| Author |
Message |
    
Tom Djajadiningrat
Junior Member
Username: Pobo
Post Number: 27
Registered: 11-2003
| | Posted on Friday, April 11, 2008 - 08:22 am: | 
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I'm trying to render a product with HDRI lighting and ambient occlusion. I'm pretty happy with the lighting on the object itself, but the shadows look a bit messy to me. I'm using the 'empty kitchen' spherical map from the LightWorks starter collection, the number of HDRI samples is already at 1000, the number of AO rays is already at 196. The ground plane does not cast shadows.
What is the trick?
The lighting on the dune buggy example (Figure 6.1.6.12) in the manual looks pretty good to me, though perhaps a little soft. ZWeb, any chance of sharing the settings for this rendering?
Any help greatly appreciated.
Tom
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support@formZ.com
Moderator
Username: Tech
Post Number: 4878
Registered: 04-2001
| | Posted on Friday, April 11, 2008 - 08:48 am: |
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Tom,
With the settings that you show, your shadows should be nice and smooth. EDIT -- see next post... Therefore, please send your FMZ file to us so we can see why you would get this result. (We have the HDRI image, so you don't need to send that...)
We can't tell if your Scene Size is appropriate, so do check to make sure that this size is set correctly. (It should be the physical width of your image, which would be approximately 50% larger than your product.)
We can see that you are probably getting nothing from Ambient Occlusion because you only have 10% Ambient and no Additional Contrast. (We would recommend turning off AO and rendering again so you can see the difference.) Then turn off the Environment Light, increase Ambient to ~60%, and test rendering again. Finally, reduce Ambient to ~40%, cut your HDRI Intensity about in half, and render once more. Then compare all these results.
Both Atmospheric Light and Environment lights are in a class of lights that are termed "Dome Lights." (As a general rule, never use more than one Dome Light in a project -- not that we think you are...)
Final Gather rendering contains optimizations that can actually make Dome Lights more efficient (ie, render faster) than without Final Gather, and many fewer samples are required. You might try enabling Final Gather and reducing your HDRI Samples to 100 - 200 to see if this gives you better results.
Once we see your file, we should be able to answer your original question.
ZWebTech Support |
support@formZ.com
Moderator
Username: Tech
Post Number: 4879
Registered: 04-2001
| | Posted on Friday, April 11, 2008 - 08:55 am: |
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Tom,
After thinking for another moment, it is possible that the number of Environment Light Samples may not be enough for this specific image. This is because the Kitchen Image is generally dark and only has a few bright areas. Therefore you might need to have a higher number of samples to smooth out the light that comes from these isolated areas. Instead of doing this, we would probably recommend just using a different HDRI image (one that has a little more even illumination). Does this help?
(Our other comments should still be valid, so do still try these suggestions...)
ZWebTech Support |
Tom Djajadiningrat
Junior Member
Username: Pobo
Post Number: 30
Registered: 11-2003
| | Posted on Monday, April 14, 2008 - 05:43 pm: |
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ZWeb,
I tried another HDR image called 'harbour' instead of the 'empty kitchen' one and indeed most of the shadow problem is largely gone at 5000 samples (there is still a little bit of banding left but I guess that will be gone at 10000 samples or so). I must say that I actually liked the lighting on the object itself better with the 'empty kitchen' HDRI than with the 'harbour' HDRI: it seems more contrasty and less flat to me.
Here's the difference:
---
Image 1:
HDRI = 'kitchen'
env. light = 500 lumen
samples = 1000
amb. light = 0
AO = off
---
Image 2:
HDRI = 'harbour'
env. light = 200 lumen
samples = 1000
amb. light = 0
AO = off.
---
Image 3:
HDRI = 'harbour'
env. light = 250 lumen
samples = 5000
amb. light = 0
AO = off.
---
OK, reading your reply and having re-read the manual, it is slowly dawning on me that my conceptual understanding of AO was completely off.
My new understanding is (please tell me if I'm wrong)
* to use AO, there should be sufficient ambient light in the scene. If there is no ambient light or very little ambient light (10%), AO is not going to work.
* rendering with no ambient light and 60% ambient light is to find the extremes for AO to work between: the brightest fully exposed surfaces vs. the darkest nooks and crannies.
* AO and HDRI are two separate things which need not go together.
* one can use AO and HDRI together
* one shouldn't use Atmospheric Lights and AO together
Things I still do not understand:
* if I use HDRI without using AO, is it better not to use ambient light at all? Or does it still makes sense to have a default of 10% ambient light?
* I thought that it made sense to use an interior HDRI image map for product design renderings (that's why I chose the 'empty kitchen' image) and that somehow using an exterior image map might look a little strange on a product supposedly set indoors.
* Can one tell beforehand what kind of image an HDRI map will result in? Say I want a contrasty image or dark shadows, what characteristics in an HDRI map should I look for?
Tom |
support@formZ.com
Moderator
Username: Tech
Post Number: 4920
Registered: 04-2001
| | Posted on Tuesday, April 15, 2008 - 08:38 am: |
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Tom,
Your original image file has a distinct bright spot that is generating the fairly direct shadow(s) -- (and without using a lot of Samples, this kitchen image will produce multiple shadows). The other images that you are using are much more uniform, and as such you may want to add a Cone Light that casts Soft Shadows to supplement these. The other HDRI images that you have also have a lot of color to them, in which case you probably want to reduce the Color Factor from within the light's parameters so that this does not overwhelm your rendering.
AO will remove ambient light from a scene where objects are adjacent to other objects. If there is no ambient to remove, you will see little (no) difference in the rendering unless you increase the Additional Contrast option. Also, Z-Buffer rendering with AO can produce artifacts, so always use Raytrace (at least for a final rendering).
One quick way to use Ambient Occlusion is to first illuminate your object with only ambient light so that the side away from the light source receives sufficient light (perhaps using ~30 - 60%). Then add the direct light and adjust its intensity to your liking (in conjunction with the ambient). Then set the right Scene Size, set Ambient Quality to 1, and adjust the other values to your liking. Once you have it as you would like, you can then increase the Quality to 2 or 3 until the artifacts disappear.
AO and HDRI lighting are completely different. AO removes light from a scene, while HDRI adds light.
HDRI and Atmospheric Lighting are very similar -- the former distributes light from a sky dome based on an image, while the latter distributes light from a sky dome based on the location of the direct component of the light. AO can be used with either HDRI or Atmospheric Light, but since HDRI and Atmospheric lighting are so similar (and effectively create a lot of light sources for each one), you can use either HDRI or Atmospheric lighting if you want, but you should not use both at the same time.
AO is a fairly fast calculation. Therefore, this is probably the first option that you should use to increase the quality of your renderings. If you then want to add HDRI, that is fine. You might want to try turning off the shadow casting of the HDRI light (so you need fewer samples) and just allow the AO to create the "shadow."
The more the contrast in the brightness in an HDRI Image, the more the contrast it will produce in a rendering. Try making a very simple scene with a few primitive objects on a plane, and then render with only HDRI with ~50 - 100 samples. Change the Image and see how it affects your scene. Note also that a relatively dark HDRI image will require a higher intensity to produce the same brightness in a scene as a brighter HDRI image.
Final Gather rendering contains optimizations that can actually make Dome Lights more efficient (ie, render faster) than without Final Gather, and many fewer samples are required. You might try enabling Final Gather and reducing your HDRI Samples to 100 - 200 to see if this gives you better results.
Once we see your file, we should be able to answer your original question.
ZWebTech Support |
Tom Djajadiningrat
Junior Member
Username: Pobo
Post Number: 32
Registered: 11-2003
| | Posted on Tuesday, April 15, 2008 - 05:52 pm: |
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Zweb, many thanks for taking the time for that elaborate explanation. It definitely improves my understanding.
One of things I like about HDRI as opposed to Atmospheric lighting is that there is so little set-up involved: no positioning of light sources and only one intensity.
I have dropped my file 'Djajadiningrat_AO_HDRI.fmz' in the FTP dropbox.
Tom |
support@formZ.com
Moderator
Username: Tech
Post Number: 4928
Registered: 04-2001
| | Posted on Wednesday, April 16, 2008 - 09:35 am: |
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Tom,
The file on our FTP appears to be corrupted. Could you ZIP it and upload it again?
Thanks in advance,
ZWebTech Support |
Tom Djajadiningrat
Junior Member
Username: Pobo
Post Number: 33
Registered: 11-2003
| | Posted on Wednesday, April 16, 2008 - 09:55 am: |
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Zweb,
I've uploaded the ZIPped file: 'Djajadiningrat_AO_HDRI.zip'.
Hope it works now.
Regards,
Tom |
support@formZ.com
Moderator
Username: Tech
Post Number: 4933
Registered: 04-2001
| | Posted on Wednesday, April 16, 2008 - 05:33 pm: |
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Hi Tom,
We have a number of suggestions for you. Do you mind if we post your file back here?
ZWebTech Support |
Tom Djajadiningrat
Junior Member
Username: Pobo
Post Number: 34
Registered: 11-2003
| | Posted on Thursday, April 17, 2008 - 04:10 am: |
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That's fine, it has already been stripped of anything sensitive.
To |
support@formZ.com
Moderator
Username: Tech
Post Number: 4935
Registered: 04-2001
| | Posted on Thursday, April 17, 2008 - 10:07 am: |
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Hi Tom,
We did not have a lot of time to work with this, but as you can see from the attached file, we can fix the shadows and get very similar renderings in much less time. (And if you tweak the parameters further, get even better quality...)
Once you open this file, go to the Palettes Menu and open the Scenes Palette (if you do not have this open already). This coordinates lights, render options, etc so that you can switch between different render options (which are noted in the Scene Names).
The only thing that Scenes do not do (currently) is to change the Ambient Light, so after you select a Scene, adjust the Ambient Light setting as noted in the name.
Also, after selecting the Scene, immediately deselect it to prevent making unwanted changes to the other settings. (A selected Scene will automatically record any changes that you make...)
In addition to adjusting the lighting and the render options, we also added some specular reflection to your orange surface style.
And if others want to render this file with the same HDRI image file, just do a Google Search for the name...
Hope this helps you, and others! 
ZWebTech Support |
Tom Djajadiningrat
Junior Member
Username: Pobo
Post Number: 35
Registered: 11-2003
| | Posted on Thursday, April 17, 2008 - 04:44 pm: |
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ZWeb,
Thank you so much for your fantastic support. Simply unrivalled.
The Scenes palette is a completely new discovery for me and the different lighting settings definitely something to chew on.
Thanks again.
Tom |
Robert Woodruff
Senior Member
Username: Setz
Post Number: 173
Registered: 09-2006
| | Posted on Friday, April 18, 2008 - 10:02 am: |
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Adding the noise option to the AO really makes a big difference in killing the shadow banding . Thanks for sharing the file,
r. |
support@formZ.com
Moderator
Username: Tech
Post Number: 4959
Registered: 04-2001
| | Posted on Monday, April 21, 2008 - 09:06 am: |
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Robert,
Yes, this can allow you to generate the rendering faster. Of course you could also turn off the noise and increase the number of rays...
ZWebTech Support |
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