Author Topic: Strata  (Read 28127 times)

Offline efflux

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Re: Strata
« Reply #15 on: August 04, 2009, 05:21:00 AM »
By the way, Mojoworld spends ages doing a whole bunch of calculations before it even starts rendering. I'm guessing it's doing these various optimizations during that time. The fact that the displacements disappear in the distance is one of my pet hates with Mojo. it ruins anything with any serious overhangs and makes distant objects look typically  CG smooth.

Offline efflux

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Re: Strata
« Reply #16 on: August 04, 2009, 06:44:45 AM »
This is not a great example and very small but it's enough to show the effect. I might get a better render later and do further tests.

Render setting are:

Detail - 0.8
Antii-aliasing - 3
No GI because this doesn't make any difference to the problem.
Shadows are obviously on since this is when you see the problem.

The picture that has less of the small black dots has Microvertex jittering and detail jittering turned on but I think microvertex jittering is the setting that improves it. I can't confirm that this is always successful. Increasing detail improves things as well. Detail 1 can still exhibit the problem just not too noticeable.

Offline efflux

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Re: Strata
« Reply #17 on: August 04, 2009, 06:49:47 AM »
Also, in this particular corner of this rock I did at one time see an odd twisted form under the surface appearing during render. This only happened once at some particular POV and render setting. This terrain is two fractals blended and this line is at the blend but it makes no difference really. Any place where there are any twists or stretches of geometry at sharper angles can exhibit this problem.

Offline efflux

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Re: Strata
« Reply #18 on: August 04, 2009, 07:01:15 AM »
I'll set up a better example of this at some stage by having much smoother shapes but stretched then displaced.

Offline efflux

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Re: Strata
« Reply #19 on: August 04, 2009, 07:07:15 AM »
Is is just a case that at certain small angles and directions the triangular polygons have a problem creating a nice crease?

Offline inkydigit

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Re: Strata
« Reply #20 on: August 04, 2009, 07:31:05 AM »
these are fascinating and awesome...thanks for sharing your insight!

Offline Matt

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Re: Strata
« Reply #21 on: August 04, 2009, 12:31:24 PM »
By the way, Mojoworld spends ages doing a whole bunch of calculations before it even starts rendering. I'm guessing it's doing these various optimizations during that time. The fact that the displacements disappear in the distance is one of my pet hates with Mojo. it ruins anything with any serious overhangs and makes distant objects look typically  CG smooth.

Yep. Whether you do the calculations up front, or during the render, they have to be done at some point :)  And I made a decision to keep horizon details reasonably high in TG, even knowing that things could be faster if I took the kinds of shortcuts it sounds like Mojo takes. I do reduce detail near the horizon, just not enough that you can really see it happening.

Matt
Just because milk is white doesn't mean that clouds are made of milk.

Offline Matt

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Re: Strata
« Reply #22 on: August 04, 2009, 12:39:04 PM »
The only solution to reduce the crinkliness of sharp geometric edges is higher detail settings. It's basically a sampling problem.

Regarding the blotchy shadows, yes they could be fixed by using the same detail in my shadow casting geometry as the visible geometry, but you wouldn't like the render times. Again, increasing detail should reduce their visibility.

Because increasing detail solves various problems, it's better to increase detail and leave some of the other expensive aspects of the renderer at relatively lower details to keep render times reasonable. That way you can increase detail to solve various problems at the same time.

If I make a setting that allows you to adjust relative detail of the shadow casting geometry, everybody will crank it up to 1 for their final renders when they don't need to, making their renders much slower. Sometimes it's better not to give the user too much power. I hope you understand where I'm coming from ;)

Matt
« Last Edit: August 04, 2009, 12:41:24 PM by Matt »
Just because milk is white doesn't mean that clouds are made of milk.

Offline Cyber-Angel

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Re: Strata
« Reply #23 on: August 04, 2009, 02:09:44 PM »
The question of detail is a matter of perception more over it is an artifact of the Human visual system, in real life the amount of detail that can be perceived is dependent on the objective distance in relation too the viewer; that is to say that too the eye there will be more detail on a tree a distance of three feet than one at fifty or a hundred feet away given ideal viewing conditions.

There are many mitigating factors that govern detail and the amount of same that can be observed these include and are not limited too, Age of viewing subject (Visual Acuity decreases with age), Visual Anomalies in the eyesight of viewing subject such as impaired depth perception weather acquired such age, by birth or by other means, neurological particularly degeneration or injury too the Visual Cortex, other factors include line of sight and particularity obstructions  between the viewer and the object been viewed, attitude difference between object and the viewer, meteorological phenomena such as fog, time of day and sun angle relative to the observers viewing angle among others.

There is a mechanism in the brain (I do not know its name, for the record) that protects us form sensory overload it acts as a filter preventing us from neurological distress the eye picks up a tremendous amount of detail, that we are not aware of, when absent the detail is missed: this then is the fundamental failing of CGI and why research in the area is ongoing too give our Augmented Reality via various means what nature and the ravages of time give us for free.

It is our artistic wish to capture a moment in time and freeze it for others who'd come after we have all long turned too dust and that dust has been scattered by the winds of ages may get a scene just for a moment of that moment in time. Our ancestors did it with the first cave painting over time the methods changed but the passion to create never has, need we defile their grace that long line of artists who have gone before or do we instead honor them and be thankful for what we have, despite its failings?

All good things come in time, the faults of TG2 are included in this.

Regards to you.

Cyber-Angel ;D                                             

Offline littlecannon

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Re: Strata
« Reply #24 on: August 04, 2009, 04:23:48 PM »
On a side note, you can induce hypnotic trance by overloading the conscious mind, another good reason to have the "Reality FilterŪ" in place.
cheers, Simon. (going off on a tangent).
I just need to tweak that texture a bit more...

Offline efflux

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Re: Strata
« Reply #25 on: August 04, 2009, 04:41:34 PM »
Regarding the blotchy shadows, yes they could be fixed by using the same detail in my shadow casting geometry as the visible geometry, but you wouldn't like the render times. Again, increasing detail should reduce their visibility.



This is exactly what I thought the problem was because you can increase detail and any nasty geometry does smooth out but it seemed like the shadows were being calculated at levels where the geometry showed the problems.

I think at present it is possible to crank the detail up enough to be not too slow and get rid of any problems at least enough so that they can be taken out with some simple post work. I went back to some scenes where this problem was bad but since I did them the rendering speeds of TG2 have improved making it possible to bump up the detail a lot more. Microvertex jittering does seem to help. Not sure why.

Offline efflux

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Re: Strata
« Reply #26 on: August 04, 2009, 04:55:52 PM »
Just a note on those files I posted.

I'm not going further with this technique. As far as I'm concerned it's sorted. Perlin Strata 2 is the best one for getting more detail and interest in the strata if that's what you want but Perlin Strata 4 is the best for simple strata. The strata might often just be some colour where other components in the scene provide detail. So this file should be the most useful. Perlin Strata 3, as you will see, distorts the strata totally away from being horizontal in places. This can also provide an interesting effect.

Also, if you look at Perlin Strata 2 you will find that the scale of the smallest and largest feature sizes of the strata is controlled in the fractal's colour tab. The scale tab controls the overall size of the distortion. If you tweak with these settings you can go to any extreme desired - subtle undulations or huge twisting shapes. Perlin Strata 4 does a similar thing but without using a fractal.
« Last Edit: August 04, 2009, 05:09:16 PM by efflux »

Offline littlecannon

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Re: Strata
« Reply #27 on: August 04, 2009, 04:58:47 PM »
Thanks very much for the files and experiments in strata efflux, interesting stuff.
I just need to tweak that texture a bit more...

Offline efflux

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Re: Strata
« Reply #28 on: August 04, 2009, 05:21:50 PM »
By the way, I have found an awesome way to get multicoloured strata from an image file. The beauty is in the way Gimp (open source image editor) can create an incredibly complex gradient from a colour palette. It's really quick and easy to do. I will post eventually about that. Photoshop may have the same capability.

Offline efflux

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Re: Strata
« Reply #29 on: August 04, 2009, 05:25:11 PM »
There is also a way to get multicoloured strata using a colour gradient hack I made. I'm sure I posted one of these in the forum but I will revisit that idea. The hack is very complicated and a bit slow.

This is one reason for a TG2 colour gradient  :)

 

anything