Page 4 of 4 FirstFirst ... 234
Results 46 to 54 of 54

Thread: HDRI Exposure Control ?

  1. #46
    Registered User ianr's Avatar
    Join Date
    Oct 2006
    Location
    Chiltern Riviera
    Posts
    1,401
    Quote Originally Posted by scott.newman.ct View Post
    Thanks for taking the time to do the tests RPSchmidt.

    I notice your HDRI envirnoment got flipped somehow, so the render wont show quite the same results, but its still helpful to note the huge difference between "Raytrace+Backdrop" vs "Raytrace Only".

    For me, rendering with Glossy Reflections OFF is a realism killer for close up, hero objects. But it is very useful for getting rid of noise and bringing down anti aliasing times on smaller areas or simple objects that will stay further back from the camera.

    I was quite impressed with how well the despike filter actually worked in the end.

    Hopefully somebody from Newtek can get back to us at some point about what Asticles has pointed out about the ISBG sampling not working correctly.


    May I suggest ....You both should send in a report for a fix ?

  2. #47
    Quote Originally Posted by ianr View Post
    May I suggest ....You both should send in a report for a fix ?
    Dropped support a mail and got this response
    Click image for larger version. 

Name:	Screen Shot 2019-09-13 at 17.10.19.png 
Views:	36 
Size:	16.6 KB 
ID:	145973

    So it seems they are aware of it and its in the pipeline
    Scott

    Cape Town, South Africa
    http://www.youtube.com/user/independentvfx

  3. #48
    Registered User
    Join Date
    Apr 2016
    Location
    Barcelona, Spain
    Posts
    568
    Great!
    English is not my native language so please be patient.

    Salvador Ureņa
    http://urenasalvador.wixsite.com/portfolio

  4. #49
    Registered User
    Join Date
    May 2012
    Location
    Virginia
    Posts
    431
    I can definitely understand that for your work, you need glossy reflections. They do bring out roughness detail and other surface details you might not otherwise see.

    I mainly prefer them off because of the unexpected results I get under different lighting / HDRI situations and their habit of introducing noise.

    Oh, on the HDRI being flipped, it's because of my habit of putting -1 in the width (I had mentioned that earlier). It's one of those habits that's become so ingrained I just do it automatically.

    Great news that they have something in the works to do deal with this. There has long been a need for an exposure control for images, especially HDRIs. As you mentioned earlier, gamma for correction works, but it's definitely harsher and less elegant than exposure control.

    I will have to try the despike option myself. I haven't many issues with noise in a while, but it's nice to know another method of dealing with it.

    Best of luck, Scott and hope I didn't derail you too much with suggestions!

  5. #50
    Thanks again RPSchmidt! And to everyone else who took part in the chat. This forum is always so helpful!
    Scott

    Cape Town, South Africa
    http://www.youtube.com/user/independentvfx

  6. #51
    Most of it has already been said but perhaps misunderstood or rejected:

    If you use an Environment Light, you should use "Raytrace Only" in the Shading Model (as described in the manual). Otherwise you get twice as strong highlights. The other possibility would be to use "Raytrace + Bachdrop" and deactivate "Affect Specular" for the Environment Light.

    Since the Environment Light uses MIS samples I prefer first method. An HRDI can contain very bright pixels (e. g. the sun). If the surface is also very rough you need a lot of samples to get a clean rendering.

    In the image you can see that both methods lead to similar results and the combination of both is too bright. The differences can be explained by the fact that I still used far too few reflection samples. Thus the highlights are somewhat darker. Furthermore, the brightness of the reflection in LW is limited by "Reflection Limit" (here 5), the brightness of the Environment Light is not (unless you limit the whole dynamic range ). If the surface is less rough, you can see the effect better.

    The same applies to diffuse shading (sample backdrop in the GI settings). In this scene, however, only barely perceptible since the material is a conductor. In the image is also an example with a grey diffuse material.

    Click image for larger version. 

Name:	ueberblick_01.jpg 
Views:	32 
Size:	977.8 KB 
ID:	145997

    A prerequisite for correct results is of course a correct color space management.

    I hope this helps.
    ciao
    Thomas
    Web: www.dieleinwandhelden.com

    I use two pieces of the three-piece application with mocap module.

  7. #52
    Thanks for that Thomas

    You say that "The differences can be explained by the fact that I still used far too few reflection samples. Thus the highlights are somewhat darker." Does using less reflection samples really darken the result by that much? I think the real reason the highlights are so much darker is because if you inspect the specular indirect channel on Raytarce Only renders you will see there is almost no information in that channel so its not contributing to brightening the result.

    Also, whats strange is that if I switch Environment Light "Affect Specular" to OFF then my object doesnt render at all. It just renders black. EDIT: Ive tried this again, and it works/renders as long as I re-enable Glossy Reflactions.

    What I can say is that only the bottom row of images in your renders is the correct result visually for me, I think the raytrace only results are too dark for the scene.

    I would love to know more about the color space management youve mentioned. Do you know if that has been covered or discussed in another thread?
    Last edited by scott.newman.ct; 09-19-2019 at 03:28 AM.
    Scott

    Cape Town, South Africa
    http://www.youtube.com/user/independentvfx

  8. #53
    Quote Originally Posted by scott.newman.ct View Post
    ...You say that "The differences can be explained by the fact that I still used far too few reflection samples. Thus the highlights are somewhat darker." Does using less reflection samples really darken the result by that much? I think the real reason the highlights are so much darker is because if you inspect the specular indirect channel on Raytarce Only renders you will see there is almost no information in that channel so its not contributing to brightening the result...
    If you change the number of reflection samples you can clearly see the change in the brightness of the reflection. Strictly speaking, it is a combination of reflection samples and antialiasing.

    Name:  Reflection_Samples_01.gif
Views: 41
Size:  28.3 KB

    The diffuse example in my previous post clearly shows that the combination of both methods leads to too bright results: the material is a medium grey (R 127/G 127/B 127). In the bottom picture it looks like white. With metals this is more difficult to estimate, since we do not know which colour/brightness the material has.

    Comparing the buffers can be misleading here:
    The highlights that directly reflect the background can be found in the "Direct Specular" buffer, the indirectly reflected highlights can be found in the "Indirect Specular" buffer. Together they form the complete reflection. This is different when using "Raytrace + Backdrop" ("Affect Specular" OFF): all reflections is in the "Indirect Specular" buffer. "Direct Specular" buffer is empty.

    Click image for larger version. 

Name:	ueberblick_02.jpg 
Views:	17 
Size:	326.9 KB 
ID:	146006


    Quote Originally Posted by scott.newman.ct View Post
    ...What I can say is that only the bottom row of images in your renders is the correct result visually for me, I think the raytrace only results are too dark for the scene...
    Of course everyone can decide for himself what he likes best. I'm just describing the process as thought by Newtek. How realistic the renderer of LW is cannot be tested without laboratory conditions. For example, we don't know how correctly the HDRI is exposed (for example, the sun is not as bright as in reality). We don't know what color and brightness the metal actually has. And much more. . .

    If you use "Raytrace + Backdrop" you will go without the advantages of backdrop sampling of the Environment Light (MIS Sampling). You get a lot more noise.


    ciao
    Thomas
    Last edited by Thomas Leitner; 09-19-2019 at 10:25 AM.
    Web: www.dieleinwandhelden.com

    I use two pieces of the three-piece application with mocap module.

  9. #54
    Thanks Thomas

    You are absolutely right about the medium grey looking white. Good point!

    Wow, there really is a lot to learn. Its great that there are so many different approaches and options available.
    Scott

    Cape Town, South Africa
    http://www.youtube.com/user/independentvfx

Page 4 of 4 FirstFirst ... 234

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •