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Messages - bigben

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16
General / Re: Aligning top and bottom of an object
« on: March 09, 2016, 03:32:45 PM »
The method outlined by James should work fine.  If you try this again.  Use a completely different background (so the backgrounds in the 2 chunks won't align to each other. For the upside down shot, prop the object up so that it isn't touching the background. That should make removal of the background easy.

17
If you're using TIF you can store the mask in the alpha channel.  Doesn't stop if the image has no alpha.

18
General / Re: Canon 1200D experiences....
« on: February 27, 2016, 12:09:26 PM »
Your typical reviews on dpreview should suffice for most decision making... looking for sharpness, low noise (at the typical ISO range you're working at), buffer speed (if capturing continuously and timing is critical).. other than that your specific applications may have other requirements, but then it's just a case of making sure those are met.

19
General / Re: Room scan - Getting rough uneven walls on mesh
« on: February 27, 2016, 02:39:25 AM »
Pretty standard for lack of surface detail.  Notice that the targets and a small area of wall around them are smooth.

20
General / Re: Does image orientation matter?
« on: February 21, 2016, 05:21:42 AM »
Are you masking out the background?

21
General / Re: memory and masked objects
« on: February 14, 2016, 12:46:53 AM »
It's based on the number of points.  Masking will reduce the number of points, but quantifying how much that reduction is, or how many points will be generated in the first instance depends on many other factors.

File format of images only affects how much disk space they occupy. Memory consumption is based on pixel count and bit depth making file format irrelevant in that case.

22
General / Re: Camera-based chunk alignment/ merging chunks
« on: February 13, 2016, 06:51:37 AM »
Well it took a while, but I created a point cloud from all of the images in this set which took a week to align and a few days to produce a dense cloud.  The result was, as expected, pretty good. http://files.digitisation.unimelb.edu.au/potree/pointclouds/ricketts-test2.html  but this is about as long as I'm prepared to have a machine processing a single chunk.  I had thought of aligning one chunk, exporting the last few cameras and importing them into a new chunk with fixed positions before adding the extra images.  Given that I'm using fisheye lenses and the subject is relatively complex, a small shift in camera position can create very noticeable differences. 

Still interested to hear any suggestions.

23
General / Re: Spherical camera rig (not nodal)
« on: February 12, 2016, 08:19:19 AM »
For camera stations you treat each photo set as a single camera.  What size images/fov of lens?  The fact that you have some depth being calculated suggests that there is a reasonably amount of parallax (as you'd expect with that many cameras) so it may not be optimal to treat them as a camera station as it would most likely result in image distortion.  As a general rule I use a camera separation of 0.5X - 1X the distance of the nearest surface (often camera to ground)... and yes that's a lot of images.

Personally I'd use the multiple cameras on a pole mounted rig so that you have multiple heights. You don't have to cover 360° each time, but you do have to move around a lot.

24
General / Re: Decimation and "fixed length per point"
« on: January 29, 2016, 11:05:04 AM »
Just generate a DEM instead of a mesh?

25
General / Re: 3D Printing file standards? pre-flight checklist?
« on: January 29, 2016, 10:57:59 AM »
Meshmixer started as more of a 3D sculpting app that grew additional features pertaining to 3D printing. Autodesk now use it as a "printer driver" for some of their design apps. We ran a modest printing service at my uni for a couple of years and this became our tool of choice for checking clients' models. 
Good analysis and repair tools.
If the model is a complete mess it has a "shrink wrap" function that basically wraps a new mesh around the model to create a lower res but watertight mesh.
Centre of gravity calculations (will it stand up)
Tools for shelling and placing drainage holes

For mesh resolution it depends on the printer.  For high res printers we've used 100mb stl files without any problem, but other printers can freak out. Check the requirements with your print service. Meshmixer started to freak out a bit if we gave it more tha 5million polygons so that was our de facto max.  Others use ZBrush which is very good but a bit quirky to get used to.

26
General / Re: Photoshop camera raw export parameters... what matters?
« on: January 17, 2016, 02:56:44 PM »
You'll get a few different answers for this... ;)

Camera exposure as high as possible without blowing highlights on subject (ignore the sky)

ACR settings are typically (for objects, scenes not orthomosaics):

Basics
Blacks: 0
Recovery: 0 to 10 (if I pushed exposure a little too far)
Fill Light: 30 to 50 (overcast-sunny)
Contrast: -20 to -40 (overcast-sunny)
Settings will vary depending on the subject matter/lighting conditions... ie. use common sense.

Lens correction with profile if available
Distortion: 0
Vignetting: 100
Remove chromatic aberration

ProPhoto RGB

No sharpening. Occasionally do some noise reduction but only IF I was desperate enough to use max ISO... Set visually then reduce settings to 2/3.

27
General / Re: What causes these random bubbles/disks in point cloud?
« on: January 15, 2016, 05:25:57 AM »
Waves move.  For each flight path the waves between consecutive frames are similar enough to align/mesh, but between flight paths they are too different... so you're getting part of your mesh from one flight path, and part from the other.  But because the waves have moved between shots the distance won't be accurate and you can get different hieghts for each flight path.  If correct, this could be confirmed by selecting points in each section and filtering the cameras.

28
General / Re: corlor correction within a single image
« on: January 13, 2016, 08:58:39 AM »
I usually do this externally using Adobe Bridge/ACR/Photoshop as part of an image preparation. Either manually set the vignetting correction or use a built in profile if it has one.  This includes any colour correction/contrast tweaking/masking etc...

29
General / Re: Street View Image masking
« on: January 13, 2016, 08:54:18 AM »
I usually do this sort of thing externally using a Photoshop action using a colour range selection to create an alpha. Depending on your scene this may also mask out areas of interest. If there's a lot of variation I set the colour range selection to manual input so it sets up the selection but gives you an opportunity to tweak it.

30
You need to have the cameras in a folder so that you can set it as a camera station ... tells PS that all cameras in that folder have the same position.

Photogrammetry requires images from different positions... so while you have images of different parts of the room they're all shot from the same position so there is no way to calculate depth info.  The points you see in the pointcloud are all at the same distance from the camera location and actually indicate vectors from the camera position to the point.

You can use multiple camera stations, but this requires a large number of images as each camera station is only equivalent to a single camera regardless of how many images are in it.

You can export a panoramic image from a camera station. It will be a 360°x180° equirectangular panorama at the full resolution of the source images. There are no options for setting the resolution of the panorama AFAIK.

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