Re: bump mapping with procedural textures?

[Francois Lord <francoislord(at)gmail.com>]

Yes. The Bumbmap Generator adds the projection to the state and passes 
it on to its children nodes. They recieve it, pass it to their children 
and so on until it reaches the Vector State node. The Vector State takes 
the projection from the state, puts it in the coord input of its parent, 
and then each node start to calculate their stuff and pass the result to 
their parent.

The state is some kind of table containing various data about the 
object, polygon, normal, UV, distance, etc. The material node gives the 
state to its children in a particular order, and each node can read and 
write to this state. This makes it possible for a node to modify the 
state before another one reads it. This is exactly what the Bumpmap 
Generator does: it recieve the state first, modifies the normals, and 
give it back to the material node. Then it is given to the Phong node, 
which only reads the state and shades the object according to the new 
normals.

I'm not a shader writer. I took all this from a seminar given by Dave 
Lajoie. I thought it was good stuff to know, even for ordinary users to 
understand the render tree better.


André Adam wrote:
> Since I have first seen that setup I try to get my head around the 
> Texture Vector the Vector State node returns. That one should be 
> dependend on the Texture Projection, no? If the object carries 
> multiple UV Spaces, how does the Vector State node decide which one to 
> use? Does it forward-traverse the Render Tree branch it is connected 
> to until it finds a shader having a Texture Space reference (in this 
> case the Bumpmap Generator)?
>
>
> brad wrote:
>
> > Here are the steps that illustrate the problem:
> >
> > 1- Assign a lambert to a primitive nurbs sphere
> > 2- Connect the bumpmap generator to the bumpmap material input
> > 3- In the bumpmap generator, create a planar XY texture projection
> > 4- Connect the procedural fractal texture to the bumpmap generator input
> > 5- Connect the Texture Space Edit node to the fractal coordinate 
> > input, set the UV remap max to 10,10,10
> > 6- Connect the Vector state node to the texture edit input, set the 
> > state to Texture Vector
> > 7- Render region the sphere.
> > 8- :-)
> >
> > 9- Go to the bumpmap generator and create a spatial texture projection
> > 10- Render region the sphere. 11- :-(
> >
> > 12- Get a projection lookup node and pipe it into the texture edit 
> > coordinate input
> > 13- Pipe the texture stream into the surface input of the material
> > 14- Render region the sphere
> > 15- :-/
> >
> > Bumpmaps work fine for planar, spherical, and cylindrical 
> > projections, but not for spatial. Please explain.
> >
> >
> >  
> >
> > > > -----Original Message-----
> > > > From: owner-xsi(at)Softimage.COM
> > > > [mailto:owner-xsi(at)Softimage.COM] On Behalf Of brad
> > > > Sent: 23-March-2006 21:35
> > > > To: XSI(at)Softimage.COM
> > > > Subject: RE: bump mapping with procedural textures?
> > > >
> > > > The issue we've been running into with procedural bumpmaps
> > > > has to do with topologies more complex than spheres or tori,
> > > > such as landscape with multiple caves and holes (our prior
> > > > show!). In such situations we tend to use procedural textures
> > > > since they can be easily applied in a seamless fashion via a
> > > > 3D spatial coordinate system.
> > > >
> > > > Unfortunately, while RGB results are fine for where the
> > > > surface intersects the spatial texture coordinates, it
> > > > doesn't work for bump map vector space. You need to create a
> > > > 2D texture map for bumps to work.
> > >
> > > I'm not sure I follow you.
> > >
> > >
> > >
> > >
> > > >
> > > > Thus the question, does the Zbump node work for procedural
> > > > textures using spatial coordinates?
> > > >
> > >
> > > I've been getting very good results.
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