<![CDATA[Union on multi-color imported obj file lose colors]]>Hello, I'm trying to work with a multi-color obj file. It has 7 parts for a total of 312 triangles, and when I join them (with union), there are only 258 triangles which is explained by the fact that if the 7 parts had only 3 vertices polygons, the joined version had both 3 and 4 vertices polygons. This is not a big deal, but apparently as soon as a 4 vertices polygons appear, colors are lost for all remaining polygons. Is it a bug ? For the moment I can use a specific union function.
Capture d’écran de 2022-01-21 20-40-10.png

]]>https://openjscad.nodebb.com/topic/337/union-on-multi-color-imported-obj-file-lose-colorsRSS for NodeSat, 07 Mar 2026 12:28:30 GMTFri, 21 Jan 2022 20:01:27 GMT60<![CDATA[Reply to Union on multi-color imported obj file lose colors on Sun, 23 Jan 2022 09:08:53 GMT]]>@z3dev Sadly, lines already have a color (red for cuts, maroon for mountain fold and green for valley fold).
Capture d’écran de 2022-01-23 10-07-15.png

]]>https://openjscad.nodebb.com/post/1087https://openjscad.nodebb.com/post/1087Sun, 23 Jan 2022 09:08:53 GMT<![CDATA[Reply to Union on multi-color imported obj file lose colors on Sun, 23 Jan 2022 08:12:50 GMT]]>@gilboonet is it possible to add color to each of the unfolded pieces, i.e. add color to the lines?

]]>https://openjscad.nodebb.com/post/1085https://openjscad.nodebb.com/post/1085Sun, 23 Jan 2022 08:12:50 GMT<![CDATA[Reply to Union on multi-color imported obj file lose colors on Sun, 23 Jan 2022 05:46:44 GMT]]>@z3dev As you said, I'm keeping track of the colors from the original polygons and the unfolding works fine among those colors, but now my problem is that I didn't find a way to render the unfolded pieces with this color (imagine one of the colored 3d polygon on the volume unfolded with its color).

]]>https://openjscad.nodebb.com/post/1084https://openjscad.nodebb.com/post/1084Sun, 23 Jan 2022 05:46:44 GMT<![CDATA[Reply to Union on multi-color imported obj file lose colors on Sun, 23 Jan 2022 04:20:25 GMT]]>I’m not sure as the ability to track the original polygon colors will depend on the unfolding algorithm. Maybe the algorithm can keep a map to the original polygon, and use the original color when creating the 2D paths

]]>https://openjscad.nodebb.com/post/1083https://openjscad.nodebb.com/post/1083Sun, 23 Jan 2022 04:20:25 GMT<![CDATA[Reply to Union on multi-color imported obj file lose colors on Sun, 23 Jan 2022 04:15:31 GMT]]>The Boolean functions always return a new solid, without colors. This makes the results easy to understand.

For designs that want to use colors, the colors should be applied as the last step of a design. This allows designs to control the colors when exporting, e.g. exporting to OBJ with colors.

]]>https://openjscad.nodebb.com/post/1082https://openjscad.nodebb.com/post/1082Sun, 23 Jan 2022 04:15:31 GMT<![CDATA[Reply to Union on multi-color imported obj file lose colors on Sat, 22 Jan 2022 23:35:33 GMT]]>It only took :

let vf = require('./' + fileName)
var vf2 = vf[0]
if (vf.length > 1) {
	for (var i = 1; i < vf.length; i++){
		vf[i].polygons.forEach(function(p){ vf2.polygons.push(p) })
	}
}
var V = toPolyhedron(vf2)

But now as my script handles multi-color obj files and can unfold them as separate pieces, is there a way to render (in 2d) those pieces in color (if possible the same that is used on the 3d model) ? For the moment it's not easy to see which unfolded piece correspond a 3d piece.
capture DEPLIEUR COULEURS.png

]]>https://openjscad.nodebb.com/post/1081https://openjscad.nodebb.com/post/1081Sat, 22 Jan 2022 23:35:33 GMT