Re: Overide on material

[Andy Jones <andy(at)thefront.com>]

Problems to be aware of with texture maps (though they sound like they 
may solve your problem):

1) In my experience, XSI will crash, or objects will render black (or 
maybe something else might happen) if you have a shader access a texture 
map property on an object that has a texture_map but no uv set applied.

2) You can't, as far as I know, use elliptical filtering.  Maybe you can 
use the mip-mapping-like filtering, but I haven't tried it.

3) You can't put texture_maps on clusters in any productive way that 
I've found, so you're more or less stuck with one texture.

4) This isn't technically a problem, but in an ideal world, texture maps 
would look like little miniature shader fragments instead of being 
monolithic image look-ups.  This would, for one thing, solve the 
filtering problem.  It would, however, probably mean that shader 
texture_maps would have to become something different than the 
texture_maps people use to drive mappable parameters.

The other common solution is to use vertex colors to drive a switching 
mechanism (see Nathan's thread and the color_interpolate node) you'd set 
up in the render tree.  Also, see Bernard's article on XSI-Blog 
http://www.xsi-blog.com/?p=75.  Of the two methods (texture_maps and 
vertex colors), vertex colors seem to be a lot more common and tested, 
despite being the less natural solution to the problem.  It's a much 
more general tool, too, because you can do things with a range of values 
that you can't do with a discreet switch.  The biggest advantage of the 
texture_map, as I see it, is that it should require less data overhead, 
and it doesn't really complicate your shader graphs as much.  And you 
can add objects and textures with to the system without ever changing 
the shader.

-Andy

Chris Marshall wrote:

> Thanks Nathan, will take a look!
>
>
> Turner, Nathan wrote:
>
> > Found it..
> >
> >
> >
> > So this is similar to the thread I had earlier... (One shader, many
> > clusters (trying to reference Texture maps from clusters)
> >
> >
> >
> > Fortunately for you, this will probably work out.
> >
> >
> >
> > Make your objects and put your material on them all as a shared
> > material.
> >
> >
> >
> > Click one object ,go to Get > Property > Texture_map > Texture map and
> > apply a Texture_map node to each object independently, and pick the map
> > you want on each.  You can get back to this by going to the explorer
> > view and opening up your object  Then in your shader place a
> > Color_lookup node to the channel you need, Diffuse, ambient, whatever.
> >
> >
> >
> > In Render tree    NODES > Map Lookups > Color (c)  
> >
> >
> > If you just do this with the default names the lookup node will grab the
> > first Texture_Map node on the objects.  Check your explorer to see what
> > the Texture_map node looks like.
> >
> >
> >
> > Hope this helps.
> >
> >
> >
> > Note:
> >
> >
> > Seems Texture_map nodes are part way to completion and just need the
> > extra push to be seen if they are on a cluster.
> >
> > Nathan Turner
> >
> >
> >
> > ________________________________
> >
> > From: owner-xsi(at)Softimage.COM [mailto:owner-xsi(at)Softimage.COM] On Behalf
> > Of Chris Marshall
> > Sent: Thursday, May 25, 2006 8:15 AM
> > To: XSI(at)Softimage.COM
> > Subject: Re: Overide on material
> >
> >
> >
> > But why does it do this? Is it a bug, feature, what?
> >
> > kim aldis wrote:
> > Partitions. It'll still  lock the material while you're in that pass but
> > at
> > least it'll work.
> >
> > Partitions are sort of groups, so you could try groups, I guess. One for
> > each object then override on the group.
> >  
> >
> >     -----Original Message-----
> >     From: owner-xsi(at)Softimage.COM 
> >     [mailto:owner-xsi(at)Softimage.COM] On Behalf Of Chris Marshall
> >     Sent: 25-May-2006 12:25
> >     To: xsi(at)Softimage.COM
> >     Subject: Overide on material
> >          Hi All,
> >     I have about 12 objects all with the same material on. Each 
> >     one is going to have a different image textured on.
> >     So what I want to do is have 1 material then add an overide 
> >     to each object and specify the different images. But when I 
> >     do this, XSI creates a new material by itself, which says 
> >     <locked by overide> which doesn't reference back to the 
> >     original base material. Huh?!
> >          Is there a way of doing this?
> >          Thanks
> >          Chris
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