# 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

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

> 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

>

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

>

Nice! I always forget about those tex_plane_* attrs.

wes

On 8/13/06, Randy Jones

>

> 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

> >

>

>

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

>>

>> 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

>> >

>>

>>