On 22-8-2011 15:21, Mike the Elder wrote:

> Being a great Escher fan, I love it. One idea did occur to me that I'd like to
> share. Many of Escher's illusions worked all the better for the fact that the
> images were either monochromatic or rendered in a limited color palette. The
> bright blue background, although appealing for such a scenic image generally,
> may be wowrking against the illusion. The high-contrast diagonal between the
> land and sea cuts right across the bit where the "trick" occurs and tends to
> focus the viewer's attention just in the wrong spot.  As the various landscaping
> elements used in the land area are quite attractive, why not use them for the
> entire background and allow the illusion bit to blend in? Just a thought - great
> image either way.

That would be indeed a very Escher-like solution. And with a bit of fog 
or media in the background the construction would stand out like in many 
works of Escher.

Thomas

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Christian Froeschlin <chr### [at] chrfrde> wrote:
> Eriban wrote:
>
> > So I assume the attached image is more to your liking?
>
> Yes ;)

Okay, good to hear. :-)

> BTW the shadows are very hard and dark. If the tricks still
> work with area light and radiosity you could try these too.

I think I may be able to get area lights to work. I will give it a try.
Radiosity may be more difficult. Also, the computing power I have at my disposal
is a bit of a limiting factor. Rendering 600x800 with anti-aliasing already
takes more than four hours with the current image (on my six-year old Mac Mini).
And for printing the image on A4 format, which I intend to, I need to go to
2400x3600. The current trial render has been going for more than 14 hours now,
and isn't even halfway. That's without area lights and radiosity...

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Thomas de Groot <tenDOTlnDOTretniATtoorgedDOTt> wrote:
> Shouldn't the shadow of the construction touch also the grass, maybe the
> trees? It is tall enough for that it seems.

Yes, it should, really. I had already tried this, but did not get it to look
good. One problem is what the shadow should look like. It could be the top of a
single column (that's according to the shadows on the inner wall). However, what
then about the shadow of the square portal with two pillars? Showing a shadow on
the grass basically draws the attention to the fact that something odd is
happening here. Also, it simply did not look good (probably partly due to the
harsh shadows and lack of radiosity). So for now, I am taking the easy way out
here...

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"Mike the Elder" <nomail@nomail> wrote:
> Being a great Escher fan, I love it. One idea did occur to me that I'd like to
> share. Many of Escher's illusions worked all the better for the fact that the
> images were either monochromatic or rendered in a limited color palette. The
> bright blue background, although appealing for such a scenic image generally,
> may be wowrking against the illusion. The high-contrast diagonal between the
> land and sea cuts right across the bit where the "trick" occurs and tends to
> focus the viewer's attention just in the wrong spot.  As the various landscaping
> elements used in the land area are quite attractive, why not use them for the
> entire background and allow the illusion bit to blend in? Just a thought - great
> image either way.

Happy to hear that you like the image. Your suggestion is interesting, and I
like to give it a try. I'll post the result once I have done so (which may be a
while, as I am busy of the next couple of days). It's actually a bit similar to
the plan I first had. My initial idea was to let the grass slowly morph into an
abstract tiling pattern that would slowly fade out. That's also quite Escher
like. I discarded that without actually trying it out, however, because I
thought it would distract from the main illusion. Your suggest would probably
work better in that respect.

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On 22-8-2011 22:46, Eriban wrote:
> Thomas de Groot<tenDOTlnDOTretniATtoorgedDOTt>  wrote:
>> Shouldn't the shadow of the construction touch also the grass, maybe the
>> trees? It is tall enough for that it seems.
>
> Yes, it should, really. I had already tried this, but did not get it to look
> good. One problem is what the shadow should look like. It could be the top of a
> single column (that's according to the shadows on the inner wall). However, what
> then about the shadow of the square portal with two pillars? Showing a shadow on
> the grass basically draws the attention to the fact that something odd is
> happening here. Also, it simply did not look good (probably partly due to the
> harsh shadows and lack of radiosity). So for now, I am taking the easy way out
> here...
>
Fair enough. Imo, the shadow should look like the portal.

Thomas

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> Christian Froeschlin<chr### [at] chrfrde>  wrote:
>> Eriban wrote:
>>
>>> So I assume the attached image is more to your liking?
>>
>> Yes ;)
>
> Okay, good to hear. :-)
>
>> BTW the shadows are very hard and dark. If the tricks still
>> work with area light and radiosity you could try these too.
>
> I think I may be able to get area lights to work. I will give it a try.
> Radiosity may be more difficult. Also, the computing power I have at my disposal
> is a bit of a limiting factor. Rendering 600x800 with anti-aliasing already
> takes more than four hours with the current image (on my six-year old Mac Mini).
> And for printing the image on A4 format, which I intend to, I need to go to
> 2400x3600. The current trial render has been going for more than 14 hours now,
> and isn't even halfway. That's without area lights and radiosity...
>
>
>
If you try with an area light, don't forget to use adaptive.

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Attached is a new version, updated to take into account various comments. In
particular:
1) an area lights is used now,
2) the sea has been replaced by grass disappearing in a fog, and
3) the moment now casts a shadow on the grass (this works better now in
combination with the above two changes)

The lack of blue gives it an entirely different feel and I quite like the
result. Also nice is that the image is now quite different from other images I
have made, as many featured a lot of blue (water, skies, blue tiles, etc). So
thanks to all who have provided comments. Of course, feedback is still
appreciated on this image as well. :-)

Unfortunately, rendering time has exploded. It used to take less than two
minutes to render the scene without anti-aliasing at 600x800. That has now
become 25 minutes. This is even though area lights are adaptive, and the media
is very basic (fixed density and intervals set to 1). It is because the grass,
fog and area lights are each relatively expensive to render, and the combination
especially so. At the moment, the area lights have no added value inside the fog
(as there are no significant shadows there). However, I do not know yet of a
good way to exploit this to speed up rendering time. :-(

Cheers,
Erwin

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Attachments:
Download 'failure-variant4.jpg' (341 KB)

Preview of image 'failure-variant4.jpg'

> Attached is a new version, updated to take into account various comments. In
> particular:
> 1) an area lights is used now,
> 2) the sea has been replaced by grass disappearing in a fog, and
> 3) the moment now casts a shadow on the grass (this works better now in
> combination with the above two changes)
>
> The lack of blue gives it an entirely different feel and I quite like the
> result. Also nice is that the image is now quite different from other images I
> have made, as many featured a lot of blue (water, skies, blue tiles, etc). So
> thanks to all who have provided comments. Of course, feedback is still
> appreciated on this image as well. :-)
>
> Unfortunately, rendering time has exploded. It used to take less than two
> minutes to render the scene without anti-aliasing at 600x800. That has now
> become 25 minutes. This is even though area lights are adaptive, and the media
> is very basic (fixed density and intervals set to 1). It is because the grass,
> fog and area lights are each relatively expensive to render, and the combination
> especially so. At the moment, the area lights have no added value inside the fog
> (as there are no significant shadows there). However, I do not know yet of a
> good way to exploit this to speed up rendering time. :-(
>
> Cheers,
> Erwin

For your fog, are you using a media? Use a simple fog instead. fog is 
much faster than media, and in this case, should be a very good alternative.

Anyway, when using media, you should never use anything else than 
intervals 1, the effective default value.


Alain

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I really like this version!

One comment though (forgive me!). If you move the sun a tiny bit so that 
the shadow of the leftmost column falls behind the central column, the 
illusion will be even better I believe.

Well done!

Thomas

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Eriban wrote:

> At the moment, the area lights have no added value inside the fog
> (as there are no significant shadows there). However, I do not know yet of a
> good way to exploit this to speed up rendering time. :-(

As Alain mentioned, using media may be overkill for this kind of fog.
Apart from that, it might be possible to cut up the grass object into
one part that interacts with the rest of the scene (monument shadow)
and another part that doesn't, and use light_group's to restrict
the use of the area light to the part that needs it.

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