Features

Download

Online

Gallery

Blog

  Index  | Recent Threads  | List Attachments  | Help  | Search
 Welcome Guest  |  Register  |  Login
Login Name  Password
 

Sweet Home 3D Forum



No member browsing this thread
Thread Status: Active
Total posts in this thread: 31
Posts: 31   Pages: 4   [ Previous Page | 1 2 3 4 | Next Page ]
[ Jump to Last Post ]
Post new Thread
Author
Previous Thread This topic has been viewed 19529 times and has 30 replies Next Thread
okh
Advanced Member




Joined: May 12, 2013
Post Count: 1286
Status: Offline
Reply to this Post  Reply with Quote 
Re: This is cheating...

Thanks for testing this, Cec. Good to know, your conclusion pretty much sums it up and I love the way you always provide brilliant illustrations. Also, there are the tricks in VeroniQ's blog post about adding scenery.

I admit to a fondness for the 360° panorama textured sky. This works quite well if you - for whatever reason - want as little clutter in your plan as possible, have a distant view from the construction and want to limit the file size. The images below is from a sh3d file that compressed is < 192KB - where the sky texture and the curved tree line account for some 50% - the panorama background is a 1600×600 <40KB jpg stitched together with the Gimp. Sure, the result is pretty basic, but it will help visualize the view around the building and a will provide a lot of effect with little added file-size.

If the background has mountains or other objects that go far above the horizon, there are some distortion issues which may have to do with the equirectangular projection (?). And the 3D view and the photo-rendering seem to give slightly different perspectives (see feature request 668).

ok


[Oct 25, 2016 9:36:44 AM] Show Printable Version of Post    View Member Profile    Send Private Message    Hidden to Guest [Link] Report threatening or abusive post: please login first  Go to top 
Ceciliabr
Advanced Member
Member's Avatar

Denmark
Joined: Jul 7, 2013
Post Count: 205
Status: Offline
Reply to this Post  Reply with Quote 
Re: This is cheating...

@okh
I admit to a fondness for the 360° panorama textured sky. This works quite well if you - for whatever reason - want as little clutter in your plan as possible, have a distant view from the construction and want to limit the file size.


Yes, the 360 panorama sky/horizon works well. I can admit that.

The cluttering is avoided if you use Levels and Shift+Command+H for hide and view.

A distant view will in fact become more realistic with a 3D horizon, because the size of the sky projection is locked to the field of view.

And yes, the size is increased – but not a lot though, since a high resolution panorama image can weigh just as much as a 3D-modeled horizon.

And then, of course,if you are seeking realism, you are stuck with the direction of the shadows, and have to find the right position of the sun.

And lastly, the real world offers a lot of details. It's dirty, eroded and organic.
3D-models with limited file-size are mostly clean to the point of being sterile, since tiny textures tends to become tiles if they have any irregularities in them.
The models will not blend in properly, like you can see when looking more closely at the 5th image in my last post. Even if I did my best to colour-correct the highlights and match the shadows, it's still obvious that the picture is a combination of two different images.

Well... I'm just looking for arguments...



However, I have looked at the blog post you recommended, and feel I need to comment on the methods that are suggested.



Using a non-square image will not give the best result, as the sky is actually projected from a square image.

A rectangular image is automatically stretched to fit a square when it is applied to the sky, and it will appear oversized and loose a portion of it's original resolution. A 4096X1024 image will lose 3/4 of its resolution.
Applying a rectangular 4096x1024 image will look like this:



Fitting the image to a square matrix is a better way to apply an image to the sky. Then it will keep most of it's qualities:


And it will render like this:


But then there's the distortion that we have to adjust for:



Now it renders like this:


The sky image used in the above renderings is the one used as example in the blog-post, and not a high quality image.
Here I have changed to a better quality image:


So it's absolutely possible to get a great looking sky.
But I' don't think the same goes for the horizon.

In my opinion, the drawback with having the horizon fixed to the sky, is that it will not change perspective or size
unless you change the Field of view on the camera.
Moving the camera further back, will only change the size of the 3D objects, and there's no way to avoid a mismatch unless you zoom in or out.




When using a 3D horizon, that's not an issue.
Here is a close camera position:



And moving the camera back, here is a far cameraposition, with the same field of view:



The size of the horizon and the trees will follow the camera movement.

I have constructed a Matrix that is quite handy for users who want to make a distortion-free sky without to much trial and error. It's a 4096x4096 jpg-file, 454 kb. It's also handy for making UV-maps.

I have also discussed this in an earlier post.
Snowmantest
I have learned a lot since then.

I will address the problems with using a textured wall as a backdrop later.

Cec.
[Oct 25, 2016 11:57:00 PM] Show Printable Version of Post    View Member Profile    Send Private Message    http://cecprojects.wordpress.com [Link] Report threatening or abusive post: please login first  Go to top 
okh
Advanced Member




Joined: May 12, 2013
Post Count: 1286
Status: Offline
Reply to this Post  Reply with Quote 
Re: This is cheating...

@Cec

Yes to pretty much all you say. Thanks for your patience in your testing. Most useful.

First, you will find no objection to your point that the 3D landscapes have great advantages and is inevitable for the high quality rendering. And yes, hiding the levels (Shift-Ctrl-H for non-Mac users) is a must. Having a separate 'terrain' level to hide/unhide is almost always a good idea. Or indeed, keep the terrain in a separate file and copy in for rendering.

So my sky-texture advocacy is really about something else: How to break up the default prairie horizon that looks so misplaced in this part of the world. But, with ever so many shortcomings as you point out.

..the distortion that we have to adjust for:
When stretching it to a dome, the clouds will appear more correct from one point of view - but not if you turn around. But then, clouds and horizons really are two different things. In real life clouds are not glued to the heavenly dome, but pass in relatively straight lines (forget the meteorology for a sec). This means that fluffy clouds high in the sky will look distorted on a background picture. Except maybe when they hover just above the horizon/mountains/treeline.
Using a non-square image will not give the best result, as the sky is actually projected from a square image.
Hmm, this is interesting. My first attempts used panoramas from a camera which indeed were long and narrow. That will look wrong. The sky certainly does need to be stretched up to the zenith. Still, I wonder about the proportions of a good sky texture. In my world, the sky comes in the ratio 4:1 - that is a 360° horizon and 90° up to zenith. Which is so far the ratio I have assumed would be the best. But then, there is the equirectangular projection which will 'compress' the lower part of the image and stretch the upper part of the image. Which probably means a square image could be easier to work with.

I tried with a 3600:900 grid, result below. I am not yet convinced that a square is better, but maybe I am missing something. Views?

What is a slight annoyance, though, is that the 3D window and the photo rendering appears to project differently. Especially for the higher mountains the effect is noticable.

Now, this becomes pretty much a theoretical discussion. For the (inferior)sky-texture technique one needs to work only along a narrow strip at the bottom of the picture. For the upper part, the sky dome, it is better to use a gradient (or a contrast colour to be masked of later). In fact, I suppose the only planetary objects would render correctly above on sky-texture projection - so for a night sky, maybe.

And also - do not get me wrong - this is sidetracking Cec' original issue. So ignore this and scroll far back if you are looking for how to make nice sceneries... :-)

ok


[Oct 26, 2016 10:17:34 AM] Show Printable Version of Post    View Member Profile    Send Private Message    Hidden to Guest [Link] Report threatening or abusive post: please login first  Go to top 
Ceciliabr
Advanced Member
Member's Avatar

Denmark
Joined: Jul 7, 2013
Post Count: 205
Status: Offline
Reply to this Post  Reply with Quote 
Re: This is cheating...

@okh

In real life clouds are not glued to the heavenly dome, but pass in relatively straight lines (forget the meteorology for a sec).This means that fluffy clouds high in the sky will look distorted on a background picture. Except maybe when they hover just above the horizon/mountains/treeline.


Absolutely, but the geometry is already present in the original photo. Our projection should be as linear as possible.

I am not yet convinced that a square is better, but maybe I am missing something. Views?


Well, the distance around zenith is four times the distance to the pole, so a one-by-four ratio is what I also figured would be the best back when I first started to experiment with the rectangular projection.


The reason for choosing a square, is that it leaves me with plenty of headroom at the top.

I have rendered some test images.

One-by-four rectangle.
Field of view: 110



One-by-two rectangle.
Field of view: 110



Square rectangle.
Field of view: 110



And then I have added a sky with mountains:


One-by-four-rectangle.

Image 4096X1024




One-by-two-rectangle.

Image 4096X2048 - sky applied to the lower half. Not adjusted for distortion




Square.
Image 4096X4096 - sky applied to the lower quarter. Not adjusted for distortion.





Any views on what comes out best?



Tent and campfire Sky adjusted slightly for distortion


Cec
----------------------------------------
[Edit 4 times, last edit by Ceciliabr at Oct 26, 2016 2:48:44 PM]
[Oct 26, 2016 2:40:08 PM] Show Printable Version of Post    View Member Profile    Send Private Message    http://cecprojects.wordpress.com [Link] Report threatening or abusive post: please login first  Go to top 
Ceciliabr
Advanced Member
Member's Avatar

Denmark
Joined: Jul 7, 2013
Post Count: 205
Status: Offline
Reply to this Post  Reply with Quote 
Re: This is cheating...

Forgot:

For the upper part, the sky dome, it is better to use a gradient (or a contrast colour to be masked of later).


Actually, for the upper part it's best to use a background colour that matches the sky exactly. The reason for this is that although radiosity is evidently not supported in Sunflow, there will be reflections from the sky on any reflective surface, and especially if there are reflecting water surfaces. So the right colour is very important.

I once tried to substitute the sky with green, in order to use chroma-keying to replace it in the post production, but I ended up with a lot of green reflections and immediately abandoned the idea.

Cec
[Oct 26, 2016 3:06:51 PM] Show Printable Version of Post    View Member Profile    Send Private Message    http://cecprojects.wordpress.com [Link] Report threatening or abusive post: please login first  Go to top 
okh
Advanced Member




Joined: May 12, 2013
Post Count: 1286
Status: Offline
Reply to this Post  Reply with Quote 
Re: This is cheating...

Annoyingly nice illustrations. Actually, you just made the case for sky-texture better than I could have smile
..best to use a background colour that matches the sky...
You are right - now that I think about it, I also tried an off colour that gave all sorts of horrid reflections. Gradients - typically between dark and light blue - work quite well, though.
..reason for choosing a square, is that it leaves me with plenty of headroom at the top....
Yes, that it of course a point - it may be easier to work with.

By the way, in my test texture I have somehow put 10 and not 9 lines to represent the 90° to zenith. While it still illustrates the distortion, it needs adjustment if anyone wants to use it for measuring horizon objects such as a high mountain.

As most smartphones have compass/plumb/level functions (usually a separate app is needed), the angle to the mountaintop can be calculated quite easily as can the alignment of the background texture (starts to the right in the 2D plan, East if compass is due North). That way, it is possible to create a surprisingly accurate horizon around the model which can be completed with other objects close to the building.

But I need to emphasise - that Cec' approach with extensive use of 3D objects is much better for the beautiful renderings where the sun and shades caress the landscape. The rougher texture-sky-treeline approach has a more practical merit: When I work in the 2D plan I want a simple, instant way for the 3D window to display the view around the building. For instance, will it be possible to see mountain X through window Y from my favourite chair.

A rough technique for real life projects where rendering is not the objective, but the point is getting the construction details right through planning with various tools (as mentioned in threads 6162 and 5953).

ok
[Oct 27, 2016 9:09:18 AM] Show Printable Version of Post    View Member Profile    Send Private Message    Hidden to Guest [Link] Report threatening or abusive post: please login first  Go to top 
okh
Advanced Member




Joined: May 12, 2013
Post Count: 1286
Status: Offline
Reply to this Post  Reply with Quote 
Re: This is cheating...

Just to explain the curiosity about how the sky texture is aligned. In this example, with absolutely no rendering ambitions, the aim is to visualize light on a building. Sun path at winter and summer solstice on the background. 2048×512 canvas/texture, degrees and sun path are relatively correct on canvas (the rest of the rest of the sky-texture is based on a couple of random + gradient sky and noon/May Sun).

See the 3D viewer for the full picture. The rendered photo seems more correct than the 3D view - but still off. Would it be useful if celestial objects were correctly placed on the sky texture? Or, more likely, is there a reason for this projection that I am missing? More a question of curiosity than anything else.

ok


[Oct 27, 2016 4:25:14 PM] Show Printable Version of Post    View Member Profile    Send Private Message    Hidden to Guest [Link] Report threatening or abusive post: please login first  Go to top 
Ceciliabr
Advanced Member
Member's Avatar

Denmark
Joined: Jul 7, 2013
Post Count: 205
Status: Offline
Reply to this Post  Reply with Quote 
Re: This is cheating...

@okh


...you just made the case for sky-texture (...)


Which was my intention smile
I'm not trying to talk it down, I'm in fact using sky textures a lot,
although I prefer not to include the horizon. As you can see from the
tent-&-Campfire illustration, even though I did my very best, there's
still a feeling that the foreground is glued to the background – if
you look closely. And the larger the image, the more clearly it will appear.
I actually made a video a year ago, showing how to improve and handle
sky texturing. But I never got around to finishing it with sound and VO.
But it kinda works without.
In case someone wants to see it:

Lef-click to play in a new window or right-cl...e target to DOWNLOAD 16MB

...for real life projects where rendering is not the objective, but the point is getting the construction details right through planning with various tools (as mentioned in threads 6162 and 5953).

Thanks for the link to Geogebra. That is one extremely useful tool. smile

Understanding my views ( as I know you do) it's important to
acknowledge that my viewpoint is from an illustrators perspective.
I'm using SH3D with the sole intention of illustrating, and as a
general rule I want my constructions to be video-compatible (meaning
that all objects, including the horizon, will behave according to the
laws of physics when I move the camera). That's why I cannot have the
horizon fixed to the sky. That's also why I am texturing everything
- even the ground ( and the main reason I would very much like to
substitute the sky with an alpha-channel).

But when my intention is to produce an artistic image only, I use
every technique I know, including fixed horizons on a textured sky as
well as atmospheric layers and transparent pngs og one-sided planes
(like with the fire and smoke in the tent-&-Campfire illustration.

I hope there are other users that can find our discussions as useful as I do.
Thank you for participating and sharing your knowledge. smile

cec
----------------------------------------
[Edit 2 times, last edit by Ceciliabr at Oct 27, 2016 4:53:14 PM]
[Oct 27, 2016 4:51:08 PM] Show Printable Version of Post    View Member Profile    Send Private Message    http://cecprojects.wordpress.com [Link] Report threatening or abusive post: please login first  Go to top 
okh
Advanced Member




Joined: May 12, 2013
Post Count: 1286
Status: Offline
Reply to this Post  Reply with Quote 
Re: This is cheating...

..a video a year ago, showing how to improve and handle sky texturing...
Right, very interesting. And a very good example of the illustrator's eye - it goes to show how SH3D is useful from two very different perspectives. Please, keep the link, I need to study this video again to make sure I understand fully. Really quite amazing how you combine the tools to create such results.
Thanks for the link to Geogebra . That is one extremely useful tool.
Yes, Geogebra is useful. As many with teenagers in the house have found out, Geogebra is a free tool used in school maths many places. To maintain a very minimum of dignity trying to help out with maths homework, I had no option but to teach myself the basics of Geogebra. First thing I could think of was a SH3D discussion about intercepting walls and angles. And it was lots of fun making the wall intercept thingy even if it meant finding out how much trigonometry I had forgotten - and the result hardly impressive. Then, seeing the usefulness of the tool, I went on to use Geogebra to re-teach myself some principles of celestial navigation + finding satellites in geostationary orbit (that is, putting up the satellite dish, which I probably could have done in a fraction of the time by rough guessing). All that said, I highly recommend downloading Geogebra for anyone who used to enjoy maths in school but remember very litte. And for a nuts-and-bolts approach to SH3D construction, it can be a very useful supplement.
..participating and sharing your knowledge.
In this thread, I am certainly the one who is learning from the unrivalled master of beautiful SH3D renderings. I quite enjoy learning something so very different from my day-to-day work. So thank you! ok
[Oct 27, 2016 6:41:39 PM] Show Printable Version of Post    View Member Profile    Send Private Message    Hidden to Guest [Link] Report threatening or abusive post: please login first  Go to top 
VeroniQ
Advanced Member



France
Joined: Mar 3, 2015
Post Count: 268
Status: Offline
Reply to this Post  Reply with Quote 
Re: This is cheating...

Not sure to understand totally either, but thank you for sharing this video, Cec, and, both of you, for this skilled thread.
[Oct 27, 2016 7:37:24 PM] Show Printable Version of Post    View Member Profile    Send Private Message    Hidden to Guest [Link] Report threatening or abusive post: please login first  Go to top 
Posts: 31   Pages: 4   [ Previous Page | 1 2 3 4 | Next Page ]
[ Jump to Last Post ]
Show Printable Version of Thread  Post new Thread

    Get Sweet Home 3D at SourceForge.net. Fast, secure and Free Open Source software downloads
   
© Copyright 2006-2017 eTeks - All rights reserved