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jenny_wui

Constructing 3D model from Disc Image Files

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L. Spiro    25638

You will have to be more specific than that.

Is there something you want to mention about the significance of them being on a CD (or an image of a CD) rather than on a harddrive?  Is this about the image format itself or the format of the 3D models inside it?

In what format are the files?

 

 

L. Spiro

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Saurabh Torne    220

yeah, i guess the 3dmodel files are on a disc. Totally a mix of composition.

 

Image of a CD is called so, but its a ditto copy of the cd content, but in a file. If thats what your looking for Jenny_wui, then you gotta

a) burn it to a disc or

b) mount it on a virtual CD drive.

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jenny_wui    200

The file type is written as Disk Image File. I have 90 X-sections i.e.  90 Disk mage Files. All I am concerned about constructing 3D model from the images. I would prefer surface-based rendering. I have never dealt with these kind of images. Please provide me with some suggestions.

 

Thanks again in advance.

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jenny_wui    200

Another thing to note when I try to burn to disc, it shows, the extention of file is img. When I try to burn a particular image to disk, it shows, the selected disk image file is not valid.

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BitMaster    8651
If you are working on Windows, the visible file type is solely dependent on the file extensions for nearly everything there, including the more descriptive text like "Disk Image File". While it is not common for the average user, file extensions often have quite a bit of overlap or files are simply named wrongly.

The actual file extension would be slightly more helpful but probably won't be enough to solve your problem. Where are those files from? Is there any documentation included?

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jenny_wui    200

I received a folder containing  a set of  cross-sectional images of coronary artery acquired by IVUS pull-back. It is said that each image is stored as raw format  where the size is 256 pix by 256 pix with 1 byte per pixel (i.e., 65536 bytes per image).

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BitMaster    8651
Opening the images should be trivial with this description. Using those images to reconstruct a 3D model is not, unfortunately. I'm not well enough versed in the area to comment but I fear there will be no simple solution and you will need to spend quite a bit of time acquiring rather specialist knowledge.

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BitMaster    8651
Open the file in binary and read the first 256 bytes. Now you have the first line or row of the image in grayscale (0-255). Whether it is a line or row will depend on whoever created the image and is not documented in the text you posted. Neither is documented if that line/row is the top/left or bottom/right line/row. Read the next 256 bytes. Now you have the next line/row of the image in grayscale.

I'm afraid the question is far too fuzzy to answer in a more meaningful way. What do you know? What causes you difficulty? What have you tried? Edited by BitMaster

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JTippetts    12970
As far as reconstructing a model from the data, your best bet is to go with an algorithm such as marching cubes or marching tetrahedra. They are algorithms intended to construct a surface from a data set, where each element in the data set represents a material density function. The algorithm can reconstruct the surface (or, at least, an approximation) at a given density threshold.

Alternatively, if you just need to visualize the 3D medium represented by the scans, you could do ray tracing of the data set. Emulate casting rays into the density medium, and assign different opacity, color, etc... to the various densities represented by the function. You integrate the ray as it communicates through the medium, accumulating opacity and color as you go until the total opacity becomes solid. By mapping densities to different material settings using some sort of look-up or other mapping, you can "peel back" layers of the density function to expose different internal structures without having to go through the process of re-constructing surfaces through marching algorithms. With more complicated ray-casting, you can do things such as self-shadowing, light scattering, etc... to get a better visual representation of the medium

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jenny_wui    200

Hi, I have been able to open the file. Now I want 3D surface-based rendering i.e. the model should be polygonized. As it is difficult for me to write some algorithm like marching cube , could somebody provide me some further suggestions? Thanks.

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First hit on google for "marching cubes source code"

 

http://paulbourke.net/geometry/polygonise/

 

Another alternative (at least for quick visualisation, doesn't make 3d geometry) is to render a point cloud i.e. camera facing sprites/billboards which should be easy to get you going.

 

EDIT: I'd go point cloud first, then just cubic voxels, then marching cubes dem voxel asses.

Edited by Paradigm Shifter

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jenny_wui    200

I really like your approach. I have also some theoretical knowledge on volume-based and surface-based rendering. I shall be able to develop the point clouds and later the voxelized model myself. But from there while constructing iso-surface using marching cube algorithm seems a bit difficult to me as the algorithm has too many options for each voxel.  I need some tutorial help which shows both volume-based (ray tracing) and surface based reconstruction (marching cube) for the same simple model from which I shall be able to understand how to work for my model. If there any related website, please let me know.

 

Thanks every body for the suggestion.

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