Hugo wrote:
> 
> Hello!
> 
> I'm really glad whenever I see people want to improve POV, and are able
> to do it!  ;o)  Now, pardon me for being dumb maybe but I still wonder
> why you are not using a simpler method for blurring.
> 
> I can imagine my idea isn't working with transparent surfaces, but.. In
> my opinion it wouldn't produce a wrong result if: POV renders the
> reflection in the "ordinary" old way, but into a separate buffer instead
> of the screen. Then use simple and fast gaussian blur, and them UV map
> it onto the object again, as a pigment.
> 
> I don't know if nearby objects are supposed to blur less, according to
> physics, but if so, then we could use the same method as post-processing
> camera depth blur.
> 

Your idea has strong similarities with megapov's post-processed focal blur and
has the same pros and cons (like being strongly resolution dependant).  As you
said near objects should have less blur than those far away, so you would use
the depth information like with focal blur. Right now post processing neither
supports transparency nor reflection, so things would not work correctly in many
cases.  Furthermore results with semitransparent objects would be very bad
anyway.

Your mapping idea does not seem that good to me, because it would only lead to
interferences and the need for interpolation or high resolution and therefore
slower rendering times.  

> I know there's a tricky thing according to edges of the object, if it's
> blurred my way. But my idea is that the buffer should contain a
> reflection of the object that "follows the objects shape".
> 

The edges are handled quite well with focal blur, so that would not be the
problem.  There are quite a lot of problems with post processed blur like the
enormous memory use when working with large images and the things mentioned
above, so it probably could not replace other methods.  Anyway it could be a
nice addition to the depth post processing (which is used by focal blur IIRC) to
support transparency and reflection, although i don't think it's that easy to
implement.

Christoph

-- 
Christoph Hormann <chr### [at] gmxde>
Homepage: http://www.schunter.etc.tu-bs.de/~chris/

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In article <39E### [at] mailmedk>, Hugo <hug### [at] mailmedk> 
wrote:

> I'm really glad whenever I see people want to improve POV, and are able
> to do it!  ;o)  Now, pardon me for being dumb maybe but I still wonder
> why you are not using a simpler method for blurring.
> 
> I can imagine my idea isn't working with transparent surfaces, but.. In
> my opinion it wouldn't produce a wrong result if: POV renders the
> reflection in the "ordinary" old way, but into a separate buffer instead
> of the screen. Then use simple and fast gaussian blur, and them UV map
> it onto the object again, as a pigment.

This sounds like "environment mapping", rendering an image from the 
position of the object and using that for reflection/transparency 
information. The disadvantages of this are a big loss in the accuracy of 
the reflections, the finite resolution of the environment map, memory 
use, time spent generating the maps, etc...blurred reflections and 
transparency are easy to fake when using environment mapping, but adding 
this to POV would not be so easy. And to get even slightly accurate blur 
effects, you would have to store depth information too...and reflections 
of objects close to or on the surface would look really bad.
The advantage to this method is speed, and it can be used easily in 
scan-line renderers(most scan-line renderers use this method, and some 
can resort to the ray-tracing method POV uses now for higher quality 
reflections).

Or are you talking about some kind of post process, marking the area of 
the image and saving the necessary data for later processing? How would 
this handle reflections of reflecting objects, etc? Also, it would still 
not be as accurate, and wouldn't exactly be easier to implement.
My patch can blur anything that uses the Trace() function, which could 
make it useful for a couple other things I have in mind besides 
reflection and transparence...your idea sounds like it would require 
special handling for this.


> I don't know if nearby objects are supposed to blur less, according to
> physics, but if so, then we could use the same method as post-processing
> camera depth blur.

If you think about it, they would have to blur less...
Get a piece of some kind of blurry transparent plastic(or sandpaper a 
piece of clear plastic). Get a book and press the plastic against a 
page, and slowly pull the it away.
And the camera blur post_process isn't totally accurate either, it has 
problems with transparent and reflecting objects. These problems aren't 
bugs, but a result of the shortcuts taken to allow it to be done later 
as a blur filter. The original kind is more accurate(and uses a method 
similar to my patch, shooting a bunch of sample rays).

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

<><

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We could try intersection, or blob...but those might look rather gross. :p

ian

Ron Parker wrote in message ...
>But then you wouldn't be able to see parts of Nathan, because you'd get a
>coincident surface problem with the two copies of him.

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