# [Bf-committers] Re: A little Editface Question

Ton Roosendaal ton at blender.org
Thu Jun 9 12:46:40 CEST 2005

```Hi,

I would sugest a new method. The set_wuv() is a horrible construction
at the moment. Afaik, Johnny already solved copying pinning flags, seam
flags, smooth flags, and so on.

What is needed now is a parametric solution for finding new UVs and
vertexcolors based on an existing face and a 3d coordinate that lies
within the plane of that face. That's basically just an interpolation
function.

Code below was copied from render module, I didn't compile it! But it
has the ingredients :)

/* input efa and co (vector */
/* output in TFace: uv (2 values) and vcol (4 char values) */
void set_uv_vcol(EditFace *efa, float *co, float *uv, char *col)
{

/* define best projection of face XY, XZ or YZ */
xn= fabs(efa->n[0]);
yn= fabs(efa->n[1]);
zn= fabs(efa->n[2]);
if(zn>=xn && zn>=yn) {i= 0; j= 1;}
else if(yn>=xn && yn>=zn) {i= 0; j= 2;}
else {i= 1; j= 2;}

/* calculate u and v */
v1= efa->v1;
v2= efa->v2;
v3= efa->v3;

t00= v3->co[i]-v1->co[i]; t01= v3->co[j]-v1->co[j];
t10= v3->co[i]-v2->co[i]; t11= v3->co[j]-v2->co[j];

detsh= 1.0/(t00*t11-t10*t01);	/* potential danger */
t00*= detsh; t01*=detsh;
t10*=detsh; t11*=detsh;

u= (co[i]-v3->co[i])*t11-(co[j]-v3->co[j])*t10;
v= (co[j]-v3->co[j])*t00-(co[i]-v3->co[i])*t01;

/* btw; u and v range from -1 to 0 */

/* interpolate */
l= 1.0+u+v;

/* pseudocode!!! */
/* just fill in colors or UV texture values here */

new = l*vertex3_val - u*vertex1_val - v*vertex2_val;

}

OK... this now doesn't work yet, since we need to get it working for
Quads.

That's a simple case as well;

/* in other triangle */
if(efa->v4 && l < 0.0) {
/* do it all over, but now with vertex 2 replaced with 4 */

}

So, would this work?

-Ton-

On 9 Jun, 2005, at 3:22, Martin Poirier wrote:

> Then, all of the new face will have a different
> percent value on the cut edge. It's on the original
> edge anyway, so pretty easy to figure. 1.0/number of
> cutes * conversion factor to store in short.
>
> Martin
>
> --- Johnny Matthews <johnny.matthews at gmail.com> wrote:
>
>> the problem is that there will be 1 or more cuts per
>> face (the code
>> allows for unlimited cuts per edge)
>>
>> I'll look at the code you mentioned and see if it
>> can point me in the
>> right direction though.
>>
>> On 6/8/05, Martin Poirier <theeth at yahoo.com> wrote:
>>>
>>>
>>> --- Johnny Matthews <johnny.matthews at gmail.com>
>> wrote:
>>>
>>>> Ok, This is for any self-professed Mesh Gurus
>> out
>>>> there,
>>>>
>>>> I am getting very close to having a working
>> version
>>>> of the edge-based
>>>> subdivide with the option of 1 or more even
>> cuts.
>>>> The
>>>> hitch I have is this. I have a function that
>> takes
>>>> each new internal
>>>> face as it is created and copies information
>> from
>>>> the parent
>>>> face kinda like facecopy(EditFace
>> source,EditFace
>>>> target), where target
>>>> is always a subface of source. Can you think of
>> a
>>>> way, without passing any more information to the
>>>> function to extrapolate
>>>> the UV and Vertcol information from the source
>> face
>>>> to the target face.
>>>
>>> This one's for me.
>>>
>>> You'll want to call the function: set_wuv in
>>> editmesh_tools.c
>>> First argument is the number of verts (could
>> easily be
>>> removed).
>>> Second argument is the new face, then the vertex
>> flags
>>> (explained in the nice ascii drawing in the
>> fonction's
>>> body) and then the pinned face (original face
>>> containing pinned uvs flags and the like).
>>>
>>> To use the function correctly, you have to call it
>>> with the proper vertex flags AND also set the f1
>> flag
>>> for each edge that is being cut. This sets the
>> factor
>>> of where the cut is along the edge starting from
>> the
>>> first vertex in the edge (0.0) to the last (1.0)
>>> stored in a short (multiplied by 32768).
>>>
>>> If you have more questions, you can contact me
>>> directly.
>>>
>>> Martin
>>>
>>>
>>>
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>>
>> --
>> Johnny Matthews
>> johnny.matthews at gmail.com
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------------------------------------------------------------------------
--
Ton Roosendaal  Blender Foundation ton at blender.org
http://www.blender.org

```

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