# Polynomial curve sketching on blender

I know that blender is able to draw mathematics curves using function, example:

How to draw a flat ellipse surface in Blender with the following known dimensions?

Is there any code or method to insert a function $$f(x)$$ and get the curve?

How to limit the points of the curve as in the example in red?

Above, an ellipse is drawn in blender using the Bezier curve, through code and mathematical equations, to exemplify this question.

• try something similar to the python code in: blender.stackexchange.com/questions/271855/… then just create a loop with $px$ iterating from range $2-8$ and u will get the resulting $py$ with substituting each $x$ into your equation $py=0.09x^2+0.42x+0.49$. then plot it with $pz=(0,0,0)$ since your case is just 2 dimensional. Aug 13 at 9:48
• This codes works! Aug 13 at 18:12

Try this script. Notice that your $$f(x)$$ function is in the get_graph_y definition which accepts an x value input in the range $$2-8$$ and computes its corresponding y value from the function. You can change the range and the function to anything as long as its of the form $$y=y(x)$$ and the script will plot the graph.

import bpy

def get_object(name):
objects = bpy.context.scene.objects
if name in objects:
return objects[name]
m = bpy.data.meshes.new(name + "-mesh")
o = bpy.data.objects.new(name, m)
#o.modifiers.new(name, 'SKIN')
return o

def get_range(start, end, step = 2):
return [v * 0.1 for v in range(start * 10, end * 10, step)]

def get_graph_y(x):
return 0*x**3 - 0.09*x**2 + 0.42*x + 0.49

def draw_graph():
verts = []

for px in get_range(2, 8):
py = get_graph_y(px)
pz = 0
verts.append([px, py, pz])

edges = []
for i in range(len(verts)-1):
edges.append((i, i+1))

o = get_object("graph")
m = o.data
m.clear_geometry()
m.from_pydata(verts, edges, ())

draw_graph()


Take note that you can also easily plot this using Geometry Nodes. I'll update my answer with a GN solution later.

• ////////Python: Traceback (most recent call last): File "\Text", line 36, in <module> File "\Text", line 34, in draw_graph File "C:\Program Files\Blender Foundation\Blender 3.2\3.2\scripts\modules\bpy_types.py", line 564, in from_pydata self.vertices.foreach_set("co", tuple(chain.from_iterable(vertices))) TypeError: couldn't access the py sequence Aug 13 at 18:14
• I tried using "m.from_pydata(verts, (), ())" and the error doesnt change, but the code looks great! Aug 13 at 18:16
• oh sorry i wasnt able to test it but should be easy fix. i will fix it in 3 hours. its still 4AM now XD Oh but the pz=(0,0,0) is wrong. it should be pz=0. try that Aug 13 at 20:09
• Worked!!! Thank you! Aug 13 at 20:15
• cool no problem! :) Aug 14 at 6:54