• Maxon Cinema 4D

  physically accurate light colours

  Posted by Greg Serafin on March 1, 2008 at 7:26 am

  Hi all,
  I promised a fellow teacher to produce a simple animation explaining the mixing of RGB lights into pure white colour (C4D10).
  I created 3 spotlights with pure R, G and B light colour, pointing at a single target Null and hit the wall.

  If I position all those lights at the same spot I get a pure white light as expected.
  However when I move the lights to sit at 120 deg apart (on a triangle) pointing at a white polygon, I can see the three primary colours (overlapping ellipses), nice secondary colours, but the overalp of all three in NOT WHITE?!?!?!
  I am getting a “white-ish” shape, but there is a noticeable colouration – red in opposite the red light, green opposite the green etc.

  Is this a bug in the rendering engine or is there a setting I should be aware of to fix this?

  Brian Jones replied 18 years, 2 months ago 2 Members · 3 Replies
• 3 Replies

• 

  Brian Jones

  March 1, 2008 at 5:19 pm

  Assuming you have falloff turned off or are within it’s inside radius and have the spot lights ‘Use Inner’ turned off (Details tab) or have a non zero Inner Angle…

  You have a number choices
  1 – crank the intensity of the lights to over 100 (200 works)

  2 – play with the material on the plane/floor/wall
  -take the intensity of the Color channel of the material to over 100 (200 works)
  -in the material’s Specular tab increase height/Falloff to 100 Width to whatever works for you.
  -in the Illumination tab of the material experiment with Blinn or Oren-Nayar instead of just Phong they are more accurate(?) and will give different results in combination with Specular changes.
• 

  Greg Serafin

  March 2, 2008 at 9:48 am

  Thanks for your reply.

  I’ll try the suggested solutions. The only issue I see with them is that they require “burning” the white area, the problem there may be that we wanted to show the RGB lighting hitting different object and they may become “flat” where burnt…

  Will give it a go anyway.
• 

  Brian Jones

  March 2, 2008 at 1:46 pm

  I don’t think “burning” is the right word. You don’t have to increase anything beyond 100% (that’s just the easy way) – you just need 100% specular and ‘not phong’. Go to go but quickly but remember nothing in nature is white – and when this experiment is done in the classroom do you think the lights are perfect Red, Green, Blue – not likely. They almost certainly have a mixture that is predominant in one color but in 3D we can have perfect lights of only one color so it needs a perfect specular to get it all to bounce back to us as white.

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