Incorrect RGB color representation


#1

Hello,

I’m often using SketchUp for 2D stuff, like simple logo or layout. I draw it, then I open “Materials” window, create new material for each color (using particular RGB values) and apply them on faces by Paint Bucket.

I want to point out at this point, that I tried everything I was able to google, like “use sun for shading” with sliders to max/min, with no luck.

So, my problem is, when I export it to PNG, colors there don’t match entered RGB values of used materials. I understand it’s probably affected by some global light or shading, but when I create PNG texture for each color (so instead of RGB I use texture image), RGB in final PNG is correct. In fact, it’s not only on PNG, but it’s in the app (“editor”) as well.

In the following screenshot, on the left is material with RGB (204,102,102), on the right is material with Texture (filled with the same RGB). You can notice that the thumbnail in Materials window have a correct RGB, but when applied, it changes to 245,122,122. I also used the suggested “Use sun for shading” trick, with the same result.

It’s not very efficient to have a PNG for each color I want to use :smiley: So, please, is there a way how to use RGB color fill without distortion?

Many thanks.


#2

RGB is not the only color model (= way to describe colors). A common one is sRGB which is able to represent some more colors of human perception. PNG images seem to use most times sRGB, and if I’m not mistaken that’s what OpenGL uses.
It could be that SketchUp does not treat plain colors as sRGB and also does no (or no precise) conversion.

You will also often notice color mismatches when using jpeg and png textures of same color but different color profile side by side.


#3

It is a bit of hit and miss with the Light and Dark sliders. When I last tried, it looked flattest when the Dark slider was at about 80%, but there is no sure way of getting it scientifically right. If your goal is to get a range of flat colour samples, why not use an image editor?

Anssi


#4

No, my main goal is to export a colored 2D image from SketchUp to PNG (I understand I may mis-use SketchUp for this scenerio). Like a logo. Or a flag. Flag is a good example. If you want to recreate a flag of a country, you can google what RGB colors it uses. Then you draw the flag in SketchUp and apply those colors. But when you export the finished colored flag as PNG, colors will be different, with different RGB, than you entered in the Material window in SketchUp. The only way to match them it is to create - like you wrote - flat color samples in an image editor (I use Paint.NET) and apply them in SketchUp as textures.

Of course, you can export the flag to PNG and fix colors in an image editor on that PNG, but it’s a double work and IMO it should be done in SketchUp. I can imagine a setting, where all shading is turned off and even in a 3D model all faces have the exact color, as defined by RGB values.

My biggest issue is that the “solid color texture workaround” works like a charm whilst regular native colors are different in the model, than presented in color picker.


#5

I must admit I’m a bit confused as to why you would use a 3d modelling program to make 2d images.
So often people complain that they can’t do this or that like they can in photoshop or similar and you are kinda going the other way.
If you want 2d rgb accurate graphics use a 2d graphic editor.


#6

Using a 3d modeler comes with all the implications of the third dimension: depth, normals and their influence on shading. This is like choosing a camera to take a photo of an art lexicon, instead of using a scanner.

Many people discover SketchUp as their first vector drawing application (that draws straight lines instead of pixelated ones!). But SketchUp is a really bad vector drawing app because it is focused on polygon modeling with segmented lines (and thus it has no native bezier curves etc.). Learn to use a vector drawing app, and choose the right tool for the right task.


#7

Thanks Anssi, you’re right. Dark at 80 %, Light at 100 %. It didn’t occurred to me that Time and Date are taken into account, so it works as expected with Jan 1 at Noon UTC.


#8

To do 2D vector graphics, the best free option in my opinion is Inkscape. It has the advantage over SketchUp in that its curves are real ones and not segmented, as SketchUp has to use geometry that is compatible with 3D models using flat faces.

Anssi


#9

Thank you for your suggestion, let me explain myself. I know Inkscape quite a long time, but I never got use to it; I’m abusing SketchUp for 2D because of it’s usability, I’m quite “productive” in it and it’s more comprehensible to me, than Inkscape (which also feels slow and clumsy).

To be honest, last time I did some SVG in Inkscape I ended up writing the XML by myself, because in Inkscape I wasn’t able to achieve exactly what I wanted (also my code was about half size). Inkscape offers so many options and choices, so a lot of things I use often is “too far away” (buried in GUI). Also, I often use the “snap to a midpoint” in SketchUp, which I wasn’t able to find in Inkscape, or easy drawing by entering numeric lengths.

In a short way - for me, drawing in SketchUp feels like fun, drawing in Inkscape feels like work :smiley: