Getting an exact RGB value

[RErender]

When I use this method, I get numbers over 255.
is something wrong in formula? or what am I doing wrong?

Color I want see is medium gray: rgb (128,128,12
Color I get: rgb (224,233,233)

so
r: 224x255/128 = 446.25
g: 233x255/128 = 464.179

As i understand it, the formula works to adjust the hue not the exposure, so in your example you'd need to adjust the exposure to be closer in range then use the formula along with the color balance to remove the sun/sky tint. Not sure if the iso formula would work to get you in range first, and I'm too lazy to try it right now. heh

[giraffe]

or maybe 255 is not up pn the fraction but down ?

[DONGHU_SENIOR]

Ask

I had to deal with this recently, so I thought it may be useful.

The problem:

We want to obtain an exact RGB value for some (small) surface in our image. Let's say the RGB value is xr, xg, xb which range from 0 to 255.

The solution:

1) Render the scene in any way you want with any settings you want, but make sure you use Linear color mapping with 1.0 for both Bright and Dark multipliers and the "Clamp output" option is off, and you are using the V-Ray camera "Exposure" setting. It would also be handy if you render to the V-Ray VFB.

2) Measure the RGB value at the pixel you need to match. If the values are, let's say (pr, pg, pb) again from 0 to 255, adjust the V-Ray camera "White balance" to be (pr*255/xr, pg*255/xg, pb*255/xb) and multiply the camera ISO setting by (xr+xg+xb)/(pr+pg+pb).

Note that this works only for Linear color mapping. In principle it can be done for any color mapping, but the numbers are hard to find by hand.

Best regards,
Vlado

s What are representatives?
p What are representatives?

[glorybound]

PR

Proposed
Real

Or that is how I saw it.

[duke2]

"Let x equal the windmill"

Excellent.

http://www.youtube.com/watch?v=k72awYjfGfk

[chicoone]

Just make sure that desired base colors are more more saturated than the measured values.
Example: With an ISO of 100 R G B
Measured: 128 128 128
Desired 255 255 255
WB= 128 128 128 (Same as measured)
New ISO= 199.2188
Makes sense?

For all colors less saturated, the WB=measured Colors and leave the ISO alone; I think..., maybe not!

[jackieteh]

Is auto white balance in V-Ray 6 do all this job automatically?