Re: ambient lightsource

["guillaume laforge" <guillaume.laforge.3d(at)gmail.com>]

I pingo,

There is already a distance shader in the render tree. Here is how to use it : http://www.vol2nuit.fr/guillaume/blog/distance_shader/distance_shader.html

Cheers

Guillaume

On Dec 1, 2007 10:43 AM, pingo van der brinkloev <pingo(at)pingofilm.dk> wrote:

Bernard you nailed it. It's very useful!

Matt, I think you're right that it has to be done to the shader. That would probably also be quite clever, since then maybe one could do it with all kinds of stuff (nulls, meshes, curves?).

also sounds right to me about the incandescence.

U have some good suggestions about writing a shader, if only I could do that life would be a bit easier for me.

So a scalar node for the shadertree that measures  light intensity or even distance from a point.

MAN could i use that!!!!!!!

(this is normally the time when someone quietly notifies me that it's present in the blablabla folder and it's called the MI distance shader TADAAA)

I am trying to wrap my brain about this, but to be honest I think it's straight up nuts that the feature isn't just there.

I'm SO tired of using days to figure out how to do simple stuff in XSI. Simple stuff that is a click of a button in other apps.

And now I have to be a shader writer and learn c+ and python etc, etc. It's all fun, but also VERY time consuming.

c ya

pingo

but how to write one???

On 01/12/2007, at 03.55, Matt Lind wrote:

My only point was that in order to get shading on a surface that ignores normals, it has to be done in whatever shader is attached to the surface port of the object's material.  A light cannot make that kind of modification on it's own.  A light shader only computes how much illumination reaches a surface.  It's the material shader's job to apply the illumination to the surface.
 
As for incandescence, it's just a color value added to the surface's color (I think) after illumination has been computed.  It does not consider normals.  Similar to global ambience, but uniformly applied to the object's surface.
 
To recreate the effect as I understand it being described to me, you would have to write a shader that looks at a specified object in the scene (a light in this case) and modulates the incandescence intensity based on proximity from the shading point to the light.  If you don't want to write a shader (or don't know how), you could write a self-installed custom operator to modulate the intensity of colors in a vertex color map because vertex colors can be read in the rendertree using the standard Vertex RGBA shader, then fed into whatever phenomena you have setup on the object.  Either plugged into the incandescence of a material shader like Phong, or composited with some math nodes in the rendertree (such as a mix8color).
 
I'm sure if you rack your brain enough other solutions will come to the fro.
 
Matt


------------------------------
Matt Lind
Animator / Technical Director
SOFTIMAGE certified instructor:
SOFTIMAGE|3D
SOFTIMAGE|XSI
Matt.Lind(at)Mantom(dot)net
 
 

Date :  Fri, 30 Nov 2007 20:51:39 -0500

To : XSI(at)Softimage.COM

From  : "Bernard Lebel" <3dbernard(at)gmail.com>

Subject : Re: ambient lightsource

The advantage of the max way (and probably the C4D one as well) is
that since it's being controlled by a light, it affects surfaces using
the light's radius.
Imagine using a point light as a spherical volume that increase the
incandescence within its radius. That's incredibly useful to give a
slight illumination boost to an overly dark area without modifying the
overall light setup.
And btw I'm not exactly sure the effect is the same as incandescence.


Bernard

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