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  1. #221
    Is there some really good examples of what Cycles is currently capable of? I have seen http://chocofur.com and he has some fairly real looking interiors. Just would like to see some more stuff. Thanks



  2. #222
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    Um, I don't really see the problem with your tests. Each image renders correctly, the one with the correct portal placement has the lowest amount of noise. That's exactly how it's supposed to work.



  3. #223
    Originally Posted by joshbailey View Post

    Had a go at one of the scenes you linked.... could use a little work but 20 more minutes of work and it can be super close to the image. Render time was 400 samples in 6 min. Cycles is noice :3.

    This is somewhat off topic because it doesnt have light portals in it :|




  4. #224
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    Originally Posted by lukasstockner97 View Post
    Um, I don't really see the problem with your tests. Each image renders correctly, the one with the correct portal placement has the lowest amount of noise. That's exactly how it's supposed to work.
    Yes, from point of view of noise it is allright. What I don't understand is the scene luminosity, that I expect changes when portal is reduced or hidden, and instead it doesn't change.



  5. #225
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    Why sbould the luminosity change? Cycles is a physically based renderer, and there is only one physically correct solution. Portals help to find it faster, but it always is the same. In fact, if you find a scene which converges to a different result with and without portals, that'd be a bug.

    This also answers the "Can Cycles render something like this": Assuming the other renderer is physically correct as well, it can.



  6. #226
    Originally Posted by LordOdin View Post
    Had a go at one of the scenes you linked.... could use a little work but 20 more minutes of work and it can be super close to the image. Render time was 400 samples in 6 min. Cycles is noice :3.
    Tidy work there! thanks for the time you spent doing that. As a nooby, it is pleasing to see results that inspire me replicated in cycles.



  7. #227
    Member Lell's Avatar
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    Originally Posted by lukasstockner97 View Post
    Why sbould the luminosity change? Cycles is a physically based renderer, and there is only one physically correct solution. Portals help to find it faster, but it always is the same. In fact, if you find a scene which converges to a different result with and without portals, that'd be a bug.

    This also answers the "Can Cycles render something like this": Assuming the other renderer is physically correct as well, it can.
    Another thing I would like to know by the author is why Cycles casts random rays to find the environment when there are portals in scene. If Cycles wouldn't do, reudcing the protal dimension should lead to a darker scene. That why I expect darker scene with smaller portal or with portal placed in front of walls.



  8. #228
    Originally Posted by LordOdin View Post
    Render time was 400 samples...

    Hi LordOdin,

    with 400 Samples!!!

    How did you do that???

    A special Material for the walls?

    I tried several indoors (with and without portals) and I have sometimes over 1000 samples... and still noise.



  9. #229
    Cross posting from here.

    Why are Blender's portals based on Area lamps? Every other soft on the planet has it as a material to be applied to a mesh. The work flow for portals in other soft is to select your window mesh, dupe it, and assign a portal material - job done.


    In Blender, you have to now go to the menu, create an area lamp, fudge about positioning it correctly so that it matches up with the geometry of the window, then go to another menu to tell it that it isn't an area light but a portal.


    Imagine the wasted rays of doing an old cathedral with arched windows with this method. Secondly, think of how much longer it's going to take to manually position all those area lights on all those windows. If you had material portals, your workflow would be to go into edit mode, select all faces with the window material, dupe it, separate it into it's own object, then assign a portal material - MUCH MUCH MUCH FASTER.



  10. #230
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    Originally Posted by Tea_Monster View Post
    Cross posting from here.

    Why are Blender's portals based on Area lamps? Every other soft on the planet has it as a material to be applied to a mesh. The work flow for portals in other soft is to select your window mesh, dupe it, and assign a portal material - job done.


    In Blender, you have to now go to the menu, create an area lamp, fudge about positioning it correctly so that it matches up with the geometry of the window, then go to another menu to tell it that it isn't an area light but a portal.


    Imagine the wasted rays of doing an old cathedral with arched windows with this method. Secondly, think of how much longer it's going to take to manually position all those area lights on all those windows. If you had material portals, your workflow would be to go into edit mode, select all faces with the window material, dupe it, separate it into it's own object, then assign a portal material - MUCH MUCH MUCH FASTER.
    Easy answer - portal sampling is extremely slow. With just a handful of portals, it still doesn't matter too much compared to other parts of Cycles, but the slowdown is already noticeable.
    However, if "Portal" was a material, people would just throw it onto high-poly meshes (in this context, 20 faces is high-poly!). Consider your arched window example: Since it's a non-trivial shape because of the arch, you'd probably end up with hundreds of faces with the portal material, making rendering incredibly slow.
    Now, why does it work with "Every other soft on the planet" (which I doubt, by the way)? Probably, the answer is either that they use much simpler portal sampling logic or that they simplify your portal geometry internally (which could be done as a Blender add-on, by the way).
    Consider these two papers: https://www.solidangle.com/research/..._rectangle.pdf and http://noobody.org/PMEMS.pdf. Both are related to Portals (Cycles currently uses the first one, the second one is in code review right now), both use rectangular areas and their authors come from Solid Angle and Disney Research, so I'd guess using rectangles is not totally unreasonable
    Back to your cathedral example: The best approach is most likely to use two portals, one per side of the cathedral, that cover all the windows on these sides. Portals are allowed to cover occluded areas. It might lower the quality per sample slightly, but since it will be way faster (both the setup time and the rendering time per sample), it should pay off in the end.
    Last edited by lukasstockner97; 17-Aug-15 at 11:15. Reason: Typo



  11. #231
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    Originally Posted by Tea_Monster View Post
    Why are Blender's portals based on Area lamps? Every other soft on the planet has it as a material to be applied to a mesh. The work flow for portals in other soft is to select your window mesh, dupe it, and assign a portal material - job done.
    I believe there was a debate over this months ago, and the conclusion was that you can't make it any faster and more straightforward than having it be an option for the arealight. That is also not to mention that I think Sergey took issue with having it be a 'material' since for starters it wouldn't mesh in well with the node-based paradigm.

    Plus, Lukas is right, you have to realize the balance between wasted samples vs. overall sampling speed. Having a complicated polygon shape act as a portal would sharply curtail the wasted samples, but the speed penalty would be to the point where the net interior sampling rate per-minute ends up being far lower.
    Last edited by Ace Dragon; 17-Aug-15 at 13:06.
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  12. #232
    Originally Posted by Ace Dragon View Post
    That is also not to mention that I think Sergey took issue with having it be a 'material' since for starters it wouldn't mesh in well with the node-based paradigm.
    Sounds like a perfectly valid explanation on its own.



  13. #233
    Originally Posted by Tea_Monster View Post
    Every other soft on the planet has it as a material to be applied to a mesh.
    That's not true, both Vray and Mental Ray use area lights for portals. I'm only aware of Luxrender/Octane doing it this way, but iirc (I may be wrong on this) they don't have the more efficient analytic plane shapes for area lights either (i.e. area lights are really implemented as two triangles).



  14. #234
    Hello ! I'm wondering are area portals still useful in practice? I made some test with blender 2.77a and it doesn't look like so anymore. With area portals on I got worst results with a slight render penalty. Excluding that my simple setup is wrong what's going on?





  15. #235
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    Originally Posted by elaser View Post
    Hello ! I'm wondering are area portals still useful in practice? I made some test with blender 2.77a and it doesn't look like so anymore. With area portals on I got worst results with a slight render penalty. Excluding that my simple setup is wrong what's going on?
    They are useful in cases where the environment is the only light source.
    In your case I bet you haven't removed the area light in your no-portals test. So the area light is behaving as normal light source by throwing its light in the room.
    Try to remove the area light from the scene and you'll see the difference.

    If you ask why you can't use a mesh light or a area light instead of portals, well it's quite obvious.
    The light from portals have the same characteristics of the environment (color, intensity, bla bla bla....). But with the limitation that if you need other light sources, portals become useless.
    It depends on what you need.
    Last edited by LazyVirus; 08-Jun-16 at 12:32.
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  16. #236
    @LazyvVirus of course I know this, the test were made by turning on and off the "rendability" button of the area/portal "lamp" (or moving to another layer). The only source of light is the sky texture as you can see by yourself in the provided blend file.
    I've also tried with hdr and just plain white color, this is why I found it strange. Try yourself!



  17. #237
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    Originally Posted by elaser View Post
    @LazyvVirus of course I know this, the test were made by turning on and off the "rendability" button of the area/portal "lamp" (or moving to another layer). The only source of light is the sky texture as you can see by yourself in the provided blend file.
    I've also tried with hdr and just plain white color, this is why I found it strange. Try yourself!
    I tried deleting the portal light and got a noticeable difference. There might be a bug with renderability and portals.



  18. #238
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    Originally Posted by elaser;
    Try yourself!
    I did it, I had no issues. Without portal lamp the image has more noise.
    #NOTOBULLYING - Banned for self-irony - [Tutorial]How to moderate a community by Venerable Jason van de Burgos



  19. #239
    SORRY!!! I've just realized I didn't delete the default lamp when preparing the test scene. I can see now the effect it's clearly working.
    Sorry again for having wasted your time I feel so ashamed.



  20. #240
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    no worry, thanks for reviving the subject, tiny refreshment for thoughts and skill
    also, for reminding us to always check at least twice and not being afraid to ask if something feels off



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