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Author Topic: Global illumination here we come!  (Read 9228 times)
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twinbee
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« Reply #15 on: March 17, 2010, 03:16:24 PM »

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Cool ! On the last picture it really starts to be difficult to distinguish it from a real ceramics molded object !

Is that the one in my first post, or the 'snow' one?

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Nice! Will your renderer be available for us to try out?

I'd still like to release software with a full GUI at some point. But before then, everything needs unifying more, and I'd like to port it to the GPU for speed...

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I was wondering, is there some point at which it would be easier to export fractal shots as high res meshes and import them into a rendering package?
Then you could use all sorts of techniques, like depth of field, reflections, refraction, high dynamic range, multiple light sources etc.

Or would it maybe be too hard to decide which parts of the fractal to export?

Yeah, the whole thing is so tricky, not least because of the resolution. Programs which convert voxels to polygons seem few and far between, and can only seem to handle a limited number of polygons. In principle though, it shouldn't be too hard program really (marching cubes algorithm), and understanding a polygon format to convert to. I'm still a little surprised there's no real standard 'voxel format' in place.

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The global ones appear as if the lens on a camera is way out of focus (or I have forgotten to put on my glasses).

The blurring present wasn't by choice. As I said in my previous post, it is a bug in the algorithm. I think I know what's causing the problem, and in fact I even managed to 'fix' it, but something else broke, so I need to investigate further. It's also what's causing the dark outlines that are appearing.

Apart from that, one can always increase the resolution, and then resize to make smaller, but obviously I would like to solve the problem.

Anyway, hopefully I can change your opinion about GI once I fix the bug wink

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Why do some fanatics prefer blurry out of focus digital images, instead of something with visible details??

I think given the choice, anyone would prefer decent anti-aliasing/downsampling over a blurred image. However, pictures with a shallow depth of field, like Lycium's amazing 'Rise' certainly seem to benefit from the added 'blur' without losing anything:
http://lyc.deviantart.com/art/rise-64751071

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simulating reality isn't for everyone, there will always be a place for abstract CG

Going to the cinema the other night, the entrance to the seating area was a a long dark corridor (felt material?) with lovely mini lights dotted all along. It was quite surreal, and quite CGI-ish. I think given the right materials (some may be impossible to create) and lighting, real life can be incredibly CGI-like smiley

I'm beginning to think anyway that the 'DI look' can be achieved with GI simply by using smaller lights rather than an entire sky light. Perhaps something closer to the red picture for instance.

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nice one twinbee smiley since i work on indigo now, i should probably try adding support for intersecting the mandelbulb sometime! (though i don't have a lot of free time for fractals these days, as you guys have probably noticed)

Lack of time... sigh, yes, I know how that feels, though I'd still like to see more renders from you these days! tongue stuck out I bet you'd do some great stuff with the Mandelbox too.

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Your images have "holes" everywhere, mine have just flat surfaces. If I increase the number of iterations in order to get "holes", a few appear, but then I need to apply a heavy anti aliasing in order to remove coarseness.

One idea to reduce the 'flatness' which I have sometimes used in the past is to have the z ray travel twice as slow (or less) as it should, relative to the x and y light rays. It's an artificial fix, but it may help...

Sockratease, that HDRI technique sounds interesting - I wonder what lighting effects can't be simulated with that...

Here's another render from last night. I think it has a 'pearl'-like sub-surface scatter look, but heh, I didn't really intend that. Just changing one or two numbers in the algorithm can produce very different results.

« Last Edit: March 17, 2010, 03:26:40 PM by twinbee » Logged
kram1032
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« Reply #16 on: March 17, 2010, 06:44:15 PM »

Great latest image cheesy
Already got back a lot of its sharpness smiley

The problem now is the inverting colours in too bright spots, right? (I see some cyan specular highlights which surely are supposed to be white or orangeish...)

@Lycium:
Natively supporting fractals (or algoritmic geometries) would be an excellent test for Indigos algorithms, right?
You said yourself already, fully raytracing a fractal isn't exactly an easy thing to do, as a lot of rays are gone for good in the extremely fine (infinite) details...

Did you see the thread on "colouring fractals in their true colour"?
(Something like that at least)
Do you think, you could do that? - Using the details of a fractal and interpretting them as thin soap-bubble-like walls which cause reflection and refraction in different colours due to different path-lenghts?
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Tglad
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« Reply #17 on: March 18, 2010, 12:24:41 AM »

Sockratease, I don't understand how HDRI is in any way connected to GI. As I know it high dynamic range just means you store pixels with much bigger range than 0 to 255. This allows you to record really bright things in the image which helps with adding glare or changing the exposure of the image, e.g. when you look at the sun you can darken the rest of the image and the sun remains bright.
Twinbee, yes you would think someone would have made a standard oct-tree voxel format that rendering packages could use, or perhaps even some sort of 3d jpeg. But it wouldn't be easy to select the voxels if you're in a deep zoom, you might be looking off into the far distance, or the voxels on screen may be close but a shadow is coming from a far distance. And the data size could be very large.
myrtlesoftware.com is the only voxel renderer I found after a quick google, but it deals with transparent voxels mainly, and talks about 4k data sets, ha!
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cKleinhuis
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« Reply #18 on: March 18, 2010, 12:35:29 AM »

@tglad hdr is for getting more detail out of large ranges, especially high and low e.g. the sun and a shadowed place
i ised the formula n/(n+1) as a map for my values, getting a more  smooth behaviour in areas with great values fiery
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Sockratease
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« Reply #19 on: March 18, 2010, 01:20:40 AM »

Sockratease, I don't understand how HDRI is in any way connected to GI. As I know it high dynamic range just means you store pixels with much bigger range than 0 to 255. This allows you to record really bright things in the image which helps with adding glare or changing the exposure of the image, e.g. when you look at the sun you can darken the rest of the image and the sun remains bright.

Such images (hdr) can be used by software as a light source. They superimpose the image on a virtual sphere surrounding the scene, and it sort of "projects" everywhere.

They give results at least as good as GI and do not suffer the render time impact that is associated with Global Illumination.

It's not related to GI - it's a substitute for it.

I can find articles on it that can explain it better than I can if you want to know how it works.  It's a mainstay in most 3D Software I know.

From what I heard about it at a 3D forum;

The general  idea is mainly intended to be used along side normal lights. They're there to provide over all hue and subtle lighting, filling in spots regular lighting often can't... And it does it in a way "Ambient Lighting" can't live up to.

HDRIs are actually meant to be used for capturing a scene's lighting for putting CG inside of live action pictures or video. A lot of times you'll see in "making of" videos for movies which use a lot of CG+live action that they have a diffuse ball painted a certain value of gray in the scene. This is for calibrating an HDRI they made of that scene to the same value of gray used on a sphere in their 3D program. Then whatever 3D content they render out will have the same (or close to) lighting of the live action place they filmed.

People eventually branched off from the diffuse balls and started using HDRIs just as a simple, easy way to get high quality lighting. You don't have to fumble around with numerous light sources. You just load an HDRI image, maybe add one spot light for shadows and render.

Results comparable to GI with very little hit on the render time.

Sounds like it may help here.  After all - be it a Mandelbulb, Maya, or Bryce - It's all 3D Rendering using mostly the same basic principles for making the final picture.


« Last Edit: March 18, 2010, 01:33:44 AM by Sockratease, Reason: Speelinf Eroorz » Logged

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lycium
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« Reply #20 on: March 18, 2010, 05:55:33 AM »

They give results at least as good as GI and do not suffer the render time impact that is associated with Global Illumination.

It's not related to GI - it's a substitute for it.
HDRI isn't really a substitute for GI, it's another source of illumination (for environment lighting) as you mentioned, unrelated to the rendering algorithm in use. For example Twinbee's earlier renderings used a non-constant sky colour, probably with high dynamic range - he's still using that now it seems, but he's also considering secondary light bounces. My images on his page (also in the first article) rendered with GI as well.
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Sockratease
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« Reply #21 on: March 18, 2010, 12:05:41 PM »

They give results at least as good as GI and do not suffer the render time impact that is associated with Global Illumination.

It's not related to GI - it's a substitute for it.
HDRI isn't really a substitute for GI, it's another source of illumination (for environment lighting) as you mentioned, unrelated to the rendering algorithm in use. For example Twinbee's earlier renderings used a non-constant sky colour, probably with high dynamic range - he's still using that now it seems, but he's also considering secondary light bounces. My images on his page (also in the first article) rendered with GI as well.

Well...  I use it as a substitute for GI all the time in 3D work.  So I have no issues calling it such.

Plus, it has the added advantage of supplying reflective surfaces something to reflect - a nice trick if put to abstract use   afro
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visual.bermarte
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« Reply #22 on: March 18, 2010, 12:42:21 PM »

Hi!
regarding meshes..
I did a few tests using mandelbulb and mandelbox's slices (1 pixel) producing 3d objects using imageJ plus mandelbulb3D (thanx to Jesse).
The result is not so impressive according to me but it's ok for a test.
The very first time I used images produced by Daniel White (thank you!).
I think it's better to produce a 3d mesh of the bulb zooming a little bit inside a corner.. I will try it.
The meshes are usually 10-12 MB; so if I put together 4 meshes to obtain a better bulb would be 4 times bigger!
Morphing from power to power would be a problem; how many objects are necessary to morph a bulb from pow2 to pow3?? (this thing I could try as well).
the first one (Daniel's) has Sub Surface Scattering on, the other two are created using Jesse's mandelbulb3D.


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twinbee
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« Reply #23 on: April 02, 2010, 05:17:37 PM »

Here's the GI version that I should have posted first time. It regains the crispness, and the old clay/plaster look that was present in the old renders (the glossy look was actually a bug, but it's easy to add even now if need be).



Hopefully, this one is more to Paul's tastes! ;-) I still have a feeling though that it's not quite how real global illumination with a perfectly diffuse, plain white surface, and a full-cover skylight, would appear. The reason being is I still haven't implemented 'underside' surface reflection, so overall brightness/contrast is almost a guessing game. I have a feeling that real GI would instead look as if covered in white paint, perhaps a bit more like this next picture (but less snowy, and without the 'black bits'):

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Nahee_Enterprises
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« Reply #24 on: April 08, 2010, 10:11:24 PM »

Here's the GI version that I should have posted first time.  It regains the crispness,
and the old clay/plaster look that was present in the old renders....

Hopefully, this one is more to Paul's tastes!  ;-)   I still have a feeling though that
it's not quite how real global illumination with a perfectly diffuse, plain white surface,
and a full-cover skylight, would appear.

It definitely is better than the first GI version you posted.    cheesy   But I would not go so far as to state "(no blurring)".  Maybe very little blurring is a bit more accurate.  (My tastes are bit more discriminating.)    wink

If you look at the same area I pointed out before (below):
  
You can see in your latest GI version posted, that there are still areas which are unclear in detail.  The DI version is quite sharp in showing what is actually there, even down to the smallest pixel level.  To me that is what I call "normal", because I have very good near-vision, and expect images to contain the same level of detail.

I guess it does come down to personal tastes (which is how I will rate and vote on images and videos).
 
« Last Edit: April 08, 2010, 10:14:09 PM by Nahee_Enterprises » Logged

twinbee
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« Reply #25 on: April 09, 2010, 02:05:01 AM »

Thanks for giving your honest opinion.

But hang on, I think FF resized the image in your browser. You need to copy to the clipboard (or save the picture directly), and then paste/load into a picture viewer. If you just 'grab' the screen, you're getting the more blurred version (at least that's the only thing I can think of).

You should have gotten this:


* compare.png (66.14 KB, 212x189 - viewed 1119 times.)
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Nahee_Enterprises
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« Reply #26 on: April 11, 2010, 11:02:47 PM »

Thanks for giving your honest opinion.

You are most welcome.  And I always give such.  The problem is that most people can not handle that much honesty.  Most people state that if one cannot say something nice and positive, then they should not say anything at all.  I would rather give (and receive) the blunt facts and truth.

But hang on, I think FF resized the image in your browser.

As I already stated:  "It definitely is better than the first GI version you posted."  But:  "....there are still areas which are unclear in detail."

And this has me wondering.  I have already stated I have Near-Vision, I can see things extremely well when they are close.  But I need corrective lenses to see things far away, otherwise everything looks like your first GI image.  Are you Near or Far Sighted ??
 
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twinbee
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« Reply #27 on: April 12, 2010, 08:25:12 PM »

I think what I was trying to say was that with big pictures, Fractalforums.com resizes the picture to make it smaller (and therefore, makes it seem a bit more blurred than it really is). I'll post my latest comparison again, but this time zoomed in. Although parts are less contrasted in the GI version (as a natural consequence of global illumination), there's not even any anti-aliasing, let alone blurring on the GI version. See the parts circled by green circles - the pixels are fully there and precise. The jpeg artifacts cause the GI version to be more blurred in the red circle than it should be - I'll post the original PNGs if I can find the DI PNG version. So what do you think of this below:



I'm near-sighted anyway for the record, but apart from jpeg artifacts like the section in the red circle, it seems clear even upon zooming in, that there's not any more blurring than with direct illumination. Only less contrast (which I guess may look as though it's more blurred in a way), so I see what you mean up to a point.

** EDITED TO ADD CIRCLES **
« Last Edit: April 12, 2010, 08:49:52 PM by twinbee » Logged
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« Reply #28 on: April 12, 2010, 11:26:16 PM »

....Fractalforums.com resizes the picture to make it smaller.....
Although parts are less contrasted in the GI version....
The JPEG artifacts cause the GI version to be more blurred....
Only less contrast (which I guess may look as though it's more blurred in a way),
so I see what you mean up to a point.

Then I guess, in this case, it must be both the contrast and the JPEG compression that causes what I call areas of blurring.  It would be interesting to see the original .PNG outputs for the DI and GI versions.

I still feel that some of what the GI is doing tends to soften "edges" too much and make them appear as if they are rounded instead of maybe sharp.  See the area just to the left of the red circle??  It looks like a depression in the surface.  In the DI version, it almost appears to have a "lip" on the far left side of that sunken area.  But the GI version is more like a soft rounding over into the depression, no "lip".

Oh well, just a matter of taste as to what looks best to different people.    wink
 
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twinbee
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« Reply #29 on: April 12, 2010, 11:50:45 PM »

I'll keep looking for the other DI PNG.

I agree with you about how the 'lip' part looks sort of better in the DI version.

There are a few things to say however. One is that this I might need to render at higher resolution to obtain the same effect in GI. And two, that that 'lip' effect shouldn't be there, and that's an artifact that DI produces, but which shouldn't. In other words, GI can create that too, but then the apparent lip would have to be actually there in the first place.

In any case, a proper implementation of GI with underside surfaces/reflections might also fix it. My current implementation is only a kludge so far really. And the final thing and most probable thing is, that lip might also be far more noticable if I used a single smaller directional light source, (instead of a full skylight which tends to produce less contrast, and reduce shadows generally). In other words, you would tend to prefer smaller light sources rather than DI over GI per se.

I might as well post the PNG of the GI version. It may not be a fair comparison admittedly though, until I find the DI PNG too:


* gi2.png (66.59 KB, 211x186 - viewed 1018 times.)
« Last Edit: April 12, 2010, 11:54:45 PM by twinbee » Logged
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