barycentric coordinates for quads

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barycentric coordinates for quads

Postby esmitt » Fri, 02 Jul 2010 07:50:18 GMT 

Hi everyone, some of you know how fill a quads in 2D using barycentric
coordinates?At the present, I'm splitting the quads into 2 triangles,
but that way is inefficient because I have to iterate over the second
bounding box which repeats pixel that were filled previously (by
example, to fill the 2nd triangle I traversed the 1st triangle that
belongs at bounding box formed by 2nd triangle)
Thanks

esmitt
Top

barycentric coordinates for quads

Postby esmitt » Fri, 02 Jul 2010 07:50:18 GMT 

Hi everyone, some of you know how fill a quads in 2D using barycentric
coordinates?At the present, I'm splitting the quads into 2 triangles,
but that way is inefficient because I have to iterate over the second
bounding box which repeats pixel that were filled previously (by
example, to fill the 2nd triangle I traversed the 1st triangle that
belongs at bounding box formed by 2nd triangle)
Thanks

esmitt
Top

Re: barycentric coordinates for quads

Postby Hans-Bernhard Brer » Fri, 02 Jul 2010 07:55:04 GMT 

Am 01.07.2010 00:50, schrieb esmitt:

I think we all know that that's a bad idea, so don't worry about its 
implementation too much.


You appear completely confused about the terms you're using.  What makes 
you think that filling using barycentric coordinates would require a 
bounding box?

And while we're at it: what makes you think barycentrics are a useful 
tool for a polygon into pixels?  They have nothing to do with pixels!
Top

Re: barycentric coordinates for quads

Postby esmitt » Fri, 02 Jul 2010 08:51:01 GMT 

Thanks for your answer.

On Jun 30, 6:55m, Hans-Bernhard Brer < XXXX@XXXXX.COM >


I know that a scanline solution better but for now, I need to use
barycentric coordinates.
Well, when I talk about bounding box is just like a delimiter for my
splitted triangle and iterate over each pixels and decides if (x,y) is
inside..nothing else

I'm using it to make another algorithms
Top

Re: barycentric coordinates for quads

Postby Hans-Bernhard Brer » Fri, 02 Jul 2010 22:24:25 GMT 

Am 01.07.2010 01:51, schrieb esmitt:



How did you arrive at the conclusion that you "need" them?  I have to 
ask again, because they make no sense whatsoever for the job at hand.


And what would be keeping you from iterating over the bounding box of 
the entire quad, and just evaluating

	if (pixel_inside_triangle1(x,y) || pixel_inside_triangle2(x,y))


Well, if you're going to loop over pixels in bounding boxes, that 
effectively _is_ a scanline algorithm anyway --- so what's keeping you 
from using a proper one?
Top

Similar Threads:

1.barycentric coordinates for quads 

Hi everyone, some of you know how fill a quads in 2D using barycentric
coordinates?At the present, I'm splitting the quads into 2 triangles,
but that way is inefficient because I have to iterate over the second
bounding box which repeats pixel that were filled previously (by
example, to fill the 2nd triangle I traversed the 1st triangle that
belongs at bounding box formed by 2nd triangle)
Thanks

esmitt

2.Barycentric coordinates in fragment shader 

Hi,

just curious if there's a neat way to get the barycentric coordinates
(or similar) of the current fragment in a GLSL shader?

Only way I could think of it was to render each triangle individually,
but that's not too good for performance...

- Asbjn

3.interpolation of barycentric coordinates 

Hello all,
I have points P1, P2 lying in a triangle A, B, C. I'm able to compute
barycentric coordinates of P1 and P2. Is it possible to interpolate
somehow the barycentric coordinates to obtain points which lie on the
line segment P1P2? Of course, I could interpolate linearly between P1
and P2, but I would like to interpolate bar. coordinates instead. Is
that possible?

Thanks.

Jindra

4.To turn barycentric coordinates to the world space 

Hi all,


I have a point in barycentric coordinates within a triangle, 
I know its vertex (in world coordinates).  


It is possible to turn the barycentric coordinates 
to the world space?


Thanks in advance !!

5.Barycentric Coordinates on a Cuboid ? 

Hi there,

    Assume one point is within a cuboid,
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of the coboid.
    Could someone tell me how to calculate the weight for those vertices?
    or any reference paper?

    I only know the same case within a convex polygon and a tetrahedron..
    subdivide the cuboid into several tetrahedra?

    Thanks very much : )

Best Regards,
Brian

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