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Author Topic: Is this a known problem with ART?  (Read 9700 times)

ENSONIQ5

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Re: Is this a known problem with ART?
« Reply #15 on: September 04, 2009, 03:24:42 am »

From what I can tell the problem is that each material has a set range of illumination, from it's darkest possible value to it's lightest possible value.  In reality, all materials will be properly black in zero light conditions.  In the first image, the wall under the bed appears to merge into a uniform grey because that is as dark as that material can get.  The material used to define the slats under the bed, however, can get significantly darker.

About the only thing I can suggest here is to click the little padlock button between the Ambient and Diffuse colour settings for all materials, and set the Ambient colour to a much darker shade of the base colour, perhaps even black.  I suspect it won't really be possible to get a perfect image, because in reality the human eye/brain combination has the amazing ability to adjust itelf to all lighting conditions.  Fluorescent lights are actually greenish, for example, but we aren't usually aware of it because our brain decides it is the whitest thing in view, and is therefore white.
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Kyle

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Re: Is this a known problem with ART?
« Reply #16 on: September 04, 2009, 06:51:54 am »

green? I'd say their more yellow than green.  what are you going on that suggests its green? if our eyes pick it up as white/yellowish and cameras do the same, then for all intents and purposes they are. Im not even trying to match how our eyes view the world though, just standard cameras really. and even for a photo this would look off somehow.  I dont see how it would ever be black unless the lights were all spotlights high above the scene like a stage.  in a normal circumstance like this, there would be enough bounce light to illuminate the shadowy areas.
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ENSONIQ5

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Re: Is this a known problem with ART?
« Reply #17 on: September 04, 2009, 09:14:52 am »

It is surprising, but most fluoros used in offices and schools etc. are in fact greenish.  It has been demonstrated to me, using a white sheet of paper.  In a room lit by fluoros, curtains closed against the sun, a sheet of white paper appears white.  When a spot of sunlight is shone upon the sheet, transferred from the window sill via optical fibre, the paper turns suddenly green.  The brain takes the whitest thing and makes it white, and takes the blackest thing and makes it black.  Most digital cameras have a "fluorescent light" setting which offsets the green tint, if it isn't used pictures taken under fluoro lights can look rather ghastly.  In any scene your eyes detect, all shades and colours are adjusted so that the whitest colour appears white, the darkest colour appears black, and all other colours are stretched across the spectrum to suit. "Auto Adjust" features in Photoshop and similar packages use this concept to improve photographic images.  For more info regarding colour spectrum issues related to fluorescent lights see http://en.wikipedia.org/wiki/Fluorescent_lamp#Phosphors_and_the_spectrum_of_emitted_light

Anim8or does not take secondary illumination into account, ie. bounced light.  In effect, your only options are to "cheat", either by using extra lights, coloured to simulate secondary illumination, or by fiddling with AO and soft shadow settings.  The flat grey appearance of your shadowed walls is due to that colour/intensity being the darkest colour/intensity allowed for that material.  Resetting the material's Ambient colour to a darker shade should reduce the problem.  I have little knowledge of top-end packages like Lightwave, but from what I have seen secondary illumination is a phenomenon that is not very well accomodated by most renderers.

EDIT: I must also say thay your modelling is excellent, and these are among the nicest "Toy Story"-esque images I have seen rendered in Anim8or.  Nice work!

Another EDIT: Remember also that both human eyes and camera apertures adjust themselves depending on the brightness of the scene.  If some parts of the scene are quite bright, the lens or eye aperture will reduce, rendering the shadowy areas black, or close to it, even though they may in fact be moderately well illuminated.
« Last Edit: September 04, 2009, 09:35:47 am by ENSONIQ5 »
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Mills

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Re: Is this a known problem with ART?
« Reply #18 on: January 12, 2010, 11:10:29 am »

I realise this is an old topic, but it doesn't seem to have been fully answered.

Firstly, this is NOT a problem with the ART renderer.

As stated previously, the highlighted areas in the posted images are showing at their full ambient value (grey in most cases). This is because these areas are not receiving any diffuse light AT ALL, which leads to the conclusion that shadows from the included light sources have been set to 100%. Faces of objects not receiving ANY diffuse light can only display at their ambient value, so if a chair or a bed is causing total occlusion of an object (ie casting a 100% shadow), all faces in that shadow will only display their ambient colour, regardless of which 'way' they are facing in respect to any lights present.

Ambient light is represented as an artificial glow taken by objects in 3d applications. This is a crude, but usually effective, representation of what ambient light actually is, which is real light bouncing off a million different surfaces to the extent that it no longer has a 'direction'. You can see this effect yourself by rendering a scene with only one black light in it - you will still 'see' all of the objects in your scene, but they will be completely 'flat', and completely unaffected by where the black light is located. Diffuse (scene) lighting is what gives them 'volume'. If you want to use 100% shadows, you really need to be setting all of your ambient colours to 0, and placing your own ambient light sources in your scenes.

The easiest way to 'fix' this would be to reduce your shadow level from all lights, generally a value of about 95% or just above looks best in this sort of scene.

Your alternative (as stated) is to have an additional, low level light source in the centre of the room. Not adding any shadows to this light will provide the 'volume' you are looking for, even on the surfaces which are not apparently facing the light (eg under the bed, or the side of the night-stand).

Also as stated, excellent work on the models Kyle, your renders look superb, I hope you get them looking exactly how you want!
« Last Edit: January 12, 2010, 11:12:55 am by Mills »
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Kyle

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Re: Is this a known problem with ART?
« Reply #19 on: January 15, 2010, 06:35:39 am »

Well, your post makes the most sense to me so far, I'll give it a shot some time.

If only I could get Animi8or to run on my new laptop...

Edit: Actuially according to steve that suggestion wouldnt work either. not with ART anyway. This is a copy/paste from an old post of steve's

The missing feature from ART is the ability for each object to cast shadows or not.  They all cast shadows at 100% dark.  The scanline renderer allows them not to and to only cast a partial shadow.

So when it comes to the ray tracer, it seems the problem I mentioned is in fact a problem with ART because it doesn't allow partial shadows. right?
« Last Edit: January 15, 2010, 11:13:02 pm by Kyle »
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Mills

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Re: Is this a known problem with ART?
« Reply #20 on: January 16, 2010, 01:47:22 am »

Sounds absolutely right to me, Kyle. I must confess I hadn't used ART to that degree as I still tend to stick with v.95. Always happy to be corrected! I do remain fairly sure this is the cause of flatness in your images, but I guess it's more a 'known limitation' than a 'bug' as such?
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hihosilver

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Re: Is this a known problem with ART?
« Reply #21 on: January 16, 2010, 08:27:06 am »

Well, it seems to me that, although it may cast shadows at 100% dark, the 100% dark with a higher ambient value would still not be a pure black shadow.
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Mills

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Re: Is this a known problem with ART?
« Reply #22 on: January 16, 2010, 07:39:11 pm »

But it still produces a 'flat' look to the image, hiho, as the ambient component doesn't react to the positioning of lights within a scene. So every face, whether facing a light or not, will show just the ambient colour, producing the grey areas seen in these images.
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hihosilver

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Re: Is this a known problem with ART?
« Reply #23 on: January 16, 2010, 07:45:40 pm »

That's exactly what I'm saying
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