[x3d-public] Nurbs patch coloring

[Don Brutzman]

On 1/27/2018 4:27 AM, Michail Vidiassov wrote:
> [...] PS. Really I look for a way to reproduce old good gluNurbs results.

Thanks very much for this line of inquiry Michail, it is not a common technique in X3D but it will be great to understand these important general capabilities better.

gluNurbs references:

	OpenGL Programming Guide, Chapter 12, Evaluators and NURBS
	http://www.glprogramming.com/red/chapter12.html

	CSE 457 Introduction to Computer Graphics, Autumn Quarter 2008, OpenGL Examples
	https://courses.cs.washington.edu/courses/cse457/08au/tools/opengl-examples.html

If you are able to share some specific 3D examples of what you think is appropriate (such as gluNurbs demos), please do so.  They will help us better consider what can currently work, and what might get improved.  Am expecting that improvements in both the baseline X3D specification and also in authoring/export tools will be needed... we shall see.

FYI related recent work produced 2 test scenes that display coverage and correctness for a variety of polygonal nodes.  They are useful to provide a snapshot of a browser's support.  Links:

	Visual verification scenes for image texture mapping: new test models
	compare support for multiple geometry nodes by multiple #X3D players.
	Encourages consistent content rendering for authors, helped improve #Xj3D player.
	https://twitter.com/Web3DConsortium/status/945009048625094657

	Visual verification scenes for texture mapping, updates to Xj3D and X3D-Edit
	http://web3d.org/pipermail/x3d-public_web3d.org/2017-December/008034.html

	X3D Example Archives: X3D for Advanced Modeling, Texture Mapping, Texture Map Comparisons Cylinder
	http://x3dgraphics.com/examples/X3dForAdvancedModeling/TextureMapping/TextureMapComparisonsCylinderIndex.html

	X3D Example Archives: X3D for Advanced Modeling, Texture Mapping, Texture Map Comparisons Rectangle
	http://x3dgraphics.com/examples/X3dForAdvancedModeling/TextureMapping/TextureMapComparisonsRectangleIndex.html

It would be a good thing to start a corresponding X3D test scene that shows expected NURBS coloring and texture support.  Since texture mapping assigns pixel colors to shape locations, and since parametric NURBS geometry defines scalable shapes rather than explicit polygon vertices, texture mapping seems like the right direction to pursue for coloring NURBS patches.

For X3D version 4, we are already working on multiple texture improvements to Projective Texture Mapping (PTM) and also RenderedTexture (environment mapping) variants.  So any NURBS texturing progress will be in good company and welcome.  Comprehensive improvements will later be likely to occur across multiple browser implementations, if the X3D specification can define (and example scenes can demonstrate) all of these texture-related capabilities appropriately.

Again thanks for considering important questions, looking forward to continued insight.  Good luck with your work.

all the best, Don
-- 
Don Brutzman  Naval Postgraduate School, Code USW/Br       brutzman at nps.edu
Watkins 270,  MOVES Institute, Monterey CA 93943-5000 USA   +1.831.656.2149
X3D graphics, virtual worlds, navy robotics http://faculty.nps.edu/brutzman