for each point that the user selected on the grasshopper canvas.

Any advice would be greatly appreciated!

Tracy H.

Replies to This Discussion

Permalink Reply by Stephen Maher on August 17, 2015 at 3:45pm

Hi Tracy,

Try this. It creates a basic slider with a lower limit of 0.000 and an upper limit of 1.000. Its default value is 0.250. The slider is placed at the top left of the canvas work space. Edit the script per your needs.

Best,

/SPM

Attachments:

addSlider.gh, 4 KB

Permalink Reply by Tracy Huynh on August 17, 2015 at 7:09pm

Wow--this is very helpful. Many thanks!

My next attempt is to add the slider to the same Python Script component (the "y" input slot for example). I'm working with the lead of the AddSource method (attached), but so far have been unsuccessful. Any advice for this task would be most greatly appreciated!

Tracy H.

Permalink Reply by David Rutten on August 17, 2015 at 4:28pm

If you know the ComponentID of the object you wish to place, you can use one of the GH_Canvas.InstantiateNewObject overloads. It allows you to specify where you want the component to be.

Permalink Reply by Tracy Huynh on August 17, 2015 at 7:15pm

Thank you, David. I am having trouble with the four input parameters for the InstantiateNewObject method (id, init_code, at, update).

I've sifted through the Grasshopper SDK help database, but can't seem to find out to obtain the appropriate ID of the slider component with the creation method (AddObject) above to feed to this method. I can't seem to find what "init_code" and "update" are supposed to provide.

It seems that "at" requires a PointF (not sure what this means for python, but i'm assuming the coordinates of a specific point), but rather than indexing a location on the canvas, is there a way to attach it to the Python Script component itself? I've attempted so with the AddSource method (attached in the reply above), but so far have been unsuccessful.

Many thanks for your time and advice!

Permalink Reply by Stephen Maher on August 17, 2015 at 7:32pm

Hi, David. I forgot about using overloads. Don't think I'm using it correctly though. I quickly tried to adjust the previous code but it keeps crashing Rhino/Grasshopper. What am I missing here?

import Grasshopper as gh
import random as r
import System.Drawing as sd

ghdoc = ghenv.Component.OnPingDocument()
canvas = gh.GUI.Canvas.GH_Canvas()

def createSlider():
mySlider = gh.Kernel.Special.GH_NumberSlider()
id = mySlider.ComponentGuid
mySlider.SetSliderValue(0.25)

x = r.randint(0,100)
y = r.randint(0,100)

ptF = sd.PointF(x,y)

bool = gh.GUI.Canvas.GH_Canvas.InstantiateNewObject(canvas, id, ptF, False)
return mySlider

mySlider = createSlider()
ghdoc.AddObject(mySlider, bool, 1)

Thanks,

/SPM

Permalink Reply by Andrew Heumann on August 17, 2015 at 8:39pm

A few issues I see - one is that you're instantiating a new instance of GH_Canvas instead of using the currently active one, which can be accessed via gh.Instances.ActiveCanvas. I also couldn't get "InstantiateNewObject" to work, but I don't mind the AddObject method.

The code below also provides an example of how to hook the slider up to the python component. This gets a little bit tricky - because you're creating objects that are supposed to be a part of a solution, while a solution is actually happening. Ideally, you should 1. make sure that you check that a slider hasn't already been created, so you don't add a slider every single time the component solves, and 2. schedule a solution AFTER the current solution so that slider value is actually correctly passed into the python component. I haven't provided examples of either of those operations for now.

import Grasshopper as gh import System.Drawing as sd

comp = ghenv.Component ghdoc = comp.OnPingDocument() canvas = gh.Instances.ActiveCanvas

#create the slider Slider = gh.Kernel.Special.GH_NumberSlider()

#add the slider ghdoc.AddObject(Slider,False,ghdoc.ObjectCount+1)

#the array accessor lets you pick which input you want targetInput = comp.Params.Input[1]

thisPivot = targetInput.Attributes.Pivot #set the slider location Slider.Attributes.Pivot =sd.PointF(thisPivot.X-200,thisPivot.Y-10)

#connect the slider targetInput.AddSource(Slider)

Permalink Reply by Andrew Heumann on August 17, 2015 at 8:51pm

Here's a more complete example that does the two things I described in the above post. If you DON'T expire the solution, you'll notice that, even if you change the slider, the python component won't see "y" as having any input.

import Grasshopper as gh import System.Drawing as sd

comp = ghenv.Component ghdoc = comp.OnPingDocument() canvas = gh.Instances.ActiveCanvas

#the array accessor lets you pick which input you want targetInput = comp.Params.Input[1]

#Define a function to expire this component. We'll need this later! def expireThis(doc): comp.ExpireSolution(False)

#Make sure the input doesn't already have a slider if targetInput.Sources.Count==0: #create the slider Slider = gh.Kernel.Special.GH_NumberSlider() #add the slider ghdoc.AddObject(Slider,False,ghdoc.ObjectCount+1) thisPivot = targetInput.Attributes.Pivot #set the slider location Slider.Attributes.Pivot =sd.PointF(thisPivot.X-200,thisPivot.Y-10) #connect the slider targetInput.AddSource(Slider) #Recompute this component so that it has access to the value of the slider ghdoc.ScheduleSolution(5,expireThis)

#Do something with the value: a = y

Permalink Reply by Stephen Maher on August 17, 2015 at 9:05pm

Thanks, Andrew. I caught the ActiveCanvas after posting (one of those silly "face palm" moments).

The Pivot trick is slick. It addresses why I was looking into the "InstantiateNewObject" method well.

I created a boolean input so I can expire the solution. I noticed it was really slowing down GH and every time I changed the slider's value it jumped back to its creation point.

Permalink Reply by Stephen Maher on August 17, 2015 at 9:26pm

Silly addition, but if you replace "targetInput" with the following: