Exporting 2D graphics with NO size limit.
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This tutorial arises from a thread http://forums.sketchucation.com/viewtopic.php?f=79&t=26474 started by me a few days ago asking if anyone could tell me what the limit was on 2D export size as my machine regularly crashed past the 10,000 pixel width mark.
This lead me to an older thread http://forums.sketchucation.com/viewtopic.php?p=141587 started by Pixero last year concerning size limits on 2D export. Pixero's thread was basically a test to try and establish exactly the limit on size for a two D export by asking other users to test an export of the same image. The results varied from about 5000 to 10,000 pixels wide.
As a Mac user I discovered that, by turning off transparency, and loading a freshly opened file into a freshly open SU I could get up to 14000 pixels width using 2D Export in the File menu. This prompted one user, Gaieus, to comment "Sigh … I cannot even dream about exporting at such large format with AA on (even with AA off I guess)"
So he set me thinking and I did some playing and discovered a work around. Like all work arounds it is a bit clunky …. but it does work. Using it I have already exported the same test image used by Pixero's research at a hefty 30,000 pixels wide and, in theory, the technique is able to export to any size without limit.
In the 2D world if you want to print an image larger than your printer can handle you do it by tiling. You break the image down into smaller 'tiles' and print them individually and then physically reassemble them.
I wondered if the same could be applied to a 2D export from SU. SU exports the part of the image showing on the screen. So if you were to zoom in to your model until it is much larger than the screen, the portion showing on the screen would become a tile. If you were zoomed in to roughly four times the size of your model, for example, you could pan to show the top left quarter of it on screen and export that screen, then pan to the top right quarter of the model and export that screen, and so on for the two lower quarters. Then you simply assemble your four exported tiles in Photoshop.
Now any SU user worth his salt is going to realise immediately that this simply can't work. When you pan in 3D you change the viewpoint and your four exports quite simply would not match. Tiling only works when panning a flat 2D image whose viewpoint does not change.
It suddenly occurred to me that there is a special circumstance under which SU will treat a 3D model as a 2D plane and enable you to pan and zoom it exactly as if it were a flat 2D image and that is when in Match Photo mode. After some trial and error I have come up with this technique:
- Load your model and adjust it to roughly the viewpoint you want and let it fill the screen but with a bit of "air" all around it. (I am using the same http://sketchup.google.com/3dwarehouse/details?mid=d218e86bdbc5ab2b972ec726e7a08cca&prevstart=72 model that Pixero used for his tests). Here is my starting view.
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Open the Match Photo dialogue and load a photo. ANY photo will do, wife, girlfriend, landscape, its completely irrelevant what the subject is, but Match Photo needs something to load to work. (This is not a Match Photo tutorial. If you are not familiar with it then dive into Help and find out about it first.)
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Your model view will be reset with the horizon centered and a fairly wide field of view. Your photo will be behind it. (You can see a glimpse of my grandson's hair top left.) You don't need this photo any longer. It has served its purpose, which was quite simply to launch the Match Photo tools. It is now a distraction. So set the Opacity slider in the Match Photo dialogue to zero.
- Now use the Match Photo controls in the model window to reset your view. You will need to use the origin control, horizon control, and the red and green axis vanishing point lines. It is not very instinctive and to begin with, until you start to get the knack of what does what, it can be frustrating and fiddly. But you soon get the hang of it. Here is my view view re-set using these controls. (One small caveat here. SU marks the edges of the photo with red lines. They pass behind the model so are not too disturbing but they will get exported with your image so you need to either set your model well within them so they are cropped in the final image or expect to spend a little time removing them in your final composite.)
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Once you are happy with your view click Done in the Match Photo dialogue box. The view will be saved as a Scene using the name of the photo. If you're not familiar with Scenes then check your Help files.
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Now comes the fun part ……. WITHOUT TOUCHING THE ORBIT TOOL (OR 3D NAVIGATOR if you use one) …. Use the Pan and Zoom tools ONLY to move your image. If you accidentally use another navigation tool click on the Scene button at the top of the modeling window to restore the photo matched scene you set up.
Now something quite unexpected happens when you move your model around with Pan and Zoom tools in a matched photo scene. SU treats the model as a flat 2D plane! It no longer moves in 3D space but is simply panned and zoomed as a 2D image. You can think of it as being glued to the back of your screen.
Now we can zoom right into the model and by moving it around export multiple 2D screens of different portions of it … or, in other words, tile the image.
How many tiles you need will depend on how large an export your particular machine can handle. The only way to find out is by testing an export until you find the limit for your machine for a single tile and then do the maths for the number of tiles needed for the final image size you want.
Using this technique I exported this image as six tiles to produce, allowing for overlaps, a final image 30,000 x 18,000 pixels! At a high print density of 300 DPI that's 2.5 x 1.5 metres (or 8' 4" x 5'). Bearing in mind that, if you were making a print for an exhibition that wasn't going to be viewed from close up, a density of 150 DPI would probably be fine you would double that size to 5 x 3 metres or 16' 8" x 10 ft. More than enough for most purposes I would imagine.
So that's it. In theory there is absolutely no limit to the size you can export this way beyond what you can load into your bitmap editor for the final assembly.
Ironically I am not an experienced SU user, so if anyone can see ways to improve on this please don't be shy. I would love to know.
Have fun.
David Mac
BTW In the course of the previous thread Gaieus mentioned that export with transparency is a luxury only available to Mac users. So as a companion to this I am posting a technique for exporting an Alpha channel of your model where SU's own export does not support it. It is under the title "Creating an Alpha mask of your model for 2D Graphic export."
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Very clever! Thanks for the tutorial
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And thanks again, David, for taking your time to fully elaborate the method. I will also fiddle around with it (maybe even play around with some rendering plugins to see how this can get through).
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@gaieus said:
And thanks again, David, for taking your time to fully elaborate the method. I will also fiddle around with it (maybe even play around with some rendering plugins to see how this can get through).
The only Renderer I have any experience of is IDX Renditioner it has an absolute size limit of 4096 pixels width or height. No work arounds there. Trying to tile renders produces unmatched renders from tile to tile.
David Mac
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Good tutorial, thank you David.
And no need to use Match Photo, just set camera and check the menu camera-->two point perspective......then get your step6, right?
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@arc said:
And no need to use Match Photo, just set camera and check the menu camera-->two point perspective......then get your step6, right?
Ummmm ..... Yes ......
......... and ....... No ........
Two point perspective does seem to have the same 2D qualities when manipulated with same Hand/Zoom toolset. I hadn't appreciated that. But .......... unless I am missing something here ........ it limits you to two point perspective!
The example I showed is far from two point ......... Match Photo works for any perspective ......
That said and done, I do often use two point perspective and this is a great shortcut for that situation. Thank you.
David Mac
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