Someone please teach me how the diffraction works

[Pibuz]

Hi guys!

I know this might be a quite well-known topic, but I really cannot understand how the diffraction and obstacle maps work (working with Sketchup, it must be said: I think that a small buggie is lurking here but I'm no expert so I'm not sure...)!

I got from the manual that diffraction produces those wonderful blooms, and that their dimension gets bigger when the f/stop number is higher: ok, got it. That's all good as far as I use apertures.

But, question number 1: I can't see any differences if I choose an obstacle map too.. Is that alright?

question 2: can an obstacle map be used even without activating the diffraction?

question 3: HOW THE HECK I CONTROL IF THE AD IS PRE OR POST PROCESSED? I read that the post-processed kind is very heavy, drains loads of RAM and it's quite slow to see in the GUI. I think I am usually running this one, I suppose, since I report the exact same conditions. But how can I set and control the pre-processed one?


Thank you a lot...
Be patient......

EDIT: now that I'm just testing it, I see that the image autosaving doesn't save the diffraction: I have to manually save the image to get it.. One more question mark for me

[tar_gniK]

As far as I know, the pre/post diffraction option must be edited in the .igs file.

[Oscar J]

I can choose between physical and post-pro AD directly in Blendigo. Guess they just haven't integrated it into Skindigo yet.

[Pibuz]

...I remember that A VERY LOOONG TIME AGO there was a wonderful postproduction utility made for Indigo.
You could adjust, change and modify the diffraction, along with many more postpro parameters such as chromatic aberration, sharpening, color adjusting.....

I REALLY MISS THAT!!!!!!!!!
I REALLY REALLY THINK THAT INDIGO COULD AND SHOULD TAKE ALONG SUCH AN INTEGRATED TOOL!

..it would really be a dream..

[Oscar J]

There has been such features? Are you sure you're not thinking about Luxrender?

[tar_gniK]

I think you're referring to Violet, or something like that? Either way, something like that should come back, and a standalone material editor, imo.

[Pibuz]

There has been such features? Are you sure you're not thinking about Luxrender?

My dear Oscar.... I've known and loved Indigo since a very long time ago......

[fenerolina]

Good post Pibuz! I didn't find a way to make fine flares too. Will play with that too, so how's your test scene setup?
That's what we should achieve righ?
http://tolas.wordpress.com/2008/08/21/glare/

Yes, It was Violet

[Pibuz]

Yes exactly.

..in all of those test there is diffraction+obstacle.

Would be cool to have a series of tests conducted with and without obstacle, just to see what are the differencies.

I worked a little last evening, but my test scene was quite lame. Would be cool if we shared the same scene so we can split the work in two

I use sketchup btw, I don't know if that's a problem...

[fenerolina]

Yes good idea!
No problem, I'm a sketchup user too.
Running on 3.6.26 and sketchup 8

[Pibuz]

Ok then!

I have a slightly wider collection of maps for glare and obstacle at home, I'll share those with you this evening.

Then, we should organize a simple grid to indicate the combination of the maps and the resulting coded render, so that we know that map a + map b = render 1, or map a and no map b = render 2

I can prepare the scheme.

You could work a little on a simple-yet-fancy scene for the tests if you want!

[yonosoy]

Hi all. From this part a chart serie of parameters related in aperture diffraction will be in trunk.
The serie is for traced and post-produced difraction (even modalities of process). As Zom-B's advised, for this purpose some mirrored spheres and the sun could be a good "dummie", since there are aperture from direct light (sun) and refrlected light.
Those are good intentions... if there are any kind of communal work around, this machines could help a little.

P.D: beggining to prepare a dummie scene in this way.

Thanks for this proposal.

[Pibuz]

Ok guys, I attach my small collection of maps.
That's all for today: long and difficult day..

See you tomorrow!

[fenerolina]

The ones from Tolas seem to work well, didn't try the others yet. Thank you.
Don't know how the scene should be to make nice and fast tests. Interior or large space? (does it matter?) Big light sources with small ones? Is it necesary to put some reflective elements in the scene as yonosoy suggested? As you can see I need a croquis
Yonosoy, I'm looking forward to see your dummie scene.

[Pibuz]

I think that a fancy scene would be something kinda like:
- a cubic rooom 4x4x4m,
- a thin tall cylinder on the left coming down from the ceiling with a punctual emitter on the bottom
- a metallic teapot on the floor, on the right
- a square flat emitter over the teapot (there's a cool SU plugin for that, don't remember the author..)

From this we should get almost all the conditions to see the glares!

tell me what you think