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View Full Version : Send in the clones! (PointClone+ problem)


PanzerBoy
09-27-2004, 03:17 PM
Okay, so I'm trying to make an outdoor scene. To simulate plants and grass growing along the shore of a lake I need to clone a large number of simple 2-poly objects with transparency maps applied to them. I thought I could simply use pointclone+ but it doesn't seem to work correctly once I've imported the cloned objects into layout.

Basically, if I clone a bunch of these 2-poly objects (called grass_Simple)

http://oak.ucc.nau.edu/del/3DGallery/cgtalk/t1/simplegrass.jpg

over a bunch of points that looks sorta like this:

http://oak.ucc.nau.edu/del/3DGallery/cgtalk/t1/points.jpg

the result is a jumbled mess in my scene like this:

http://oak.ucc.nau.edu/del/3DGallery/cgtalk/t1/pointclone.jpg

(I've moved the cloned plants up so it's easier to see the problem)

What's happening (I think) is that the surface that fit so nicely onto the 2-poly grass_Simple object no longer "fits" after I've cloned the polys a few hundred times over the points. If I manually position a few individual instances of grass_Simple objects in Layout it works as expected. Unfortunately, cloning and positioning hundreds of these things manually would get tedious real fast.

So what to do? I'm guessing that I need to be doing the cloning from within layout but I'm not sure how. Any suggestions guys?

dies-irae
09-27-2004, 03:33 PM
The map is sized to the simple object bounding box, when you clone it in modeler, the bounding box becomes adapted the whole object instead of every single instance of the object.
To correct it, put a uvmap on the single object, apply the transparency map using the uv, and then clone as you wish.

kangonto
09-27-2004, 06:48 PM
By the way, have you tried with clip maps instead of transparency maps?, It renders a lot faster.

jabbermike
09-27-2004, 06:58 PM
if you canīt use UV for some reason, the old school way was:
clone the original another time by the same amount of points without offsetting (use the normal clone tool), then make a BGmorph with the clones that were created by point clone +
then use the morph in layout.

mike

faulknermano
09-27-2004, 07:54 PM
try these cloners:

layout: http://thespread.ghostoutpost.com/FamilyCloneGN.zip
modeler: http://www.flay.com/GetDetail.cfm?ID=1319 (pointclonextra4)

SplineGod
09-27-2004, 08:37 PM
Create your crossed poly object in modeler. Use point clone plus to scatter and clone the object. Go to Map----texture-----poly map-----New Quad Polygon Map.
This will allow you to place a texture on every quad polygon at the same time.

I also agree about using clip maps vs transparency maps.
Another trick that works is that you can use the points that you set up for doing a point clone and apply HV sprites to those. Your grass image can be mapped onto the sprites.

jabbermike
09-28-2004, 06:17 AM
I also agree about using clip maps vs transparency maps.
It seems to me that clipmaps often donīt antialias as nice as transparency maps.

mike

SplineGod
09-28-2004, 06:38 AM
You dont want to antialias clip maps in the texture editor because it causes funky problems.
The way around the jaggies is to use fairly high rez image maps. They can be used at a lower rez color depth since it only sees black and white.

jabbermike
09-28-2004, 09:51 AM
oh, youīre so right! that never dawned on me! I would have saved a lot of rendering time.:shrug:

mike

PanzerBoy
09-28-2004, 04:04 PM
Hey, thanks for all the great suggestions, guys! I'm at my non-CG day-job right now, otherwise I'd post an updated render.

Anyway, I went the UV route as dies-irae suggested and that did the trick. And the render times weren't too adversly affected. This isn't for an animation so it's okay if it takes a couple minutes to render. But I'm going to try the clip-map and HV sprite methods, though.

However, I did encounter another strange problem. In the places where there were a lot of cloned plants bunched together (like in the valley between the two hills in my original render) I'd get a white "snow"-like affect. It was almost like the transparent polys were acting like prisms and bouncing white light from the horizon back at the camera. I fiddled with reflection/refraction surface options to no avail. Eventually I discovered that if I boosted the ray recursion limit (Render option) from the default of 16 to the max of 24 it would help but not completely do away with the "snow" artifacts.

So, the only way I found to get rid of the "snow" was to reduce the number of clones in the affected areas. I'm guessing this limited the number of transparent polys the rays were bouncing through so the raytracer was able to more accurately determine the correct color. Deleting clones worked but left those areas looking a little sparse. As a workaround I'm going to try making my crossed-poly plant objects larger and with more blades of grass per clone so I can use fewer of them.

Would clip-maps work better than transparancy maps to limit the "snow" rendering artifacts?

PanzerBoy
09-29-2004, 03:38 AM
Here's an updated WIP render showing what I have so far:

http://oak.ucc.nau.edu/del/3DGallery/cgtalk/t1/r02.jpg

The crossed-poly grass is still very regular and needs a lot more work. But I guess I'm pretty happy with how this scene is progressing. Render times were about 2 minutes before I added the hypervoxel bushes. Now I have to turn off the hv bushes or else it's 15+ minutes on my P4/2.8GHz PC. Sheesh!

SplineGod
09-29-2004, 03:47 AM
I would use a combination of things.
That far away you would get away with simple grass done with simple geometry. You could at least do some reeds or cattails using simple polygonal objects.
You can also use just flat polys instead of crossed polys. Just put some image maps on the flat polys that look like grass. At the distance youre at I dont think youll notice the difference.
You might also take a look at using Saslite for some grass too.
I would also take a look at using clip maps on simple flat polys that are colored to look like grass using procedurals. Bushes can be done using baked hypervoxels. :)

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