On 2025-06-19 08:52 (-4), Chris R wrote:
> 
> Does the note about tentative new colors imply there is an update coming to
> RC3Metal soon?  I use that a lot...

That's the plan, anyway, except for the "soon" part.  The present
RC3Metal colors were eyeballed before I had a full appreciation of how
unreliable our eyeballs are at judging luminance.

I have a plan for measuring colors from digital photographs while taking
the environmental lighting into account, but there are still a couple of
problems.  My measurement of an orange brass object looks too yellow,
suggesting there is some flaw in my system.  And right now I have no
access to silver, gold, or the many variations of bronze.  Wikipedia has
a chart of gold alloy colors, but the chart is not color-calibrated.

Since the user can use any colors they wish, I have not prioritized
measuring new colors.  The colors I used for metalballs2b are:

  Aluminum         rgb <0.905, 0.915, 0.920>
  Brass            rgb <0.99, 0.78, 0.28>
  Golden brass     rgb <0.99, 0.70, 0.21>
  Yellow brass     rgb <0.99, 0.89, 0.38>
  Antique brass    variations of yellow brass
  Bronze           RC3M_C_BRONZE
  Chrome           rgb <0.550, 0.555, 0.555>
  Copper           rgb <0.99, 0.54, 0.38>
  Stainless steel  rgb 0.425

I have also been using rgb <0.99, 0.76, 0.33> and rgb <0.99, 0.92, 0.35>
for golds, based on SpectralRender, but I have no idea how they match up
to actual 24K gold and its alloys.

These colors are intended for assumed_gamma 1.  If you use some other
assumed_gamma, these colors are equivalent:

  Aluminum         srgb <0.9570, 0.9617, 0.9640>
  Brass            srgb <0.9956, 0.8962, 0.5657>
  Golden brass     srgb <0.9956, 0.8543, 0.4956>
  Yellow brass     srgb <0.9956, 0.9500, 0.6500>
  Bronze           srgb <0.6343, 0.5469, 0.3811>
  Chrome           srgb <0.7674, 0.7705, 0.7705>
  Copper           srgb <0.9956, 0.7611, 0.6500>
  Stainless steel  srgb <0.6836, 0.6836, 0.6836>
  Gold             srgb <0.9956, 0.8860, 0.6097>
  Light gold       srgb <0.9956, 0.9640, 0.6262>

The latest RC3Metal is 2.1-beta.1 on GitHub; it has a new macro for
adjusting the roughness of the specular highlights, but the suggested
colors are unchanged.

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