Scene to learn appleseed


#1

HI Everyone, long time ago I discovered Appleseed renderer but I confess never started really using for many reasons, I always kept an eye on the project, and the will to learn has always been there growing, I now decided to learn all about it.
I created a quick scene to test few things, a simple “LIght Bulb Scene” I would like to render two versions:

  1. the easy one, light bulb off, it is lit by external light light a photo studio setup.
  2. the harder one all dark, only the fiament incandescence glowing illuminating the scene.

I have the geometry ready and I would appreciate any hints or tips you would offer to guide me in the rigt diretion to accomplish the results I look for.


#2

Hi, welcome!

Great question. For the second case to work efficiently with path tracing, you’ll need to make a small sacrifice to the God of Physical Correctness and make the glass bulb invisible to shadow rays. I don’t recall how this is done in blenderseed but @Jonathan_Dent certainly knows.


#3

For the first step I got at this stage…

it is not clear what is the preferable way to lit a scene (Mesh ight, point light, spot light, ibl) I would love to contribute to the project producing a visual comparison of the different lights (correlated with data values and theory) if not already available.
scene set up:


#4

All these are valid and efficient ways to lit a scene, it really depends on what you want to achieve.

We don’t have that at the moment, and it would be a very welcome contribution!

Regarding the light bulb, it really needs to be invisible to shadow rays. You should be able to uncheck shadow ray visibility on the light bulb object itself.


#5

Object visibility flags can be set in the git-version of blenderseed.
(Screenshot on the righthand side shows “Appleseed Object Flags”)


#6

So before the git become “official binary release” there is no way to make that scene?
any guide on how to install the git version?


#7

Hi Zaldor, the blenderseed plugin doesn’t need to be compiled unlike the Max & Maya versions. You can just download the git-version and drop it into Blender addons. True, I use it together with a self compiled version of of the latest appleseed sources. If blenderseed-git works flawlessly with the older official 1.8.1 binaries I have not tried but you may give it a go.


#8

Noisy Update:

Once solved the problem of the blenderseed version that allows to flag an object visibility to shadows, I went straight to the filament as “only light scenario”, I checked the “LIGHT” checkbox on the Filament material but was unsure how to control brightness, I bumped up “Exposure” as it seamed the relevant one, but having no clue of what scale it was refering to, I had to guess, first 1 than 2,3,4, than 40 (too much!) 20, and settled for 15. I would have appreciated having a more familiar way to judge the input value and predict the outcome, like watts, lumen etc…
for the glass, I selected “Glass BSDF”, not sure if it was the best option, all parameter are as default apart from roughness which was set to 0, also here, most paramenters felt quite cryptic.
All the other materials are diffeent configuration of the Disney BRDF which is much more familiar (Coming from Cycles) but I couldn’t find transmittance in the shader.

Now I have to figure out how to lower the noise…


#9

I think the noise might be due to surfaces close to the filament, and thus being brightly illuminated. In the context of global illumination, these surfaces themselves become light emitters but they cannot be efficiently sampled, hence fireflies.

There are many ways to keep these fireflies under control, one of them is to set the Max Ray Intensity parameter (a global rendering parameter) to some value. Start with 1 and try to increase it progressively.


#10

Current path tracing integrator struggles a lot compared to other render engines, the alternative would to use SPPM.

Regarding light intensity is kind of weird to tweak it for me too, when I read the word ‘exposure’ is always a camera related setting. Still today for me is kind of hard to grasp light terminology. What can be done is to adopt luminous intensity in IS units.

Transmittance or what we call in appleseed ‘refraction’ is not yet included in Disney BRDF, you could use asStandardSurface.

One way to reduce fireflies is to activate Max Ray intensity:

image


#11

Hi Zaldor,
what you ask of the render engine is really difficult: a small, intense light source inside a reflective-transmissive surface for scene lighting. For this bidirectional path tracing with Metropolis light transport would be indicated.
I added a zipped Blender file with the scene shown in the image. It’s an adaption of an old YafaRay example scene by Kronos redone for appleseed.

bulbs1_as.zip (144.9 KB)


#12

@Mango3 Nice!

Now that I think of it, another source of noise and fireflies will be rays randomly hitting the filament. To fix that, the filament must be made invisible to diffuse and possibly glossy rays.


#13

Ok Wrong scene to start with! :smiley:
I come up with another one less difficult for the engine.


#14

@Zaldor Keep em coming! These scenes are great. They may raise the blood-pressure of @franz and the other talented devs but they are exactly the type which showcase the limits of the underlying algorithms used and their implementation. Now the devs are surely keenly aware of what scenes are “difficult” for appleseed given that bidirectional rendering in appleseed is already on the horizon. For the stated target market vfx these type of scenes are not really a pressing issue though personally I’m really thankful for the devs hard work to have spectral, SPPM, good caustics and soon bidirectional rendering available.


#15

All unidirectional path tracers will struggle in this scene unless measures are taken. It’s a fundamental limitation of unidirectional path tracers.

SPPM would be an alternative but (1) it’s still relatively experimental in appleseed even if it works well in practice, (2) it’s not exposed in blenderseed and (3) it comes with its own set of limitations, biased in the form of blurriness being one of them.


#16

I don’t think it’s a particularly challenging scene. Visibility of the objects with respect to certain ray types must be adjusted. You’ll have the exact same problem with Cycles, Arnold, etc.


#17

Actually SPPM is in blenderseed. I’ve never tried it out though.


#18

Yeah I just saw that, pretty cool!