[Chimera-users] Saving image and rendering

Ibrahim Moustafa I.moustafa at psu.edu
Tue Jun 23 12:26:34 PDT 2009

Thanks Eric for the reply.

  Actually, I¹m not using transparent surfaces. The image I tried to make is
a normal cartoon model.

  For the ³glossy lighting² option: the button with the default ³normal² is
inactive. How to turn it on? I could not figure it out.


On 6/23/09 1:24 PM, "Eric Pettersen" <pett at cgl.ucsf.edu> wrote:

> On Jun 22, 2009, at 3:53 PM, Ibrahim Moustafa wrote:
>>  Dear Chimera team,
>>     Recently, I have some trouble saving images with POV-RAY option ³true².
>> The process of rendering is too slow (both on the mac and windows version).
>>  To give the feeling of how slow: rendering an image with 1700 lines takes 7
>> hrs (with quality 9 in pov-ray options) and 2 hrs (quality 5). I used to get
>> the images rendered much faster than that (with older versions; however, I¹m
>> not exactly sure of when I started to see such a slow rendering behavior).
> I'm guessing you're using transparent surfaces.  We've made improvements in
> the fidelity of translation of transparent colors between Chimera and POV-Ray
> since the 1.3 release.  In 1.3, the transparent colors were much darker than
> they appeared in Chimera.  This change increases the rendering time because
> the amount of supersampling that POV-ray performs depends on how much color
> variation there is in the image and the new scheme provides a lot more
> variation than its uniformly dark predecessor.  One example I tried produced
> slightly more than a factor of two in rendering times between the 1.3 version
> and the current daily build.
> Now, if you're rendering such a high-resolution image you don't really need as
> much effort expended on each individual pixel as you do for a smaller image.
> I find that if I increase the "Antialias threshold" POV-Ray option from 0.3 to
> 1.0 then I get an almost unchanged image in approximately the same time as as
> the 1.3 version required.  You might even be able to go higher than that and
> still get a good image.
>>    There is another related problem but only with the windows version: If I
>> want to save an image, with depth cue, using the fast mode (POV-RAY false),
>> the image output lacks any depth used in the model, with poor quality and
>> darker than it should be. Somehow, the camera orientation is messed. In
>> addition, the depth cue will be no longer available for the rest of the
>> session (I have to restart over again). To get the depth cue I want, I need
>> to turn the POV-RAY option ³true²....but then too slow to create a good
>> figure.
> I understand that Greg (who works on this code) recently made some
> depth-cueing related bug fixes.  Please try the very latest daily build and
> see if you still get this problem.  If you still do then please use
> Help->Report a Bug to send us a bug report which will automatically include
> detailed information about the system you're using.
>>    I¹d appreciate any comment or explanation from Chimera people; and what is
>> the best way to overcome this problem?
> An alternative to ray tracing is to turn on "glossy lighting" (from the
> Lighting tab of the Side View).  That may look good enough for what you want
> and works with Chimera's non-raytraced image saving.
> --Eric

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