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Dear Freesurfer Community,
I use Freeview to render 3D views of overlays on cortical surfaces. For my current processing, the absolute scale of the overlay map is important, and this absolute scale is distorted / marred by the shading that Freeview adds due to its default light source. (E.g., the top of the image is lighter than the bottom.)
My question is this: is there any way to change the default light source of Freeview? I would prefer to use a uniform ambient light that did not cast any shadow, such that each pixel’s rendered intensity was exactly correlated with the absolute value of the visualized overlay in that pixel.
If this is not possible, a point light source “at infinity” pointing directly into the plane of view might also suffice, since I believe it would produce a uniform illumination on a spherical base hemisphere. (I could be wrong here.)
One final note: ideally this method would be possible to achieve by the command line, or failing that, to manually change in the GUI such that the setting would be preserved upon quitting and restarting Freeview.
As always, any help is much appreciated. If someone happens to know that this functionality is absolutely not available, I would certainly like to know that, too.
Thanks in advance.
Sincerely, Sam Johnson Postdoctoral Scholar Brain and Education Lab, Stanford University GSE
Hi Sam,
I’ve added a flag called “no_shading”. It is a flag for the surface, not for the light source. It can be applied from the command-line like this:
freeview -f lh.inflated:no_shading=1
You can download the latest build of freeview here: https://surfer.nmr.mgh.harvard.edu/fswiki/UpdateFreeview
Best, Ruopeng
On Mar 28, 2022, at 6:45 PM, Sam Buck Johnson <samjohns@stanford.edumailto:samjohns@stanford.edu> wrote:
External Email - Use Caution
Dear Freesurfer Community,
I use Freeview to render 3D views of overlays on cortical surfaces. For my current processing, the absolute scale of the overlay map is important, and this absolute scale is distorted / marred by the shading that Freeview adds due to its default light source. (E.g., the top of the image is lighter than the bottom.)
My question is this: is there any way to change the default light source of Freeview? I would prefer to use a uniform ambient light that did not cast any shadow, such that each pixel’s rendered intensity was exactly correlated with the absolute value of the visualized overlay in that pixel.
If this is not possible, a point light source “at infinity” pointing directly into the plane of view might also suffice, since I believe it would produce a uniform illumination on a spherical base hemisphere. (I could be wrong here.)
One final note: ideally this method would be possible to achieve by the command line, or failing that, to manually change in the GUI such that the setting would be preserved upon quitting and restarting Freeview.
As always, any help is much appreciated. If someone happens to know that this functionality is absolutely not available, I would certainly like to know that, too.
Thanks in advance.
Sincerely, Sam Johnson Postdoctoral Scholar Brain and Education Lab, Stanford University GSE _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edumailto:Freesurfer@nmr.mgh.harvard.edu https://mail.nmr.mgh.harvard.edu/mailman/listinfo/freesurfer
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Thanks, Ruopeng!
Now that I’ve tried the latest version, I can say that your added flag works just as I was hoping. Thanks so much for taking the time to accommodate this particular request – I can only hope others may eventually find it useful as well.
Sincerely, Sam
From: freesurfer-bounces@nmr.mgh.harvard.edu on behalf of "Wang, Ruopeng" RWANG4@mgh.harvard.edu Reply-To: Freesurfer support list freesurfer@nmr.mgh.harvard.edu Date: Monday, April 4, 2022 at 7:48 AM To: Freesurfer support list freesurfer@nmr.mgh.harvard.edu Subject: Re: [Freesurfer] Advice: changing Freeview light source?
Hi Sam,
I’ve added a flag called “no_shading”. It is a flag for the surface, not for the light source. It can be applied from the command-line like this:
freeview -f lh.inflated:no_shading=1
You can download the latest build of freeview here: https://secure-web.cisco.com/1REpI-tnquGty_G_RLtsEs7LoXcZgyjBJr5TaY5fnF_G8kc...
Best, Ruopeng
On Mar 28, 2022, at 6:45 PM, Sam Buck Johnson <samjohns@stanford.edumailto:samjohns@stanford.edu> wrote:
External Email - Use Caution
Dear Freesurfer Community,
I use Freeview to render 3D views of overlays on cortical surfaces. For my current processing, the absolute scale of the overlay map is important, and this absolute scale is distorted / marred by the shading that Freeview adds due to its default light source. (E.g., the top of the image is lighter than the bottom.)
My question is this: is there any way to change the default light source of Freeview? I would prefer to use a uniform ambient light that did not cast any shadow, such that each pixel’s rendered intensity was exactly correlated with the absolute value of the visualized overlay in that pixel.
If this is not possible, a point light source “at infinity” pointing directly into the plane of view might also suffice, since I believe it would produce a uniform illumination on a spherical base hemisphere. (I could be wrong here.)
One final note: ideally this method would be possible to achieve by the command line, or failing that, to manually change in the GUI such that the setting would be preserved upon quitting and restarting Freeview.
As always, any help is much appreciated. If someone happens to know that this functionality is absolutely not available, I would certainly like to know that, too.
Thanks in advance.
Sincerely, Sam Johnson Postdoctoral Scholar Brain and Education Lab, Stanford University GSE _______________________________________________ Freesurfer mailing list Freesurfer@nmr.mgh.harvard.edumailto:Freesurfer@nmr.mgh.harvard.edu https://secure-web.cisco.com/1zVUQAzG9IU6yXsLa-dh5B8VEXIvO6JbU1PKMewfXoPMF7w...
freesurfer@nmr.mgh.harvard.edu
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Sam Buck Johnson -
Wang, Ruopeng