Hi guys,

Not exactly a specific MoI question - but I figure someone on here might be able to help...

As an artist, I'm looking at exploring primitive shapes and colour gradients, a little like this guy: http://www.markfell.com/wiki/

I was looking at doing the basic modeling in MoI, then throwing the ONurbs into Rhino for some Grasshopper action - but turns out to bake your colour gradient functions you have to mesh your objects, and I'd like to keep the objects with that smooth nurbs shader look. Plus I'd like to output image to large format - not sure how I'd do this within Rhino.

I was thinking maybe Processing, or Jitter, but again you have to mesh.

Does anyone have any ideas as to how I could achieve that beautiful smooth look on my geometries, have some control over the colour, and export at a high quality?

Thanks!

- Rich

Hi Rich, you can get a good smooth NURBS-looking result from a meshed result if you get vertex normals used to shade the polygon mesh.

The most common way to get that is to use OBJ format for the export out from MoI, when MoI exports to OBJ format the vertex normals included at the corners of every polygon come from the original NURBS surface and they're used for the shading and that greatly helps the polygons to look the same as the original NURBS model, they really make a big difference.

So getting vertex normals coming through would be the main thing to look for.

- Michael

Hi Micheal,

Thanks but correct me if I'm wrong but if I wanted to apply a colour gradient to this surface, because it's a mesh the gradient wont be smooth (because the surface has been is 'pixelated' as it were by the creation of n-gons?)

It's difficult for me because I don't know the technical terminology - apologies.

I guess what I would be looking for would be a way to apply custom shaders to surfaces...

- Rich

Hi Rich,

here's an (old) example from a modo Artist (sorry don't remember her name) were she used gradients on a polygon mesh (28.000 quads) as you can see the surface is smooth. The only thing, if i'm not mistaken, is you have to watch out for the export settings in MoI (density of polygons) if you really want to print really high resolution images, to see not a "facetted" look. You may have to create also a UV map in your 3D app to apply for example color gradients from images to your surface. Or as you mentioned use shaders in your 3D app, which provide color gradient creation functions.



Regards
Stefan

Its Laura Lediaev ;)
http://www.modsimviz.com/
All of the images displayed were rendered (ray-traced) with either Luxology Modo or Maxwell Render. C++ programs were written to create/process the meshes for the geometry, and scripts for importing the scenes into Modo.

Sweet - I'm going to give it a try with as many quads as I can handle!

- Rich

Hi Rich,

> Thanks but correct me if I'm wrong but if I wanted to apply a
> colour gradient to this surface, because it's a mesh the gradient
> wont be smooth (because the surface has been is 'pixelated' as
> it were by the creation of n-gons?)

There isn't really anything special about NURBS compared to polygons when it comes to regular shaders being applied, you should be able to apply a color gradient shader to a polygon mesh object in the same way that you would have applied to to NURBS output, and in fact most likely anything you'd be doing with NURBS would actually be converting it into polygons when it did the actual rendering.

I guess it could depend on the specifics of the shader that you're using though. But if it's a procedural shader that just works off of 3d point positions though that would work fine with polygons.

- Michael

Hmmm - the amount of quads I'm having to make is making everything super sluggish, and I'm still getting lines in the render (vray) - arg!

Question: in the viewport window (native to MoI) - the way the geometry is rendered out, you get a smooth transition between highlights and shadow - how does this work exactly?

- Rich

Why does the object have to be a mesh for a gradient to be applied? Confused!

- Rich

1280x960 - if this was blown up, definite quad-mare (and the file is 64 meg)...Damn those quads :)

Hi Rich,

> Question: in the viewport window (native to MoI) - the way the
> geometry is rendered out, you get a smooth transition between
> highlights and shadow - how does this work exactly?

That uses a technique called Gouraud shading:
http://en.wikipedia.org/wiki/Gouraud_shading

Under regular Gouraud shading colors are calculated at each polygon vertex and then when the polygon is drawn an interpolation is used that blends between the colors at the vertices.

Are you possibly doing your shading only with each individual polygon being a separate color? If so then that's the problem - you want to instead use some kind of interpolation mechanism like Gouraud shading or some kind of procedural shader so that color is calculated at a much finer level like per indiviudal output pixel rather than only one color for a whole single polygon.

- Michael

Hi Rich,

> Why does the object have to be a mesh for a gradient to be applied? Confused!

Sorry I don't quite understand what you are referring to here - you're talking about some other software here and not MoI in particular, is that correct?

- Michael

Yes sorry I was Michael - Rhino via Grasshopper. In that case, it appears that each polygon has a different colour within the mesh. I think Gouraud was what I was getting at, the gradient has to be interpolated to give a smooth look...I don't quite know how to approach this predicament! Does anyone know of any softwares that will allow me to play around with such shading using open nurbs objects (pipe dream)?

This is all very interesting thank you!

- Rich

Hi Rich, look for things like "false color" or "vertex colors" something like this:
http://geometrygym.blogspot.com/2011/09/mesh-false-color.html

You want something that will let you specify colors per _vertex_ rather than a per _face_ color value.

Most mechanisms that allow you to supply color information at the per-vertex level will also handle interpolating the colors along the interior of the polygons that connect the vertices.

- Michael