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Blonde takes much longer to render than brunette?

wetcircuitwetcircuit Posts: 0
edited December 1969 in Carrara Discussion

In the "Carrara is messing with me" category comes this oddball: Same scene, all I did was drag the blonde image texture up out of the bump channel into the color channel and the blonde render takes significantly LONGER to render.... Despite the fact there are now fewer image maps in the scene... HUH?

Brunette pic takes 36sec to render (blonde map is in the bump channel, brunette map in the color channel)

Blonde pic takes 58sec to render (blonde map in the color channel, NOTHING in the bump channel)

*head hurts*
Carrara I love you, but... this makes no sense at all.

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Comments

  • wetcircuitwetcircuit Posts: 0
    edited December 1969

    Proof that blondes are high maintenance...? LOL

  • richard.chaos_91798ec102richard.chaos_91798ec102 Posts: 0
    edited December 1969

    Waiting for PUNCHLINE!

  • evilproducerevilproducer Posts: 9,050
    edited December 1969

    Was the blond map in the bump channel actually color or did you use a greyscale map with a color multiplier in the color channel? Or maybe the image map is a higher res?

  • WendyLuvsCatzWendyLuvsCatz Posts: 38,289
    edited December 1969

    what sort of lighting? blond hair would throw off more reflected light in sunlight or indirect lighting maybe.
    I don't know, never use fancy lighting myself.

  • wetcircuitwetcircuit Posts: 0
    edited December 1969

    It's shadow buffers... so I believe that is not "real" lighting at all but a geometry-based trick to create blob shadows...

    And both jpgs are the same pixel size (they are both original textures that came with the hair prop), and both are regular jpgs (saved inside the scene)... It seems like an oddly significant difference... Swapping the jpgs back and the rendertimes are consistent... The blonde jpg in the color channel takes longer....

    ...Unless the significant part is the EMPTY bump channel, taking LONGER to render...?

  • evilproducerevilproducer Posts: 9,050
    edited December 1969

    That would be odd. I would think no bump would be quicker.

    The real issue could be that blonds have more fun and Carrara just couldn't get around to rendering right away due to a party in the shader room.

  • wetcircuitwetcircuit Posts: 0
    edited December 1969

    evilproducer said:
    The real issue could be that blonds have more fun and Carrara just couldn't get around to rendering right away due to a party in the shader room.

    Riiiight? That's what I was thinking....

  • SockrateaseSockratease Posts: 813
    edited December 1969

    holly wetcircuit said:
    ...Unless the significant part is the EMPTY bump channel, taking LONGER to render...?

    I suspect that may be it. But have no idea why!

    To test, switch the 2 maps (blonde color & brunette bump) and see if the times are closer.

  • GFHELGFHEL Posts: 24
    edited December 1969

    evilproducer said:
    The real issue could be that blonds have more fun and Carrara just couldn't get around to rendering right away due to a party in the shader room.

    Thanks a lot for making me laugh! That's what I needed :))

    When I played around with Jai hair and applied just black and blonde presets, the same thing happened: black hair - 20 sec, blonde hair 35 sec.

    Looking at the render statistics, I found that black hair had 20,000 rays launched, blonde hair 35,000. So Wendy is right. If there is more to see, rendering takes longer.

    But we could look at it the other way round. Carrara renders economically. If there is less to see, it calculates fewer rays, speeding up the render where possible. In the end one reason more to love Carrara...

  • wetcircuitwetcircuit Posts: 0
    edited December 1969

    So weird.... So will a black cube render faster than a white cube?

  • GFHELGFHEL Posts: 24
    edited December 1969

    Seems to be more complicated.

    Actually, the cube I just rendered in black had a higher ray count than with the color set to white. The process seems not to be static either. Rendering the same scene several times resulted in slightly different values...

    Then I tried to force details by subdividing, twisting and exploding the cube. This didn't make much of a difference.

    But when I added Transparency or Alpha, things began to change. The same for Reflection. When either of them is turned on, the ray count is significantly different between light and dark colors.

    There must be some clever cutoff algorithm at work, which early recognizes that rays going through a transparent surface and hitting something black behind are not traced further. Or that a ray that is reflected from a black surface would not contribute to the appearance of the surface.

    That would explain why geometry based hair would render so differently: Lots of alpha masks...

  • GFHELGFHEL Posts: 24
    edited December 1969

    Nice guy, by the way :)

  • wetcircuitwetcircuit Posts: 0
    edited December 1969

    Thank you! He's M3...

    GFHEL said:

    But when I added Transparency or Alpha, things began to change. The same for Reflection. When either of them is turned on, the ray count is significantly different between light and dark colors.

    There must be some clever cutoff algorithm at work, which early recognizes that rays going through a transparent surface and hitting something black behind are not traced further. Or that a ray that is reflected from a black surface would not contribute to the appearance of the surface.

    That would explain why geometry based hair would render so differently: Lots of alpha masks...


    Hmmm, so interesting... This is actually what I was hoping was happening, but it seemed so far fetched that I thought it had to be an error or something....

    Thank you for the tests! From now on all my characters will have dark hair. LOL ;)

  • Kevin SandersonKevin Sanderson Posts: 1,643
    edited December 1969

    I remember back in the day of slower computers reading that blonde hair took more to render than dark and still often didn't look correct, so it was advised to use dark hair to save render times. Never timed it to see if it was true or not.

  • WendyLuvsCatzWendyLuvsCatz Posts: 38,289
    edited December 1969

    how many blonde video game characters do you see for that matter!

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