VMD-L Mailing List

From: John Stone (johns_at_ks.uiuc.edu)
Date: Tue Mar 02 2021 - 15:40:11 CST

Hi,
  Josh is correct that a very critical issue for getting so-called
"transparent backgrounds" is choosing an image file format that supports
an "alpha channel". To get the desired outcome, both the rendering engine
and the image file format have to fully support alpha channel output.

POV-Ray and the NVIDIA OptiX GPU-based version of Tachyon implement this
feature in the renderer, and both of them support output to PNG files.

At present, the CPU version of Tachyon doesn't yet implement alpha channel
output mode as I just haven't had time to rewrite the affected parts
of the code to add it yet. It was comparatively easy to add to the GPU
version of the code without affecting performance.

Best,
  John

On Tue, Mar 02, 2021 at 09:17:59PM +0000, Vermaas, Josh wrote:
> Hi Felipe,
>
>
>
> .tga files can't do transparency. .png files can though, and it looks like
> POV-Ray is being told to write a .png based on your command, so I don't
> know what's up, since you also have the +ua argument folks say is
> essential:
> [1]http://news.povray.org/povray.general/thread/%3C59dbba2b%40news.povray.org%3E/
>
>
>
> For my own rendering purposes, I use OptiX, with the options John laid out
> here:
> [2]https://www.ks.uiuc.edu/Research/vmd/mailing_list/vmd-l/31053.html
>
>
>
> -Josh
>
>
>
> From: <owner-vmd-l_at_ks.uiuc.edu> on behalf of "Pacci Evaristo, Felipe
> Fabricio" <felipepacci_at_gmail.com>
> Date: Tuesday, March 2, 2021 at 3:18 PM
> To: "vmd-l_at_ks.uiuc.edu" <vmd-l_at_ks.uiuc.edu>
> Subject: vmd-l: Render image background-free
>
>
>
> Hi there,
>
>
>
> I've been trying to solve this problem for a while now. I'm on macOS
> Catalina. I've been trying to render an image background-free on VMD. I've
> been trying to use POV-Ray for that. I found tutorials where people have
> used the following line in the Render Command box in the GUI interface
> (except for the link to the POV-Ray executable):
>
>
>
> '/Users/felipepacci/Downloads/PovrayCommandLineMacV2//Povray37UnofficialMacCmd'
> +W%w +H%h -I%s -O%s.png +D +X +A +FN +UA -res 1600 900
>
>
>
> This render does produce a .pov file; however, when I try to render it
> into a .tga file in POV-Ray, the output .tga image still contains a
> background. Am I missing something really obvious here?
>
>
>
> I'm open to other methods that don't include POV-Ray to generate my
> background-free image.
>
>
>
> Thank you beforehand for any help provided,
>
>
>
> Felipe Fabricio Pacci Evaristo
>
> Mobile: +1(773)569-2978
>
> Email: [3]felipepacci_at_gmail.com
>
> Skype: felipepacci
>
> References
>
> Visible links
> 1. https://urldefense.com/v3/__http://news.povray.org/povray.general/thread/*3C59dbba2b*40news.povray.org*3E/__;JSUl!!DZ3fjg!sXtoTZWxyVOoJFd6yhSYMYD5WGQ5FlFdp19IBsiFoenHmvXykCSgQMAX7NQdqZc1eQ$
> 2. https://www.ks.uiuc.edu/Research/vmd/mailing_list/vmd-l/31053.html
> 3. mailto:felipepacci_at_gmail.com 

-- 
NIH Center for Macromolecular Modeling and Bioinformatics
Beckman Institute for Advanced Science and Technology
University of Illinois, 405 N. Mathews Ave, Urbana, IL 61801
http://www.ks.uiuc.edu/~johns/           Phone: 217-244-3349
http://www.ks.uiuc.edu/Research/vmd/