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When does turning off raytrace in UberSurface make any difference?

barbultbarbult Posts: 24,071
edited December 1969 in The Commons

I'm using DS 4.5.1.56 on a PC. I've read tips about turning off Occlusion and Raytrace in UberSurface settings of materials to speed up rendering, but I can't see that turning off Raytrace makes any difference in render time or appearance of the rendered image. I do see changes when turning off Occlusion. Under what circumstances does turning off Raytrace make a difference? Does it only affect certain lights? Does it only affect objects with trans maps? I just can't figure it out, in spite of trying lots of combinations of things. Please help.

Comments

  • frank0314frank0314 Posts: 13,936
    edited December 1969

    If there are a lot of transmaps then yes turning off raytrace will speed up the render

  • barbultbarbult Posts: 24,071
    edited December 1969

    Frank0314 said:
    If there are a lot of transmaps then yes turning off raytrace will speed up the render

    Does the Raytrace OFF only affect transmapped surfaces then? Or is that just where the most impact is? Shouldn't I see that there are no raytraced shadows in my image if I turn Raytrace OFF on all surfaces? I just don't see a difference. Does it matter what kind of lighting is used (standard DAZ lights with raytraced shadows, or UE with certain settings?)
  • KhoryKhory Posts: 3,854
    edited December 1969

    It is particularly apparent when your using a light with Ambient Occlusion. Not a huge deal if a small section of a render is hair or a tree. But if it has a large percentage of the space covered with hair or several trees then you will really notice the difference.

  • SpitSpit Posts: 2,342
    edited December 1969

    Studio has not always had AO available so we may forget how raytracing itself slowed down rendering on transparent surfaces. As for shadows if you turn raytracing off for a surface that won't affect shadows falling on it which are calculated by a light which has raytracing. That would be true for DAZ default lights. I'm not sure how it works with UberENV light though.

  • barbultbarbult Posts: 24,071
    edited December 1969

    Spit said:
    Studio has not always had AO available so we may forget how raytracing itself slowed down rendering on transparent surfaces. As for shadows if you turn raytracing off for a surface that won't affect shadows falling on it which are calculated by a light which has raytracing. That would be true for DAZ default lights. I'm not sure how it works with UberENV light though.


    You said it won't affect shadows falling on it, but does turning off raytrace stop that surface from casting shadows onto other surfaces?
  • Herald of FireHerald of Fire Posts: 3,504
    edited December 1969

    Only surfaces with shaders which specifically disable that feature will not cast shadows. Everything else casts a shadow. The pwSurface shader, for example, has a special switch which can prevent it from casting shadows, and also for preventing shadows being cast ON it.

  • barbultbarbult Posts: 24,071
    edited December 1969

    Khory said:
    It is particularly apparent when your using a light with Ambient Occlusion. Not a huge deal if a small section of a render is hair or a tree. But if it has a large percentage of the space covered with hair or several trees then you will really notice the difference.

    Khory, thank you for this insight. I was able to create a test setup so I could try various settings and see the results. I can now see what removing occlusion does and what removing raytrace does. Occlusion seems to make the biggest difference in my scene, both in appearance and time reduction. I used UberEnvironment Occlusion with soft shadows and one distant light with raytraced shadows. I rendered 1676 by 1453 with Max Ray Trace Depth 2. I applied UberHair to the hair to be able to turn occlusion and raytrace off.

    Occlusion On, Raytrace On = 1 hours 19 minutes 29.87 seconds
    Occlusion On, Raytrace Off = 1 hours 5 minutes 35.46 seconds
    Occlusion Off, Raytrace On = 33 minutes 37.76 seconds
    Occlusion Off, Raytrace Off = 28 minutes 48.62 seconds

    Occlusion_Raytrace_UberHair.jpg
    2000 x 2000 - 1M
  • KhoryKhory Posts: 3,854
    edited December 1969

    Occlusion seems to make the biggest difference in my scene, both in appearance and time reduction. I used UberEnvironment Occlusion with soft shadows and one distant light with raytraced shadows.

    I was just discussing this in a different thread earlier tonight. I think there are situations where the use of AO is more obvious. Renders that are "lighter" and on surfaces that are pale. It also depends on how the other shadows in the scene are falling. Sometimes it really shows, like your renders, and then there are times when I would swear on my life I can't see any difference it has made in the final render.

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