Why not Screen mapping reflections?

[Lupaz]

Hi,

I´ve read some threads here that advice to use sherical or cylindrical mapping for Vray reflection slot. But those distort the reflection map so much that, in the case of a cloudy sky, no clouds are reflected at all.
Instead, using screen, clouds are reflected just fine.

I´m just wondering, so...

Thanks.

[Trapezium]

I don't ever use screen but I thought that the problem was just the case with diffuse (GI Skylight) and not specular reflections.

You can try using the tile and offset, in combination with spherical for your sky and you may get the desired effect. I would test it by just rendering with some reflective primitives.

--Jon

[mike.edel]

the distortion is just a matter of having the right texture format/layout

for spherical you need an unwrapped spherical panorama

example:
http://www.telfs.cc/specials/PeteruPaul-gross.jpg
http://www.telfs.cc/specials/Telfs-Zentrum-gross.jpg

this wraps into a sphere and gives distortion-free reflections

screen wont give you correct reflections on the sides/back of your object

spherical maps are more difficult to produce, but they give better top/bottom reflection than cylindrical ones
you might want to google for panorama creation/stitching (there are free tools to do this)

cya,

Mike

[Lupaz]

Jon: yeah, that did the trick. Stupid me never tried with offset

Mike: I couldn´t find a free creation software yet. All freeware are viewers only. Which one is it that you use?


Thanks.

[Trapezium]

Cool, just to add to that workaround. If you're not compositing in post, you may want to make two versions of the map.

Make one tilable for the reflection override slot using the info in this thread

http://www.chaoticdimension.com/foru...ic.php?t=11420

and for the visible environment you can use the screen mapped version but you'll have to make sure to override the GI environment also with either a flat color or the spherical mapped version or even a spherical mapped gradient ramp for a different form of control on the lighting.

--Jon

[mike.edel]

Panorama Tools:
there are different versions around, the original autor got problems with some patents and had to stop the development, others continued a bit,

original (without the patented parts)
http://webuser.fh-furtwangen.de/%7Edersch/

other version
http://www.path.unimelb.edu.au/~dersch/

ps: try a search for: pano tools

other than that, photoshop cs has a working tool

richard rosenman's spheremap plugin for photoshop/compatible does some corrections to the textures used in spherical procjection (removes pinches at top/bottom):
http://www.richardrosenman.com/software/spheremap.zip

there are others, but those are the ones i have used

mike

[Lupaz]

Thank you guys!