From: Vermaas, Joshua (
Date: Wed Sep 07 2016 - 13:20:54 CDT

I stand corrected. :) Tachyon does indeed have that behavior, but the
OptiX path doesn't, which was the one I checked first. My bad!

On 09/07/2016 12:13 PM, John Stone wrote:
> It depends on which renderer you use. If you use Tachyon, you should
> get a fully saturated color for high ambient values. The OpenGL
> renderer takes a shortcut there for performance reasons, whereas
> Tachyon does not...
> Cheers,
> John
> On Wed, Sep 07, 2016 at 05:53:01PM +0000, Vermaas, Joshua wrote:
>> Hi John,
>> I thought so too, but what you get for a pure ambient material is
>> something gray, as though the colors aren't being applied with ambient
>> light. Adding in some diffuse character appears to be essential to
>> getting color that isn't white, black, or some shade of grey. Since
>> diffuse responds to the angle of incident light, I don't think VMD is
>> currently capable of colorful but perfectly flat shading.
>> -Josh
>> On 09/07/2016 11:32 AM, John Stone wrote:
>>> Hi,
>>> Aside from running Tachyon with the special flags, you could also
>>> simply use a special material and disable shadows, and possibly
>>> use orthographic projection get a flat unshaded 2D-like appearance.
>>> If you make a material that has the diffuse and specular coefficients
>>> set to zero, but retains a non-zero "ambient" term, when you render with
>>> Tachyon or TachyonInternal you should get what appears to be an unshaded
>>> rendering. Let us know if you have further questions.
>>> Cheers,
>>> John Stone
>>> On Wed, Aug 31, 2016 at 04:37:42PM -0400, Ky Wildermuth wrote:
>>>> Eric,A
>>>> What works for me is rendering with Tachyon and choosing the option
>>>> -lowshade such as in the example below:
>>>> render Tachyon $filename "/vmd/vmd-1.9/lib/tachyon/tachyon_LINUXAMD64"
>>>> $filename -lowshade -format BMP -o $filename.bmp
>>>> This is a low quality rendering option that produces no shading at all (at
>>>> least for the systems I have been working with). I am not sure if it would
>>>> make a difference but I render the images using lights 0 and 1 on (and all
>>>> others off) and I use the surf representation.
>>>> I use this to quantify areas of selections based on color via a python
>>>> computer vision script and it works well to identify entire selections of
>>>> a specific color. You can try some other rendering options if this isn't
>>>> exactly what you are looking for; there is a comprehensive list of Tachyon
>>>> options on a previous post that you can find here:
>>>> [1]
>>>> I hope this helps.A
>>>> -Ky
>>>> On Wed, Aug 31, 2016 at 2:52 PM, Eric Smoll <[2]>
>>>> wrote:
>>>> Hello VMD community,
>>>> VMD representations of chemical systems in with a style like VDW shows
>>>> complex shading. This shading is dependent on the lighting scheme and
>>>> shows the curvature of each atomic sphere. I am interested in generating
>>>> an image with no shading. If the system contains two types of atoms
>>>> coloured red and blue, the image should only contain pure red and pure
>>>> blue at any viewing angle. I want an image with no contrast between
>>>> atoms of the same type.
>>>> Can this be done in VMD? If not, does anyone know of a visualization
>>>> tool that might be able to accomplish this?
>>>> Best,
>>>> Eric
>>>> References
>>>> Visible links
>>>> 1.
>>>> 2.