Normal Tag: What's that?


#1

I get these normal tags on meshes imported from other programs. They don’t have any attributes, couldn’t find anything about them in the help documents and I don’t see any difference in the objects if I delete them. So, what are they for?


#2

c4d automatically generates normal directions based on the poly and its neighbours, with a phong threshold to make sharp edges. Other apps handle phong and edge breaks in different ways, the phong tag contains this.

Theres no easy way to see, edit or change these, so either leave the tag on if it looks fine or delete it if youd like c4d to handle the phong shading.


#3

Thank you. Maybe that’s why I see some weird phong effects when I optimize imported meshes. I’ll check this.


#4

Works with R11.5 Windows 32 Bit. 64 not testet.
http://skinprops.com/addnormals.php


#5

Actually, you can use these normals to your advantage, Jorge.
Sometime ago, I needed a piece of geometry that should be perfectly flat but still react to light and reflection is if it had volume.
So, I exported the model in COLLADA and opened it again. It came with those Normal Tags attached (of course, the model is completely polygonal). Then I deleted all the back polygons (you can do it, in case you don’t need them) and then I flattened the geometry (some geometry can be completely flattened, other can be almost flattened).
You end up with a flat model that has the information of the direction of the normals. Even the Index of Refraction can be used for this flattened geometry. Of course, in this case (transparency) the geometry can not be completely flattened otherwise polygon overlapping would occur.
Check out this video for a simple demo:

http://ruimac.com/movies/normal_tag_01.mov

Rui Batista


#6

Amazing Rui!


#7

Yes awesome !
I usually just delete them.
Pe


#8

normal tags are also very usefull in importing other files like from nurbs based software.
in rhino.io you get the exact nurbs curvature data in the normal tags, so the polygons render exact as the original nurbs surface would in rhino itself.

if you want to change the geometry, it is in most cases wise to delete the normnal tag, as it is intented to use on the original imported geometry(excluding ruis great trick).

if the imported files come in with normal tags it is often best to leave them as they are, they are most likely already very good to render.

cheers
stefan
rhino.io


#9

Additionally depending on how the imported NURBS generated object looks and is layed out poly wise it will also render in a very ugly style if you delete the normal tags. Rounded surfaces with filleted round cutouts done in rhino will most likely not render nicely if you delete the normal tags on the meshes.

Knowing that you have to keep in mind that normal tags are also a bit bitchy. Rotating the axis (pivot) of an object will destroy the normal tag. So will mirroring objects for example.


#10

Thanks for the link Hardkorn, had missed your post.


#11

Thank you all for your info. Very valuable.


#12

Normal tags are essential to keep intact. The reason being is they represent a more accurate smoothing than just a simple phong tag smoothing. When dealing with NURBS geometry you have the ability to control creases and such, which isn’t easily handled by C4D (unless you do HyperNURBS weighting) and features like this is accounted for when using the normals that are exported/imported through CAD translators.

The same can be said of systems that utilize vertex normals for smoothing and colouring so if you are in a pipeline sharing these assets do not delete the normal tag.


#13

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