View Full Version : triple...........

 xiao_x10 October 2004, 05:02 AMWhat use for triper polygon???izzit after triple the polygon will render faster???But after triple the polygon will be increase 2x I use the qemLoss2 for reduce polygon,but after reduce that become triple polygon......,any polygon reduce will maintain to the 4 point polygon?? After triper polygon will render more acurate?Increase radiosity render time???As i know radiosity calculate by veryex point,not polygon........ Y after i triple the polygon look bad if i subpatch it.........
SplineGod
10 October 2004, 07:20 AM
tripling is also useful for making sure you dont have nonplanar polys which can sometimes cause render errors. :)

NanoGator
10 October 2004, 07:42 AM
In addition to what SplineGod said, also be aware that you only use Triple in certain situations. By default, quads are really the way to go. That is what Lightwave likes best.

The reason why Qemloss triples the polygons is because a triangle cannot (except for one very rare circumstance) be non-planar. It is a lot easier to do perform the geometric computations to reduce the polygons when they are all triangles. Your model would look a little better if you fixed some of the tripling caused by Qemloss, but you wouldn't see much of a change in render times, if at all.

Rei Ayanami
10 October 2004, 09:09 PM
Nanogater : what situation would that be, i cant think of it.

10 October 2004, 09:47 PM
I'll venture a guess since it piqued my curoisity, i guess to be planer it has to have a plane parallel to the polygon, so the degenerate situations were the three points a collinear, or in exactly the same place don't form polygons at all so they can't be planar.

NanoGator
10 October 2004, 09:59 PM
Padmus got it. Put the 3 points in a straight line and you get a non planar tri. Wish I could remember who it was that pointed that out to me.

uncon
10 October 2004, 10:02 PM
videocards like triangles.

The way that lightwave renders, doubling the amount of polygons to be rendered does not double the render time.

Larrikin
10 October 2004, 11:02 PM
A straight line isn't a triangle or polygon I agree, but it's always planar.

chikega
10 October 2004, 12:13 AM
mmmm? well, actually a line is straight, but straight doesn't mean planar. To have a plane, is to describe a surface - a line has no surface...

man, this is really getting metaphysical ... and if a tree fell in the woods, would it make a sound? :)

particle
10 October 2004, 01:00 AM
videocards like triangles.

The way that lightwave renders, doubling the amount of polygons to be rendered does not double the render time.
To go off of what uncon said, most polygon based render engines turn all the polygons into triagnles during the render process. The reason for this is the ray-triangle intersection routines are fast (n-gon routines are not). The ability to have more than 3 points on a polygon is just a neat modelling interface technique, but deep down inside they are really triangles.

Ryan

Serif
10 October 2004, 08:24 PM
A plane can be defined by three points that are non-linear. Three linear points is simply a line.

Larrikin
10 October 2004, 01:46 AM
Hey if anyone has a diagram of a non-planar straight line I'd love to see it.
Xiao_x there is a Qemloss3 (http://amber.rc.arizona.edu/lw/qemloss3.html#Installation) it's supposed to give better results. It would be great if there was a plugin that would reduce the polycount in an efficient way but keep quads. Don't think it exists though.

Serif
10 October 2004, 02:15 AM
IMHO, the semantics are being criss-crossed. Three points in a line should be described as co-linear and not planar. Planar basically means "having a flat surface" and a line has no surface. It is one dimensional. A planar polygon has two dimensions.

Three colinear points do not describe two dimensional space and therefore can not be planar.

:)

I win.

gerardo
10 October 2004, 02:16 AM
I use the qemLoss2 for reduce polygon,but after reduce that become triple polygon......,any polygon reduce will maintain to the 4 point polygon??

After using QuemLOSS (btw, already goes for version 3) you can test using MergeTrigons (http://www.dproject.com/lw_plus_e.htm), I usually use this plug-ins mixture when I use metaballs, then I activate subpatch; gives good results :)

Gerardo

NanoGator
10 October 2004, 02:19 AM
A straight line isn't a triangle or polygon I agree, but it's always planar.

Not if you draw it like this:

(1)-----(3)-----(2)

You have a 360 degree angle there.

*edit: I meant to say 180 instead of 360. Stupid me.

Serif
10 October 2004, 02:27 AM
how do three co-linear points describe an angle? regardless of selection order? :)

well, if i were to cave to quantum madness, i would say there was a 180 degree angle... not 360... but i guess that depends upon whether you're measuring the inside or outside... um... quantum anti-matter angles.

NanoGator
10 October 2004, 02:35 AM
Hehee.

Actually, you're right, it is 180. I actually posted that first, then edited it to 360, but then thought about it again and grrrrrrrrrrrrrrrr.

Here's how 3 colinear points become a 180 degree angle. (again, apologies for saying 360 in my previous post.)

Say you're watching somebody from a top-down perspective. They're walking East from point 1 to point 2. When the stop at point 2, they have to turn in order to walk towards point 3. They have to turn 180 degrees to go back the opposite way.

The reason I use that metaphor is that you have to think about what the smoothing algorithm has to do in order to smooth the angle of two polygons. In this case, the not only does the surface change to hard-to-rationalize degree, but also, the polygon has a surface area of 0. You cannot have a plane with an area of 0, in 3 dimensional space.

Serif
10 October 2004, 02:43 AM
...
Say you're watching somebody from a top-down perspective. They're walking East from point 1 to point 2. When the stop at point 2, they have to turn in order to walk towards point 3. They have to turn 180 degrees to go back the opposite way.

Therein lies the problem. Three co-linear points do not describe 2D space. Your friend would never be able to turn around. :)

Rei Ayanami
10 October 2004, 10:48 PM
Seirf : but your friend wouldnt have a concept of turning around and just go backwards instead (thats not real physics)

OK thankyou everyone for all explaining what this isnt (if you get me).

Once 1 angle on the triangle reaches 180, the other 2 have to be 0, which would make it only have 1 angle, and thefore its not a triangle.

Joviex
10 October 2004, 12:37 AM
There is no spoon.

:D

xiao_x
11 November 2004, 01:26 AM
Thanks for the comment from everyone......

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