Texture of collapsed towers

[jb.barreau]

Hello,

My team and I have a point cloud of a castle and we would get a uniform texture to redraw stones. The problem is that these towers are very collapsed and seem neither cylinders nor cones. I have no idea of strategy to adopt in order to obtain a conclusive result.

Thank you in advance for your answers and-have avery good day.

[daniel]

Sorry I didn't understand what you are trying to do! Can you post a picture maybe? And more information?

[Dimitri]

Tu peux aussi m'appeler Jean-Baptiste, je pourrais vous dire si Cloudcompare pourra solutionner votre problème.

A+

[jb.barreau]

Hello!

Overall, we have a point cloud and we want to get a texture to draw, with illustrator, this kind of thing:

Do you think this is possible?

Dimitri, we try to call you as soon as possible :-)

[cdordoni]

I think the easiest way to do it would be to get it into a 3d rendering program and set up multiple views around the object using an ortho rendering camera to eliminate perspective. You will get distortion/mismatch at the edges of the images due to the change in the direction of view.

A more difficult method would be to create a low resolution object with UV coordinates and "bake" all the high frequency detail into texture, normal and depth maps. These texture maps could then be manipulated in Photoshop or similar to produce a line art or drawing effect. The low resolution object would have to be designed in a way that when it flattens (UV unwrap) it generates a panoramic like image. I've seen similar things done with ZBrush, and Blender. I can't explain exactly how to do it but I'm sure you could get some assistance over on the Pixologic and Blender forums. Other 3d software might be able to handle this as well. There will still be some distortion or compromise with this method, but I think its better than the first method above.

[daniel]

Oh now I understand. You want to 'unwrap' the cloud along the wall lines? And get a single '2D' cloud.

There has been a similar question recently. CC can do this if you can draw a 2D polyline (from above) corresponding to the walls baseline along which to unwrap the cloud. However this function is now accessible to the user (it is used internally by the 'Extract sections' tool). Can you share the point cloud with me? (cloudcompare [at] danielgm.net)

[cdordoni]

Daniel,

I saw your reply to the Unroll - Parabolic thread; however, here you indicate you have added this functionality. Is coming in a future release?

[daniel]

Indeed, it's working on my side :D

I just need to compile the project and put it online. I'll post a new message when that's ready.

[cdordoni]

Thanks, that could be very useful, and a lot faster than going through Zbrush, Blender or other software.

[daniel]

Okay, the tool is ready. This is a neat addition (especially as it was already there and I hadn't to do much ;).

It is based on the 'Extract sections' tool (http://www.cloudcompare.org/doc/wiki/in ... t_Sections). Therefore you might want to learn a bit how to use this tool first. Basically it lets you load or draw 2D polylines on top of your cloud (you can choose the vertical direction as being X, Y or Z which is the default). Then you can either extract the points close to these polylines, or extract the contour of the cloud in the 2D planes defined by these polylines.

And now you can 'unfold' the cloud along a polyline!

Here is a rapid walkthrough:
1. prepare your cloud: I removed the vegetation for this demo, and I made sure the walls were almost vertical.

cc_cloud_unfolding_origin.jpg (106.06 KiB) Viewed 15429 times

2. Start the 'Section extraction tool' and start drawing the wall baseline right away (as a polyline). Don't forget to right click when you've finished to draw the polyline and then leave the 'polyline edition' mode by clicking on the first icon:

cc_section_extraction.jpg (25 KiB) Viewed 15429 times

3. Click on the 'unfold' icon.

unfoldSmall.png (210 Bytes) Viewed 15429 times

4. CC will ask you to specify a maximum distance to the polyline (this is to get rid of points very far from the baseline, but you could of course set a very big distance if you want to be sure to keep all the points of your cloud). And that's it. All unfolded clouds will be exported to the main DB (you can use the 'Section extraction' tool on multiple clouds at once). Just close the tool to access them.

cc_cloud_unfolding_2.jpg (201.8 KiB) Viewed 15429 times

P.S.: you can also save the polyline for later use.

The beta version is here: http://www.cloudcompare.org/release