read mesh vertex color with python

Replies to This Discussion

Permalink Reply by Alessio Erioli on April 15, 2012 at 5:37pm

Hi Vince!!!

Color variable type is an hexadecimal number wich represents all 3 RGB components. If you use rhinoscriptsynthax you should extract them separately with rs.ColorRedValue(color), rs.ColorBlueValue(color), rs.ColorGreenValue(color). For example, here's a script that writes the Red component value on each of the mesh's points:

import rhinoscriptsyntax as rs

myMesh = rs.GetObject("select a mesh", rs.filter.mesh)
vCol = rs.MeshVertexColors(myMesh)
vPt = rs.MeshVertices(myMesh)

count = 0

for pt in vPt:
    co = vCol[count]
    rs.AddText(str(rs.ColorRedValue(co)),pt)
    count+= 1

try it out and let me know if this works. Oh, and... are you still in London?

Permalink Reply by Vincenzo Reale on April 16, 2012 at 2:25pm

Hi Alessio! Thanks for your answer, I am getting something better but still I don't understand how the data are stored inside MeshVertexColors (why when I print them I get not a list but the "Rhino.Display.ColorHSL object" thing) and while I can extract red green and blue I can't do it for hue luminance and saturation (there is no rs.ColorHueValue for example, while when I was using rhinoscript the hue was the first element of the list of rs.ColorRGBToHLS)

Here:

color = rs.MeshVertexColors(strObject)

while i <= len(arrFaces)-1:

      

      print color[i]

      red = rs.ColorRedValue(color[i])
      blue = rs.ColorBlueValue(color[i])
      green = rs.ColorGreenValue(color[i])

      print "red is", red
      print "blue is", blue
      print "green is", green

      hlsvalue = rs.ColorRGBToHLS([red,blue,green])

      print "hls is equal to " , hlsvalue

################

And what I get printed is

Color [A=255, R=55, G=55, B=55]
red is 55
blue is 55
green is 55

hls is equal to Rhino.Display.ColorHSL

So is there any way I can use the data stored inside hls variable???

Thanks again

V.

p.s. I'll be back in London on Thursday

Permalink Reply by Vincenzo Reale on April 16, 2012 at 4:05pm

Actually I overcome that problem using python conversion hls to rgb, but still there is some kind of problem that doesn't allow me to get the proper results.

The first cube was completely painted black, the second has just that white spot. But the vertex color is not assigned correctly (is there a point where I mess with the order?)

Any suggestions?

The script is :

import rhinoscriptsyntax as rs
import colorsys

rs.Command("_selmesh")
rs.Command("unweld 0")
rs.UnselectAllObjects

strObject = rs.GetObject("Select mesh", 32)
arrFaces = rs.MeshFaces(strObject)
color = rs.MeshVertexColors(strObject)

rs.EnableRedraw (False)

i = 0
arrFace = []

while i <= len(arrFaces)-3:

arrFace.append(arrFaces[i])
arrFace.append(arrFaces[i+1])
arrFace.append(arrFaces[i+2])
arrFace.append(arrFaces[i+3])

print(color[i])

red = rs.ColorRedValue(color[i])
blue = rs.ColorBlueValue(color[i])
green = rs.ColorGreenValue(color[i])

realcolor = colorsys.rgb_to_hls(red, green, blue)

rs.AddText(str(realcolor[1]),arrFaces[i],5000)

i = i + 4
arrFace = []

Attachments:

• cubes colors.3dm, 456 KB
• samplecolor test.py, 1 KB

Permalink Reply by Alessio Erioli on April 17, 2012 at 8:48am

Right now I cannot test your scripts but from what I read I have a question: why are you using mesh faces? Color is stored in vertices, and they are stored in a single dimension array. Faces then are a separate array of indices that point to the vertices array to say which is which in building the mesh faces.

To sample (and change) the mesh vertex colors you only need to sample its points, no need to use faces (or is there something I am missing in your steps?).

Regarding RGB to HLS right now I cannot make tests, maybe in the next days (or maybe someone else can help in the meantime).

See us in London then (I'll be there april 26-30, I'll message you in a while)!

Permalink Reply by Vincenzo Reale on April 19, 2012 at 4:34am

Hi again

I am using mesh faces because I wanted to average the vertices color in order to assign a "color property" to every face to influence a further tesselation. Using meshfaces on the unwelded mesh allows me to have for each faces the exact four vertices belonging to it, and then averaging their values. Somehow it seems that in my script I am loosing the correct connection between vertices and faces, so there should be another way to do it.

Any suggestions?

Regarding RGB to HLS using the colorsys.rgb_to_hls works well, so I just gave up the rhinoscriptsintax command, which seems to have some problem (it doesn't work as the help file says).

(see you next week then!)

Permalink Reply by Vincenzo Reale on April 20, 2012 at 3:28am

Ok, I solved this way if anybody is interested.

At first I used this set of commands:

strObject = rs.GetObject("Select mesh", 32)
arrFaces = rs.MeshFaces(strObject)
arrVertices = rs.MeshVertices(strObject)
arrColors = rs.MeshVertexColors(strObject)

than in a loop with the mesh corner points (arrpoints)

vertex = arrpoints[i]
indexColor = rs.PointArrayClosestPoint (arrVertices, vertex)
color = arrColors[indexColor]

So I could reference the correct color of every mesh corner

Than I just averaged them

cheers

Permalink Reply by adam on December 28, 2013 at 11:21pm

Hi Vincenzo,

I've gotten your script to work when using your mesh model, but for some reason, I got an error when I build my mesh by Meshbox. The message is following:

Message: index out of range: 0

Traceback:  line 26, in <module>, "C:\Users\Documents\Processing\Python Colors\samplecolortest.py"

I am using Rhino 5. Any idea what's going wrong? 

Also by the way, could you upload your latest script to let me have a try? Thanks!

Permalink Reply by adam on December 29, 2013 at 10:15am

I figured that out it, because the new meshbox has no color information on its vertex so I need first assign some colors onto those points. However, I still not quite follow your script on "than in a loop with the mesh corner points (arrpoints)", is there any information I missed?