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Thread: Extra Buffer nodes

  1. #661
    thanks,
    yes, that's what I meant, I played with tonemap, but still I would need to adjust white balance depending on where the camera is going I think..
    I was looking for something automatic, similar to a real camera, you can see adjust automatically depending on light input, I was
    wondering if something like that was possible with the node system,

    I usually did it before in post, but I was trying to get the LW render as close as possible as the final product, and just minor tweaks in post.
    It's just sometimes the post look can be very different than the LW render, especially when the camera goes in a dark area, and it's hard to know how
    it will look like when you texture things in LW too..
    Last edited by JML; 04-17-2013 at 08:19 AM.
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  2. #662
    obfuscated SDK hacker Lightwolf's Avatar
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    Quote Originally Posted by MSherak View Post
    Was thinking about this last night. Wonder if a node setup could check to see if the camera is being hit by a light (sunlight) or not.
    The problem is... the camera being hit by a light ray produces no change to an image. The camera only catches light that is reflected/refracted by surfaces.

    Cheers,
    Mike

  3. #663
    Quote Originally Posted by JML View Post
    thanks,
    yes, that's what I meant, I played with tonemap, but still I would need to adjust white balance depending on where the camera is going I think..
    I was looking for something automatic, similar to a real camera, you can see adjust automatically depending on light input, I was
    wondering if something like that was possible with the node system,

    I usually did it before in post, but I was trying to get the LW render as close as possible as the final product, and just minor tweaks in post.
    It's just sometimes the post look can be very different than the LW render, especially when the camera goes in a dark area, and it's hard to know how
    it will look like when you texture things in LW too..
    Maxwell render's camera does this brilliantly...
    But, you need at least 5 strong workstations minimum, to keep your sanity in place...
    AFAIK, all unbiased render engines handle automatic exposure, like real camera do... BUT...

    ...usually, this type of effect is something you DON'T want to happen when you're shooting live and avoid like hell, with careful planning on where the camera will go and how the scene is lit, aiming for a balanced exposure throughout the shot and increase/decrease it in post at will, where you have the most control.
    Even, for the cheap type of hand held documentary style of shooting (Cloverfield) you still want to handle exposure in post...

  4. #664
    a test with tonemap ON,


    Without tonemap,
    image 3 is darker, image 4 has almost no light,

    so it works well, but in the second image, the image especially the sky is blown out,
    so that's why I would need to adjust white balance ? , but doing that for 40 paths in LW, ouch.. I'll prefer to do that in post.

    so I don't know if something like 'auto-white balance' can be done with nodes, or it's just a visual thing that has to be done manually in AE

    Thanks
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  5. #665
    Quote Originally Posted by Gregg "T.Rex" View Post
    ...usually, this type of effect is something you DON'T want to happen when you're shooting live and avoid like hell, with careful planning on where the camera will go and how the scene is lit, aiming for a balanced exposure throughout the shot and increase/decrease it in post at will, where you have the most control.
    Even, for the cheap type of hand held documentary style of shooting (Cloverfield) you still want to handle exposure in post...
    what could help is having something like a 'exposure' setting in the camera property, so you can adjust the exposure per camera easily depending on what the camera is looking at..
    I saw you can adjust in the DP "linear tonemap" "use camera shutter' so I guess it could be done like that.. I'll have to play with it more
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  6. #666
    Quote Originally Posted by JML View Post
    what could help is having something like a 'exposure' setting in the camera property, so you can adjust the exposure per camera easily depending on what the camera is looking at..
    Yes, that would help quite a lot; that's what the VRay camera does well...
    But still; it won't adjust itself automatically for bright or dark areas; you'll still get overblown or extremely dark images, if there's no light balance throughout the shot...
    But, you can manually animate that value, so...

  7. #667
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    For an automatic exposure, the whole image buffer must be accessible
    for the current pixel being evaluated in the node editor,
    the Exposure node has no access to it, so the info of
    the maximum luminance is provided after the render.
    Tone Map node has access to the whole image buffer,
    so for the given parameter, tone mapping should follow
    the luminance changes in an animated sequence.

    I think that automatic exposure with real camera
    is not very good.
    In a movie the diaphragm is adjusted manually,
    to avoid a kind of 'pumping' in the image,
    or to preserve wanted overexposed or underexposed
    part of the scene. Not very confortable for the assistant
    operator when he is adjusting the focus and the diaphragm
    simultaneously, ..because a cloud is going to mask the sun..

    The Exposure node should be tested at different frames,
    for several strategic camera angles and/or light changes
    and then the node should be animated with these keys,
    with the Linear Tone Map node, real film situation
    can be simulated but still as a manual correction
    with the same work around.

    Denis.

  8. #668
    interesting, thanks for explaining.

    I'll play with LinearToneMap, and use camera settings to change brightness, using "Use camera F-stop"

    Thanks
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  9. #669
    Quote Originally Posted by JML View Post
    a test with tonemap ON,


    Without tonemap,
    image 3 is darker, image 4 has almost no light,

    so it works well, but in the second image, the image especially the sky is blown out,
    so that's why I would need to adjust white balance ? , but doing that for 40 paths in LW, ouch.. I'll prefer to do that in post.

    so I don't know if something like 'auto-white balance' can be done with nodes, or it's just a visual thing that has to be done manually in AE

    Thanks
    Adjusting the White Balance will change the color temperature, not the exposure of the image. Guess you might try by increasing the custom whitepoint in the Tonemap node. However, the problem you are having looks odd from the root, that is to say, the over-exposure itself.

    Take a look at your samples, you have a ELS of the building, then camera gets closer to a LS of the same building and your sky blow up, where there's not even sun! It has no sense... unless... your sky is not an environment map, but a flipped dome with the sky image mapped there... then, the first thing I can think of is you could have specularity applied to the dome and non-physically plausible specular values in the building as well. In such case it wouldn't be an exposure problem, but a shading problem.

    In case it's an exposure problem (and you use by chance AFX), you might want to try also Color Stabilizer filter. It can make a pretty good job automatically if there's no clipped highlights.



    Gerardo

  10. #670
    Quote Originally Posted by gerardstrada View Post
    Adjusting the White Balance will change the color temperature, not the exposure of the image. Guess you might try by increasing the custom whitepoint in the Tonemap node. However, the problem you are having looks odd from the root, that is to say, the over-exposure itself.

    Take a look at your samples, you have a ELS of the building, then camera gets closer to a LS of the same building and your sky blow up, where there's not even sun! It has no sense... unless... your sky is not an environment map, but a flipped dome with the sky image mapped there... then, the first thing I can think of is you could have specularity applied to the dome and non-physically plausible specular values in the building as well. In such case it wouldn't be an exposure problem, but a shading problem.

    In case it's an exposure problem (and you use by chance AFX), you might want to try also Color Stabilizer filter. It can make a pretty good job automatically if there's no clipped highlights.

    Gerardo
    the skydome is only for looks, It doesn't affect GI/rays, but there is a hidden lightdome that emit the light, maybe the tonemap is having issue with it.

    so for that project, I now used the F-stop of the camera to change the brightness using the "linear tonemap" node and it works great.
    (the only thing is that I have to turn on and off the DOF setting in the camera to change the Fstop value)
    most camera have the same F stop value, but when some camera looks at a dark area, I change the Fstop, and bright again ! really good.
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  11. #671
    A skydome seen by the camera and not affected by rays and by radiosity, may be still affected by the specularity component. If you turn Off the tonemap node and the over-exposure in the sky goes away, then it may be related with the tonemap node, but if you get the same situation or worst, then it's something else (a moving light or object perhaps). If we take a luminous dome and dolly-in the camera in the same direction, we'll see that it doesn't happen, it doesn't happen in reality neither. Can't say what's going on in that specific case without knowing the setup but understand the need to keep uniform luminance levels when camera goes from outdoors to indoors, or from a bright area to a shadowed one or vice versa. Glad you have found a solution! Linear Tonemap may be useful for simulating a physical camera. In case you want something like that, some pages behind there's a setup for emulating a photoreal camera, where changing the lens aperture, shutter speed and film speed will affect the DOF, motion blur, grain and exposure accordingly. Would be great to have an script doing this for multiple cameras - if such thing is even possible.

    But guess you don't want to mess with 3 parameters. In case you go with the Linear Tonemap (as an alternative of adjusting in the compositing package) and don't want to touch the F-stop (because it will change your DOF) you might try by changing the Sensitivity by using the envelope of a Scalar node.



    Gerardo

  12. #672
    thanks, that's a great photoreal setup, I saved it before to try to understand how it worked, the results are really good.
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  13. #673
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    I updated the windows versions of DP Filter,
    just added "Low Luminance" and "High Luminance" outputs in the Histogram node,
    as suggested by Gerardo,
    a quick auto-exposure can be made by connecting the "High Luminance"
    in the Exposure node,
    or make you own customized setup if you want to use
    the "Low Luminance".

    Denis.

  14. #674
    As Denis refers, the setup with the Exposure node is as simple as this:



    A custom-made setup could be something like this:



    Then, for this input sequence:



    This is the result:



    This is better than ColorStabilizer :)

    Thank you very much, Denis!



    Gerardo

  15. #675
    Thank you very much, I'll try that on Monday,
    that example looks really good !
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