[Radiance-general] rpict image rendering problem

[Ji Zhang]

Dear Greg and Chistopher, Thank you very much for your detailed advices! -
Ji


On Tue, Apr 26, 2011 at 11:32 PM, Greg Ward <gregoryjward at gmail.com> wrote:

> Hello Ji,
>
> I won't address all of your issues, but you seem to be laboring under a
> basic misunderstanding regarding image file names and types.  Simply
> specifying a different suffix doesn't cause Radiance to write out whatever
> format file you choose.  Rpict and most Radiance tools that don't start with
> "ra_" output only to Radiance RGBE (.hdr) format.  MacOS X and Photoshop are
> smart enough to ignore the suffix and interpret the file correctly, though
> they may perform different tone-mapping operations to display them.  Hence,
> the differences you are seeing.
>
> There are no converters to JPEG or PNG image formats included with
> Radiance.  You can get to BMP, TIFF, GIF, Targa, Pict, PPM, and PostScript.
>  A typical conversion might go like this:
>
>        rpict [options] octree > result.hdr
>        ra_bmp -e auto result.hdr result_tm.bmp
>
> I have added "_tm" to the name to indicate that it has been tone-mapped.  A
> general tool for performing tone-mapping, which outputs to Radiance format
> but in a restricted range, is pcond.  A similar result to the above in PPM
> format may be obtained with:
>
>        pcond result.hdr | ra_ppm > result_tm.ppm
>
> Any other formats than those listed above will have to be reached using
> Photoshop, Photosphere, Preview, or other tools.  As I mentioned, they each
> have their own notion of tone-mapping, so your mileage may vary.
>
> As for the splotches and so forth, there are a plethora of options that
> affect rendering quality, and if there is nothing wrong with your model, the
> use of "rad" or "trad" is highly recommended to help you set up your
> simulation.
>
> Best,
> -Greg
>
> P.S.  As an interesting side-note, Unix tools do not even see the file
> suffix if you use redirection, i.e., "> output_file.sfx".  In the Unix
> tradition, none of the Radiance tools look at or enforce any particular file
> suffix usage, and everything is done by convention for the user's benefit.
>
> > From: Ji Zhang <hope.zh at gmail.com>
> > Date: April 26, 2011 6:57:11 AM PDT
> >
> > Dear Radiance experts,
> >
> > I'm testing rendering radiance scene using rpict with Radiance 4.0 in Mac
> OS 10.6.7
> >
> > Problem A:
> > I'm using the following rpict command:
> > rpict  -vf /test/view.vf -w  -aa 0.2 -ab 3 -ad 2048 -ar 128 -as 512 -x
> 500 -y 500 /test/scene.oct > /Users/oat/Desktop/image.jpg
> >
> > However, I have the following problem with the png file generated:
> > 1. the surfaces not facing the sun directly looks like being burnt
> > 2. there're a lot of black splotches along the edges and corners of the
> wall
> > 3. the image has a lot of jagged edges
> > 4. it cannot be open in photoshop but it can be previewed in Mac OS
> >
> > the preview of this png file as screen-captured is like:
> >
> https://2omvuw.bay.livefilestore.com/y1p8T69Ib9EOtRETgqUwtZrJ_hfoKx1uDj4hkHKIFICcIAZ17CFilr8bRaY0n6zURTGQpmdYWRALT2rnvmiz3cUmUDR8IG_-xBd/Mac%20OS%20png.png?psid=1
> >
> >
> > Problem B:
> > If I render the image as .hdr file it still have the same problem 1 to 3
> as mentioned above when I preview it in Mac OS. But the hdr image can be
> open in Photoshop and appears quite right with less severe splotch problem.
> >
> > The rpict command:
> > rpict  -vf /test/view.vf -w  -aa 0.2 -ab 3 -ad 2048 -ar 128 -as 512 -x
> 500 -y 500 /test/scene.oct > /Users/oat/Desktop/image.hdr
> >
> > The hdr image as opened in Photoshop is:
> >
> https://2omvuw.bay.livefilestore.com/y1p5J22wHNNnuKciUzj5slOchjNGAKcZ7NclFvCojDvwVmrgoglis8BQt4RB9BTaPLpbk3_3sjaJ11-TSpsM6ndEVuA5FKwZp3Y/Mac%20OS%20hdr.png?psid=1
> >
> >
> >
> > Problem C:
> > if I add a ground surface into the scene, the hdr image as rendered will
> have a lot of bright splotches along the bottom of the wall surfaces (the
> ground surface is positioned 0.3m lower than the floor surface of the room):
> >
> https://2omvuw.bay.livefilestore.com/y1perNd2uKYSrsH2hXoIZqyVynQkw1Eid2ULgDb-gY3VJ-Cb9ANIhZ1ZucPz7rZQynAypp_Fjskp1gN9pbgNneAp7A7Hbxzwa0B/Mac%20Os%20hdr%20_with_ground.png?psid=1
> >
> > The maximum dimension of the scene is around 100m after adding the ground
> surface.
> >
> >
> > I'd like to ask:
> > 1. why the png or jpg file generated using rpict in Mac OS can be
> previewed but cannot be open in Photoshop?
> > 2. why the png, jpg or hdr image generated using rpict in Mac OS looks
> "burnt out" when previewed?
> > 3. why only the hdr image file can be opened in Photoshop and appears
> normal?
> > 4. why does the additional ground surface cause the splotches? and how to
> correct it?
> > 5. how to get a clean hdr image with smooth surfaces that have no
> splotches and jagged edges?
> > 6. What are the key rpict parameters to control the image quality?
> >
> >
> > Can you kindly help to take a look and advise me the source of problem
> and the solutions?
> >
> > Thank you!
> >
> > Ji
>
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