Inaccurate RGB Color Output


#1

Hello all, I am having a major issue with Sketchup changing the output RGB color value from what the input RGB values are listed as in the material editor.

So here is what is going on. I have loaded this jpg image of a color palette into Sketchup. Then I create a material and use the on screen color picker to try and grab a color off the image to use as the color on a face. Now with all lighting and shadows disabled, it still outputs the wrong values. For instance with this green color “Classroom Zone 1”, the input values in sketchup are correct RGB (96,184,142), but the output value when taken to Photoshop WITH ALL SUN AND SHADOWS OFF is RGB (115,221,170).

Now to further complicate the issue, some colors are pretty close to the one picked from the color palette when using the on screen color picker tool, where as some (such as the green color in the example), is way way off. It seems almost random how it changes the color.

I can understand where the color value would change when viewed with lighting and shadows being adjusted, but with just a flat image from a top down view I don’t understand why I can’t get the color to match. If anyone can let me know if there is anything I can do I’d really really appreciate it.


#2

Even with shadows (the sun) turned off, SU renders objects on screen using shaded surfaces to help with 3D visualization. Consequently, a colored face seldom appears on your model as the exact RGB value as its color chip in the Material browser. Clearly, if colors appeared identically on screen no matter how they were oriented in space, the objects on screen would have an overall flat, 2D appearance, not what most people are expecting from a 3D model.

I will leave it for you to reflect upon whether you are imposing a sort of 2D mindset on your 3D model (to its detriment), and whether you might find a more effective method to key the model to the legend than color-coding. My opinion at this point is probably obvious.

That said, it is possible to defeat SU’s use of shade to differentiate like-colored surfaces facing different directions, but only at the expense of degrading the qiuality of the 3D presentation.

In the Shadows dialog, make sure shadows are off (the button in the upper left corner). Check the box captioned “Use sun for shading.” Then fiddle with the light and dark sliders until the effects of shading are essentially no longer in evidence. This generally happens when both sliders are at around 80 or above. Experiment with this until you’re satisfied with the result.

-Gully


#3

This is the general consensus I am receiving on the subject. To be honest it is just really painful that there isn’t like a plugin that can compensate or even something like a curve adjustment I can apply in Photoshop. The problem is that if you apply a color adjustment in Photoshop you have to mask out and adjust each color. To further complicate the issue and why I’m trying to come up with any kind of easier solution is that we have several school systems we cater to and each school system has a different standard based on their history. So I’m given the RGB values when we get a new school system to match which is a very very painstaking process to do just via Photoshop and Sketchup. The process for that is print screening the Sketchup models and comparing the resulting RGB value to the output and then tweaking the RGB inputs back in Sketchup to match what the output should be.

Also the output color values vary so much from one color to the next. The only solution I’ve developed so far is quite grueling still considering the hundreds of schools that we have. My current method involves exporting a vector graphic of the floorplan and then adjusting the color values in Illustrator using the eye dropper tool. Then I export the shadows to a png file and have to overlay that on the color adjusted vector graphic. It results in three files just to achieve the final png file (and obviously a lot more work than just exporting from Sketchup to a png file with a transparent background).

I have played with the use of the sun only and the light and dark settings which again will get a lot of the colors close, not perfect but close, but then it messes up other colors so that is not really an option for me unfortunately.

I was just wondering if some Photoshop guru or plugin creator had a magic way to compensate for this with either a Sketchup plugin, or Photoshop curve they created or came across.


#4

When your success depends on magic, I’d say you took a wrong turn somewhere.

-Gully


#5

Yeah I know, but at the same time when a program provides a place to enter RGB values one would expect that color to be output without having to involve magic.


#6

It’s like buying paint at the Home Depot (or pick your paint store). Thinking you can simply match RGB values without respect to lighting and geometry is a rather simplistic approach.

-Gully


#7

can you post an example model?

maybe you could create a true color ‘Style’ set that you export to Layout as scenes, i.e. only shadows as raster with another as vector lines with flat colors…

maybe…

john