some displacement questions/suggestions

[samuel_bubat]

Hi there,

I´m testing vray´s displacement mapping at the moment
and first of all.. it´s superior !!!

There are some thing´s I have noticed.
I want to make some mountains with vray displacement
so far it works well... but i get some artefacts if i increase
the displacement amount

take a look at these two pictures




ok it seems logical to me that these artefacts appear because a bitmap
only has 255 color tones... so it´s probably a kind of posterisation that appears.

I can use the blur filter in the bitmap rollout to decrease these artefacts...
but i loose details and i get (as stronger the blur is) other kinds of artefacts...

see the pictures below





so i thought... let´s do something clever :=)
convert your picture to a hdr
so i loaded 10 instances of the same image into hdrshop
and assembled a hdr image.
and surprise... suddenly my "mountains" are much higher by default
(displace amount 1) than with a low dynamic range picture
but the artefacts are still presents... (I even used the hdrshop
build in blur filter to interpolate between color tones)
but no change

I get the same result when i use a ldr with amount of 10 compared with a hdr and an amount of 1 ...
hmmm well due to a displacement map works perfect with 3d maps
like cellular there must be a way to create an hdr from a heightfield
that uses the complete range of 96bit to avoid these arefacts.

Any ideas how to assemble a hdr heightfield like mentioned ?

Maybe there is allready a solution.. or hidden switch i didn´t find ?

Another idea would be.. to write a HDR heightfield generator... =)
(sorry I´m not a programmer and have no idea how to do so)

Yet another idea would be to write a bitmaploader for max
that just blurs the y axis. (z axis in max) (Don´t ask me how)

I would so much like to generate realistic mountains with bitmap/hdr
based displacement mapping

(actually the same problem appears with max standard displacement
mapping and very high poly counts)

another question.. wht does the "quality" settings in the displace rollout
do... i never saw any change if i increased or decreased the settings
just the rendertimes change ?

the heightfield generator i used is called world machine and you can
download it here
http://students.washington.edu/sschmitt/world/
it offers the best erosion features i have seen so far
give it a try !!!

cheers

sam

[flipside]

Couldn't this be a problem of the resolution of your map?

Try this:
http://www.chaoticdimension.com/foru...ht=summed+area

and

http://www.chaoticdimension.com/foru...t=displacement

[samuel_bubat]

Thank´s for reply....
well.. hmm the threads you posted.. just show that other users also have the same problem =)

Vlado mentioned to set the subdivision size to the size of the image...
this doesn´t work... the artefacts just got stronger as higer the displacement resolution is...

but i found a way to increase the quality...

I wrote that i allready used hdrshop to generate a HDR...
I tried it once again using Digital Fusion
and it works
What I did was... building a flow
added a "change depth" (set to floating point)
added a colour corrector (changed gain to 10)
added a very little bit of blur....
and saved the file as HDR

these pictures show the results
(no bitmap blur filter was changed)
but as you can see... hdr is better.. but not perfect...
maybe 96bit is just not enough

Low Dynamic range



High Dynamic Range

[stefan]

Just a wild guess: Have you played with the accuracy value of the displacement modifier?

Stefan

[cocolas]

that's interesting- I never thought using hdri for displacement - I suppose you wouldn't need Digital Fusion to make that either.....athough it helps.

is there a diference in render time when using HDR vesus LDR?