# Normals / Material Node >> Material

I `m surching for a usefull appliance of the normal button in the node material >> input >> material I can see how to use it, but I don`t know when.

Any suggestions?

 see below

 see below

Ok here you go.

All the above is wrong (I think)

Searching for normal node:
http://mediawiki.blender.org/index.php/Talk:Manual/Material_Nodes

http://mediawiki.blender.org/index.php/Reference/Windows/Nodes/Material_Nodes#Normal

http://mediawiki.blender.org/index.php/Release_Notes/Notes242/NodeCompositor

http://mediawiki.blender.org/index.php/Template:Manual/Normal_Node

And finally from the release notes:
http://www.blender.org/cms/Blender_Composite_Node.744.0.html

Ok updated the above. These all seem to refer to a “dot product” whatever that is. Product being the mathematical result of a multiplication task and dot being a decimal point?

Toni Grappa: the Normal input on a material node gives you control over the normal vectors, so you can override the mesh geometry. For example, if you set a Geometry node to View and connect its output to this socket, the lighting flattens out as if the light is coming from the camera. So it seems to be useful as a first step to a “relighting” tool. The Normal node itself that Marty_D refers to seems to be more useful though, because you can adjust the orientation of the sphere interactively.

Marty_D: Dot product is from vector calculus and is used to calculate the light intensity at a given pixel by comparing the vectors representing the face normal and the direction of a light source. It is a way to get a scalar value (intensity) from vectors. In the simplest case if these vectors are at right angles, the dot product is zero (cos 90 = 0) and the pixel is dark. If they are parallel, all the light is reflected back toward the light source (cos(0) = 1). The final rendering of a pixel takes into account all kinds of other considerations like the angle relative to the camera, the surface’s reflectivity etc.

I dug all this up from residual memories of high school calculus. I could see how you would use the theory for cool edge-lighting or fresnel like effects, but I still don’t understand actually how to use the Dot output of the node.

Thanks for the answers. The generel informations about Normals I allready read and we had a nice discussion about vectors, Skalar Products and all that mathematic stuff concerning normals on blendpolis (the german blenderforum). So it can be a “relighting” tool - ok . I´m writing an article for german Blenderwiki and I´m allways interested in practical examples, how one can use this function, the “killer application”. I have never seen a nodesetup which used the normal entrance on material node., but I haven`t seen much yet

Ok thanks CD38. I can see how I’ll never use that.
Toni. Sorry for walking all over your thread. Thanks for the direction. Picked up a new feature today.

Toni: Did anyone at blendopolis actually understand what the Dot output of a normal node is doing? ie what vectors are actualy being multiplied to get this scalar? Thank you.

Yes, Solentgreen knows the answer. He gave a realy nice mathematical explanation . I cannot translate his answer into english, but here is the link
http://blendpolis.serverpool.org/f/viewtopic.php?t=12036

My own explantion works without mathematics.
One vektor “is looking” out of the camera and he “sees” many other vectors of the object. With the vectors at the border of the objekt the “Cameravektor” has an angular of 90 degrees.
He “sees” one vektor just right in top view, so they are parallel. 90 degrees (COS)= 0, 0 degrees (COS) = 1. The rest ist inbetween.

i think, (and no, I did not write it,) that the Material Nodes’ Normal and Vector examples are the best. I am trying to stretch my brain to apply them to compositing…

Example, how to calculate the Dot Value

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Danke für den Link und das Bildchen

Well, I did not know it was that easy. My courses on Linear Algebra and Calculus were not a waste of time, after all…and that node really seems to be quite powerful.