[Radiance-general] rpict image rendering problem

[Greg Ward]

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