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Re: Question about edges
March 10, 2013 07:31PM
Hi Roland,

Yep - exactly what I expected with 6085: - a rounder-than-real life shading. :-)

I think you may find per pixel lighting makes the lighting effect _worse_...particularly if you use per pixel lighting for what it's really good for: shininess. (The problem with per-vertex lighting is that the fall-off from specular hilights is very steep, so the hilight tends to be contained entirely within one triangle. Once you have that 'sharp' hilight, the induced roundness will make lighting that really looks...well...round.) I hadn't noticed the error on the slope bricks because they look nice for the roundness of the lighting.

I just coded a smoothing algorithm (which, having not run it yet, I must assume works perfectly :-), but it takes the opposite approach: it uses only lines, rather than only angle, to do smoothing/creasing. I'll post some pics once I have it integrated, which may not be for a few days.

Having gone through the coding exercise, I think I can state a 'wish list' of assumptions about the library for a smoothing algorithm:

1. The bit-wise locations of all colocated vertices match exactly - that is, no floating point jitters between vertices that should touch.
2. All faces that form a smooth edge share the (bitwise) same coordinate values and the (bitwise) same transform stack. (In other words, if you want two sub-parts to mesh smoothly, they must be transformed in the same way.)
3. All parts are BFC valid. (Because of this, two adjacent faces will have edges going in opposite directions along the triangle.)
4. Any lines used to indicate a crease have a start and end point that (bitwise) matches the location of the corners of the triangle edge that they crease. (The line does not have to go in any particular direction, as it will always match one of the two triangle faces.)

This wish list allows apps that smooth meshes to avoid any epsilon math checks, computational geometry tests, etc. Smoothing behavior is (theoretically) predictable:
- every exactly manifold edge that doesn't have a manifold line is smooth.
- every exactly manifold edge that has a manifold line is creased.
- non-manifold edges are crease (or rather, aren't eligible for smoothing because they aren't even considered to be connected).

Cheers
Ben
SubjectAuthorViewsPosted
Question about edges Roland Melkert530March 08, 2013 12:41PM
Re: Question about edges Philippe Hurbain234March 08, 2013 11:07PM
Re: Question about edges Roland Melkert239March 09, 2013 11:11AM
Re: Question about edges Philippe Hurbain224March 09, 2013 11:25AM
Re: Question about edges Roland Melkert243March 09, 2013 12:23PM
Re: Question about edges Ben Supnik230March 09, 2013 08:18PM
Re: Question about edges Philippe Hurbain233March 09, 2013 10:53PM
Re: Question about edges Roland Melkert279March 10, 2013 11:35AM
Re: Question about edges Philippe Hurbain253March 10, 2013 12:00PM
Re: Question about edges Ben Supnik247March 10, 2013 04:11PM
Re: Question about edges Roland Melkert261March 10, 2013 04:32PM
Re: Question about edges Ben Supnik255March 10, 2013 07:31PM
Re: Question about edges Travis Cobbs240March 10, 2013 10:19PM
Re: Question about edges Ben Supnik231March 10, 2013 11:20PM
Re: Question about edges Tim Gould298March 10, 2013 11:40PM
Re: Question about edges Ben Supnik237March 11, 2013 11:52AM
Re: Question about edges Roland Melkert229March 11, 2013 01:31PM
Re: Question about edges Tim Gould242March 11, 2013 01:58PM
Re: Question about edges Roland Melkert234March 11, 2013 04:48PM
Re: Question about edges Tim Gould253March 11, 2013 04:57PM
Re: Question about edges Roland Melkert216March 11, 2013 06:02PM
Re: Question about edges Tim Gould231March 11, 2013 06:24PM
Re: Question about edges Travis Cobbs245March 11, 2013 10:12PM
Re: Question about edges Tim Gould253March 11, 2013 02:07PM
Re: Question about edges Ben Supnik277March 22, 2013 03:33PM
Re: Question about edges Tim Gould268March 22, 2013 03:44PM
Re: Question about edges Ben Supnik276March 22, 2013 04:48PM
Re: Question about edges Philippe Hurbain317March 23, 2013 01:49AM
Re: Question about edges Travis Cobbs225March 11, 2013 11:20AM
Re: Question about edges Roland Melkert246March 11, 2013 01:50PM
Re: Question about edges Roland Melkert210March 12, 2013 11:15AM
Re: Question about edges Ben Supnik227March 12, 2013 11:24AM
Re: Question about edges Roland Melkert214March 12, 2013 11:37AM
Re: Question about edges Travis Cobbs214March 09, 2013 10:57PM



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