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Stray pixels in render.

SteveM17SteveM17 Posts: 985
edited December 1969 in New Users

My render has turned out as I wanted, except there are a few stray pixels (actually tiny squares). I've rendered in 3Delight, and this hasn't happened previously. Can anyone tell me what's gone wrong?

battlements.jpg
1860 x 867 - 879K

Comments

  • SteveM17SteveM17 Posts: 985
    edited December 1969

    I removed the flask from the swordsman's hip, and the stray pixels vanished. Strange! Anyone know why this simple prop would cause this (if it was indeed the cause) ?

  • SteveM17SteveM17 Posts: 985
    edited December 1969

    Ah, after some messing around, it seems the buckle on the flask had reflections activated, and this seemed to be causing the problem. Solved (so far)!

  • BlueSiriusBlueSirius Posts: 86
    edited December 1969

    Yes I have seen those before - often when I'm doing a quick render - I sort of figured it was a memory overflow so closed excess programs - but that was not the issue as it cropped up again on loading with very minimal memory useage.

    Not sure what the fix is except I have changed Render settings, replaced shaders with ones I know are for the render engine etc.

  • mjc1016mjc1016 Posts: 15,001
    edited December 1969

    Typically it is caused by using DeepShadowMap shadows...and there isn't a 'fix' other than playing with lighting/camera angles or just switching to raytraced sahdows.

    The cause is a deep seated problem with the shadowmap calculations and it goes all the way back to the first versions of Renderman and all Renderman compliant renderers.

  • SteveM17SteveM17 Posts: 985
    edited December 1969

    mjc1016 said:
    Typically it is caused by using DeepShadowMap shadows...and there isn't a 'fix' other than playing with lighting/camera angles or just switching to raytraced sahdows.

    The cause is a deep seated problem with the shadowmap calculations and it goes all the way back to the first versions of Renderman and all Renderman compliant renderers.

    I was using DeepShadowMap, and after I reduced the reflection strength on the buckle, helmet and sword (they were all full strength, or above the parameters) to zero the render worked as it should. I think having items that reflected each others reflections (if you get what I mean) caused the problem. I shall watch for this in future - luckily I've never needed to use reflections much, as I go for a comic book look rather than photoreal.

  • Herald of FireHerald of Fire Posts: 3,504
    edited December 1969

    I recommend using raytracing rather than deep shadow maps. It's not much different render wise, but the results are far better and you avoid little glitches like this one.

  • SteveM17SteveM17 Posts: 985
    edited December 1969

    HeraldOfFire said:
    I recommend using raytracing rather than deep shadow maps. It's not much different render wise, but the results are far better and you avoid little glitches like this one.

    Does it make the rendering time longer? If so, by how much?

  • mjc1016mjc1016 Posts: 15,001
    edited December 1969

    SteveM17 said:
    HeraldOfFire said:
    I recommend using raytracing rather than deep shadow maps. It's not much different render wise, but the results are far better and you avoid little glitches like this one.

    Does it make the rendering time longer? If so, by how much?

    Some time before build 11.0.130 of 3Delight, raytraced shadows, in many cases are faster than shadow mapped ones. 11.0.130 is the build included in Studio 4.8. This time saved is the time spent building the shadow map, in some cases, there is even more of a savings with raytraced.

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