Hi,
I am importing a jpeg as an alpha (directly or via Photoshop makes no difference) and I keep getting these tiny spike scattered all over the image. I have tried numerous noise reduction software tools dfine, noise ninja, AutoEye, AutoEnhance the spikes remain.
When I import the alpha I am using Mres 256 as I am trying to preserve the detail.
The spikes remain if I export to .OBJ.
Can anyone help me to remove these?
Thank you in advance,
UA
JPG by definition is a compressed image format. You will ALWAYS have noise, and that noise is especially going to have an impact when dealing with alphas since this channel is best with 16-bit images and JPG’s are only 8-bit. It’s generally a good idea to avoid JPG in the Alpha palette if you can.
What exactly are you doing, though? It’s possible that by understanding your steps we’ll find a workaround.
Hi,
Thank you for your reply.
I am trying to take a photograph and use it as an alpha to create a 3d model.
I have saved the picture as a bmp file and still I see the little spikes.
Is there any way to smooth these things out enmass rather than individually?
Thanks,
UA
Tool>Deformation>Smooth. Just keep in mind that this can also smooth out details you want to keep.
Once a photo is compressed its pretty much all over. If you are scanning a photo or negative redo it as a compression-less file. If you are shooting with a digital see if the camera has a .raw or .tif mode (turn off compression) and convert to 16 bit in PS. If the camera has only a .jpg file type available there is not much you can do. Also never use a sharpening filter - ever - if you want to use the image for an alpha. Use a tripod instead and don’t sharpen in post. If your downloading the photo from the net there is not much you can do unless you can find a .bmp file and even those are usually not of a high enough quality. This may be more info than you needed, but I thought it might help others as well.
I thank both of you for you help.
So, the bottom line if you only have jpegs to work with:
Another question:
What would be the best (as in fast and accurate) method to identify and smooth out these spikes?
Thank you,
UA
Another question:
I converted the jpeg to bmp then converted the bmp to grayscale and I still see the spikes when I make the 3d model.
What exactly are the values in the BMP file that produce the spikes when the BMP is imported as an alpha and converted to 3d.
Are they single pixels that are the extreme values of all ones and all zeros?
UA
Your ORIGINAL SOURCE is JPG. It’s the same as taking a record and re-recording it to a CD. The CD will sound like the record; not like the original artist. You can’t take a compressed format and restore it to non-compressed just by converting it to a BMP. In order to get an artifact-free image you need to start with an artifact-free source. Once it’s been saved as JPG there is no restoring the lost data.
Hi,
Thanks for the reply.
I understand that once the data is gone it is gone.
What I was trying to understand was exactly what pattern of pixel values would cause ZBRUSH to create the spikes.
It looks like the ZB designer’s code is trying to wrap a mesh around a single pixel value. This seems odd since reducing the MRes to 10 still does not average it out.
Since I see it in gray scale and I can see black (0,0,0) in other areas, that means that it most likely is a value at the other extreme of the range.
What would that value be? What type of averaging will help ZB do the right thing?
UA
Have you tried using Photoshop to repair the alpha before even bringing it into ZBrush?
re: PS
I tried a combination of NR strength 10, remove JPEG artifacts and keep detail 1, I have tried at least 5 third party different noise reduction programs. It has to do with ZB’s algorithms because the spikes appear in a full sized image but not when I isolate the area of the picture and crop the picture size to it. The following picture shows the origin of these spikes. They actually appear to be polys that go off into outer space.
Could you provide a sample image that we can test with?
Progress Report
The spikes are a known in the programming world as a feature; (otherwise known as a bug in ZBrush2) they appear when trying to make a 3d mesh from an alpha. The JPEG noise causes extreme changes in intensity and confuses ZB2. I am actually converting JPEG to BMP and using the BMP file to make the alpha. Noise reduction set to max for JPEG artifact removal.
The spikes actually are polygons that are sticking out into outer space; one edge is attached to the mesh while the other is flapping around. As I am sure you all know, all polygon edges should be connected to another polygon edge, just like painting completely around an object. No hanging paint chips allowed.
These features become a problem when you try to convert the .obj file to .stl format. They are considered unmatched edges and therefore an error. This in turn is a problem for your CAD software.
I have not figured out how to remove them with the Transform tool as they continue to hang in outer space almost like they are not recognized by the tools.
As I am a newby to this world of 3d please inform and correct me. All feedback is welcome and appreciated.
UA
Another way of looking at this problem…
Zbrush2 has its own “Hanging chad” problems… 
As I am working trying to figure out how to remove these spikes the thought has occurred to me that I have used up in time and money any advantage that Zbrush 2 has provided for converting jpegs to alphas and alpha skinning. 