Micropoly displacement...?

Discuss stuff not about Indigo.
User avatar
CoolColJ
Posts: 1738
Joined: Mon Jun 25, 2007 1:47 pm

Micropoly displacement...?

Post by CoolColJ » Fri Sep 21, 2007 8:17 pm

MPD is good, but vector displacement mapping is even better 8)
you can displace in multiple vectors rather than just outwards

ie displace a mushroom from a flat plane :)

BbB
Posts: 1996
Joined: Fri Feb 09, 2007 8:28 am
Location: Berlin
Contact:

Post by BbB » Fri Sep 21, 2007 8:44 pm

Yep. One of the features the new Modo has...

User avatar
Kram1032
Posts: 6649
Joined: Tue Jan 23, 2007 3:55 am
Location: Austria near Vienna

Post by Kram1032 » Sat Sep 22, 2007 4:38 am

- traditional difference map - you take TWO meshes. one mesh is hires sculpt, the other mesh is low poly cage that will be displaced at render time. the difference between HIRES and LORES is encoded into the LOW RES MESH'S UV MAP TEXTURE. only ONE uv map is taken into consideration.

- vector displacement map - you take TWO meshes. one mesh is hires sculpt, the other mesh is low poly cage that will be displaced at render time. the difference between HIRES and LORES is encoded in the LOW RES MESH"S UV MAP TEXTURE. BUT... when that comparison between hires and lores is made, BOTH the hires mesh's uvs and the lores mesh's uvs are taken into account and a CORRESPONDENCE is made between the uvs.

this allows the computer to say "ah, this vertex on the lores mesh CORRESPONDS to that vertex on the hires mesh". in traditional difference mapping, THEY DON'T CARE about correspondence, just the distance from hires to the NEAREST POINT on the lores.

since a correspondence is made, a determination can be made in regards not only how far away a point is from the nearest point on the other mesh, but we can say that the corresponding vertex went up 2 and left 3 and forward 7.

THIS allows you to encode undercuts like mushrooms.
_____
hum...
wouldn't that mean, you need a hires and a lores mesh?
or how does it work, with directly using a texture?
(MPD is clear, but VDM?)
_____
Edit: ah!
I found a pic of such a map :D I think, now I have a slight idea, how it works :)

http://www.xsibase.com/forum/index.php? ... 34;start=0

BbB
Posts: 1996
Joined: Fri Feb 09, 2007 8:28 am
Location: Berlin
Contact:

Post by BbB » Sat Sep 22, 2007 5:25 am

VDM works with coloured maps, a bit like normal maps but with a broader spectrum. Somehow (and really I haven't got much of a clue) the colours and their intensity correspond to movements not just along the normals (as in the case of a 16 bits black and white displacement map), but also laterally along the two other axes. That's the gist of it as far as I understand it.

User avatar
zsouthboy
Posts: 1395
Joined: Fri Oct 13, 2006 5:12 am

Post by zsouthboy » Sat Sep 22, 2007 5:37 am

Yeah VDM is complicated compared to mpd.

I've never seen an implementation of VPD, either - I'm gonna have to look at this Modo business that people have been raving about :D

User avatar
Kram1032
Posts: 6649
Joined: Tue Jan 23, 2007 3:55 am
Location: Austria near Vienna

Post by Kram1032 » Sat Sep 22, 2007 5:51 am

yeah, I saw it, already!
HDR-normalmaps, where black means no displacement^^
there, .exr might come in useful :D

must be really hard to add...

IanC
Posts: 147
Joined: Thu Aug 24, 2006 4:46 am

Post by IanC » Sat Sep 22, 2007 10:55 am

That must be a bitch to work out the ray intersections!

User avatar
Kram1032
Posts: 6649
Joined: Tue Jan 23, 2007 3:55 am
Location: Austria near Vienna

Post by Kram1032 » Sat Sep 22, 2007 10:30 pm

for now, MPD is enough, but if you manage to add VDM, that would be amazing :D

- although, how do you get maps for that?

I guess, with some node-setup, you *could* get something like that in blender, but it will be quite complicated...

BbB
Posts: 1996
Joined: Fri Feb 09, 2007 8:28 am
Location: Berlin
Contact:

Post by BbB » Sat Sep 22, 2007 11:13 pm

I guess you really need a VDM sculpt tool like Modo's that can handle .exr or .hdr maps. One problem is memory though. Even a 1k .exr map is pretty heavy to handle...

Benr
Posts: 2
Joined: Fri Nov 10, 2006 1:53 am

Post by Benr » Wed Sep 26, 2007 10:25 am

I wrote the XSI vector displacement plugin that Kram1032 referred to:

http://www.xsibase.com/forum/index.php? ... 34;start=0

It works exactly as he described. You bring both the low and high poly versions of an object into XSI from your sculpting program. Then XSI's Rendermap property walks the UV space to generate a difference map. The maps can get huge, e.g. hundreds of MB for 32 bits/channel and 2K or 4K size.

I also had to write a simple shader to expose Mental Ray's vector displacement capability.

Where vector displacement gets a little more complicated is if you use tangent space. Exactly as with normal mapping, if you want to be able to deform your low poly object after generating your displacement map, then you need to use tangent space. Unfortunately, there is no standardization of how tangent space is derived among different applications (and there are several possibilities). If you want to generate the displacement map in one app and render it in another, you have to be careful that the tangent space methods match up.

BbB
Posts: 1996
Joined: Fri Feb 09, 2007 8:28 am
Location: Berlin
Contact:

Post by BbB » Wed Sep 26, 2007 11:02 am

Thanks for the explanation Ben.

User avatar
psor
1st Place Winner
Posts: 1295
Joined: Sun Jun 25, 2006 1:25 am
Location: Berlin
Contact:

Post by psor » Wed Sep 26, 2007 12:34 pm

Thanx Ben, I appreciate that you droped in here! ;o))


take care
psor
"The sleeper must awaken"

User avatar
Kram1032
Posts: 6649
Joined: Tue Jan 23, 2007 3:55 am
Location: Austria near Vienna

Post by Kram1032 » Thu Sep 27, 2007 1:52 am

thanks :D

User avatar
CTZn
Posts: 7240
Joined: Thu Nov 16, 2006 4:34 pm
Location: Paris, France

Re: Micropoly displacement...?

Post by CTZn » Thu Mar 12, 2015 2:48 am

CoolColJ wrote:MPD is good, but vector displacement mapping is even better 8)
you can displace in multiple vectors rather than just outwards

ie displace a mushroom from a flat plane :)
<3
obsolete asset

User avatar
thesquirell
Posts: 428
Joined: Fri Aug 29, 2014 3:49 am
Location: Novi Sad, Serbia

Re: Micropoly displacement...?

Post by thesquirell » Thu Mar 12, 2015 7:06 am

I would love to see this in Indigo, as well.

Post Reply
17 posts

Who is online

Users browsing this forum: No registered users and 33 guests