Understanding texture mapping onto jit.gl.gridshape circle

Aug 13, 2006 at 5:22pm

Understanding texture mapping onto jit.gl.gridshape circle

Hi folks,

I’ve looked through the help files, tutorials, and even Andrew B.’s
great online Jitter articles and I’m having no luck figuring this out.

I’m trying to map a texture onto a jit.gl.gridshape circle, and it’s
being mapped differently than I want it to be mapped: instead of being
wrapped around the circumference of the circle, I’d like it to be mapped
from left to right, top to bottom (with the squared corners rounded off,
essentially). I guess this is a polar to cartesian transformation I’m
looking for, is that right? But I can’t figure out how or where to
apply that transformation.

I’m unsure if I’m even asking the question well enough, let me know if
not. But if anyone could give me some pointers, I’d greatly appreciate it.

Thanks!

Dave

#27141
Aug 13, 2006 at 5:53pm

The easiest thing to do is to create a circle mask for your texture’s
alpha channel and set @blend_enable 1 for the gridshape. That should
be straightforward enough since you don’t have to try and to the
poltocar thing. To create a circle mask in Jitter, use jit.expr like
this: jit.expr @expr “hypot(snorm[0], snorm[1])” and threshold it at
some value to create the maks.

best,
wes

On 8/13/06, Dave Della Costa wrote:
> Hi folks,
>
> I’ve looked through the help files, tutorials, and even Andrew B.’s
> great online Jitter articles and I’m having no luck figuring this out.
>
> I’m trying to map a texture onto a jit.gl.gridshape circle, and it’s
> being mapped differently than I want it to be mapped: instead of being
> wrapped around the circumference of the circle, I’d like it to be mapped
> from left to right, top to bottom (with the squared corners rounded off,
> essentially). I guess this is a polar to cartesian transformation I’m
> looking for, is that right? But I can’t figure out how or where to
> apply that transformation.
>
> I’m unsure if I’m even asking the question well enough, let me know if
> not. But if anyone could give me some pointers, I’d greatly appreciate it.
>
> Thanks!
>
> Dave
>

#81895
Aug 13, 2006 at 8:07pm

You can use the tex_map attribute to apply a texture to any GL Group
object using the object’s vertex coordinates. In this case the
incantation “tex_map 1, tex_plane_s 0.5 0 0 0.5, tex_plane_t 0 0.5 0
0.5″ should map a plane texture to the circle. Look at the HTML
reference to find out what all the tex_map modes do.

HTH,
Randy

On Aug 13, 2006, at 10:22 AM, Dave Della Costa wrote:

> Hi folks,
>
> I’ve looked through the help files, tutorials, and even Andrew B.’s
> great online Jitter articles and I’m having no luck figuring this out.
>
> I’m trying to map a texture onto a jit.gl.gridshape circle, and it’s
> being mapped differently than I want it to be mapped: instead of being
> wrapped around the circumference of the circle, I’d like it to be
> mapped
> from left to right, top to bottom (with the squared corners rounded
> off,
> essentially). I guess this is a polar to cartesian transformation I’m
> looking for, is that right? But I can’t figure out how or where to
> apply that transformation.
>
> I’m unsure if I’m even asking the question well enough, let me know if
> not. But if anyone could give me some pointers, I’d greatly
> appreciate it.
>
> Thanks!
>
> Dave
>

#81896
Aug 13, 2006 at 9:24pm

Nice! I always forget about those tex_plane_* attrs.

wes

On 8/13/06, Randy Jones wrote:
>
> You can use the tex_map attribute to apply a texture to any GL Group
> object using the object’s vertex coordinates. In this case the
> incantation “tex_map 1, tex_plane_s 0.5 0 0 0.5, tex_plane_t 0 0.5 0
> 0.5″ should map a plane texture to the circle. Look at the HTML
> reference to find out what all the tex_map modes do.
>
> HTH,
> Randy
>
> On Aug 13, 2006, at 10:22 AM, Dave Della Costa wrote:
>
> > Hi folks,
> >
> > I’ve looked through the help files, tutorials, and even Andrew B.’s
> > great online Jitter articles and I’m having no luck figuring this out.
> >
> > I’m trying to map a texture onto a jit.gl.gridshape circle, and it’s
> > being mapped differently than I want it to be mapped: instead of being
> > wrapped around the circumference of the circle, I’d like it to be
> > mapped
> > from left to right, top to bottom (with the squared corners rounded
> > off,
> > essentially). I guess this is a polar to cartesian transformation I’m
> > looking for, is that right? But I can’t figure out how or where to
> > apply that transformation.
> >
> > I’m unsure if I’m even asking the question well enough, let me know if
> > not. But if anyone could give me some pointers, I’d greatly
> > appreciate it.
> >
> > Thanks!
> >
> > Dave
> >
>
>

#81897
Aug 15, 2006 at 3:34am

Thank you Wesley and Randy–I ended up using Randy’s suggestion, and
this worked beautifully.

Much appreciated–

Dave D.

Wesley Smith wrote:
> Nice! I always forget about those tex_plane_* attrs.
>
> wes
>
> On 8/13/06, Randy Jones wrote:
>>
>> You can use the tex_map attribute to apply a texture to any GL Group
>> object using the object’s vertex coordinates. In this case the
>> incantation “tex_map 1, tex_plane_s 0.5 0 0 0.5, tex_plane_t 0 0.5 0
>> 0.5″ should map a plane texture to the circle. Look at the HTML
>> reference to find out what all the tex_map modes do.
>>
>> HTH,
>> Randy
>>
>> On Aug 13, 2006, at 10:22 AM, Dave Della Costa wrote:
>>
>> > Hi folks,
>> >
>> > I’ve looked through the help files, tutorials, and even Andrew B.’s
>> > great online Jitter articles and I’m having no luck figuring this out.
>> >
>> > I’m trying to map a texture onto a jit.gl.gridshape circle, and it’s
>> > being mapped differently than I want it to be mapped: instead of being
>> > wrapped around the circumference of the circle, I’d like it to be
>> > mapped
>> > from left to right, top to bottom (with the squared corners rounded
>> > off,
>> > essentially). I guess this is a polar to cartesian transformation I’m
>> > looking for, is that right? But I can’t figure out how or where to
>> > apply that transformation.
>> >
>> > I’m unsure if I’m even asking the question well enough, let me know if
>> > not. But if anyone could give me some pointers, I’d greatly
>> > appreciate it.
>> >
>> > Thanks!
>> >
>> > Dave
>> >
>>
>>

#81898

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