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HDRI Skydome size mismatch Character Environment

AndySAndyS Posts: 1,434
in Daz Studio Discussion

Hi,

I just played around with some "dumroad" HDRIs. The first I noticed was a mismatch of the size of my character compared to the environment image produced by the HDRI Skydome.
As I moved the camera (Default Camera), the effect became even worse.

Now I systematically tried several scenarios.

  1. "Infinite Sphere"
    As I moved the camera away from my character, the size of the environment stayed constant, while the character "shrunk".
  2. "Infinite Sphere with Ground"
    Now the ground stayed constant (related to size and position) with the character. But all together "shrank" compared to the picture of the environment part of the dome.

These effects were independant whether choosing Infinite / Finite Sphere.
And they were independant setting "Draw Ground" ON / OFF.

For a better understanding I created short animations on youtube to demonstrate the effect.

Scenario 1:

Scenario 2:

Used DAZ Version: DAZ 4.9. General Release (4.9.2.70)
What is wrong?
If I create a scene with more characters / assets, I have to move the camera into a certain distance. So I'm getting a more and more dramatic size mismatch.
What to do about it?

 

Andy

Comments

  • MedzinMedzin Posts: 337

    you need a lower focal length with HDRI
    If FOV is narrow it will place a smaller segment of environment in the scene.
    A 35 mm focal length suits most of the scenes I do

     

  • AndySAndyS Posts: 1,434
    edited October 2016

    I don't know.

    Earlier, with version 4.8 I didn't notice this effect.
    It really looks, as if the camera is the center of the skydome. So if you turn the camera around your character, even the floor moves around. The character don't keep standing on the spot on the environment. That can't be correct.

    I expected the skydome being fixed to the world-coordinates.

    Even with 35mm camera, I get this deep crater if I move away with the camera a little.

    HDRI far Camera.jpg
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    Post edited by AndyS on
  • MedzinMedzin Posts: 337

    Where do these HDRI come from?

    They may not be mapped properly for DS

  • mjc1016mjc1016 Posts: 15,001

    As long as they are Width = 2x Height they are 'correct'.

    Probably, instead of infinite dome, switching to finite dome and scaling will be much more helpful.

    First image...infinite sphere.  Second image...finite sphere w/ground and dome radius set to 5.

    hdri_id.png
    640 x 640 - 626K
    hdri_fd_ground5.png
    640 x 640 - 817K
  • AndySAndyS Posts: 1,434

    Can't imagine, that it depend on the pictures.

    They are from this site and'd been promoted here in this forum.

  • mjc1016mjc1016 Posts: 15,001

    One big 'gotcha' in Studio...it's base unit is the centimeter.  Iray and many other things have as their base unit the meter.  Theoretically, the default settings for the infinite sphere should 'scale' close to correctly, but in practice, there are too many different set ups and assumptions made when the HDRIs are made to actually count on any 'automatic' scaling being accurate, especially when dealing with a unit conversion thrown in too.  Using the finite sphere (with ground) brings all the scaling under direct control.

  • AndySAndyS Posts: 1,434
    edited October 2016

    Sorry, but it doesn't work.

     

    Now I even tried the standard "DTHDR-RuinsB-500.hdr" with Infinite Dome and detected the same issue.

    What ever I try: As soon as I move the camera out of the "world Center", the picture gets distorted at the virtual corner between ground and sky (for draw ground = ON) or the characters / assets shrink (compared to the environment) for Ground = OFF.

    Post edited by AndyS on
  • Richard HaseltineRichard Haseltine Posts: 97,076
    AndyS said:

    What ever I try: As soon as I move the camera out of the "world Center", the picture gets distorted at the virtual corner between ground and sky (for draw ground = ON) or the characters / assets shrink (compared to the environment) for Ground = OFF.

    Surely that is to be expected - the HDRI is a sceen viewed from a particular point, moving more than a little away from that point will mean that you are no longer viewing the "objects" from the angle at which they are shown.

  • AndySAndyS Posts: 1,434

    But this is not a "Reality related Approach".

    Does (in the real world) the ground, background or sky stay the same size, if you change the focal length of your camera?

    What happens to the size of the environment, if you change the position of your camera from portrait to an overview of the whole scene?

    Shouldn't this be reflected working with DAZ ??

    IRay claims to be photorealistic. The observed behaviour is everything else - but not (photo)realistic !!

  • FishtalesFishtales Posts: 6,045

    HDRI aren't meant to be used as a scene as such, they are for lighting or backgrounds. To get them to work as scenes by moving the camera will only work on some, not all. Changing the Ground scale, up or down again depending on the HDRI, helps and the camera can be moved a little as can its Focal Length. As Richard points out the camera is in a fixed position when the image was taken so moving it causes distortion. You wont be able to look down as there isn't really a 'ground' to look at as the HDRI is on the inside of a sphere which travels below the subject which is standing on a virtual ground plane i.e. a shadow catcher.

  • AndySAndyS Posts: 1,434

    That really sucks.

    What you normally would expect: Even as the HDRI is only good for background, your characters / scene objects should stay on the same spot of the ground, when you change focal length or rotate the camera round the scene (even only a little) for some different points of view.

    As it is not.

    My conclusion: I only use some of the "cloud only" HDRIs or the sun-sky. All others can get covered in dust in your store.

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