POV-Ray : Newsgroups : povray.binaries.images : Object Labels Server Time: 29 Sep 2020 23:53:33 GMT
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From: Melody
Subject: Object Labels
Date: 19 Jan 2020 03:50:00
Message: <web.5e23d1b255a34c109da690110@news.povray.org>
/*
right=up.eye
eye=right.up
up=eye.right
*/
#declare campos = <0,80,-250>;
#declare cameye = vnormalize(<20,12,0>-campos);
#declare camup = <0,1,0>;
#declare camright = vnormalize(vcross(camup,cameye));
#declare camup = vnormalize(vcross(cameye,camright));
#declare FontSize = _clamp(1.7,0.1,2);
#declare camang = 40;

camera {
  location campos
  right camright
  up camup *(image_height/image_width)
  direction cameye*(image_height/image_width)
  angle camang
}

#macro label(Text,objv,r,col)
#local vl = vlength(objv-campos)/88;
#local pnt = camup*((r*.95)+vl*FontSize)+objv;
#local eye = vnormalize(pnt-campos);
object {
  text {
    ttf "Arial.ttf" Text 2 0
    texture {  pigment { rgb col }  finish { ambient 1 diffuse 0 } }
  }
  translate x*(strlen(Text)*-0.28)
  scale <vl*FontSize,vl*FontSize,vl*FontSize>

popmatrix(vnormalize(vcross(camup,eye)),vnormalize(vcross(eye,vcross(camup,eye))),eye,pnt)
  no_shadow
}
#end
label("HELLO 162",<60,24,80>,48,<0.0196, 0.0196, 0.2156>)
label("Here are 492",y* 29.9,24*.8,<0.30196, 0.0196, 0.2156>)

so u can likely tweak to get the result


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From: Melody
Subject: Re: Object Labels
Date: 19 Jan 2020 04:25:01
Message: <web.5e23d89428c763ef9da690110@news.povray.org>
reminder, popmatrix() is Matrix_Trans(A, B, C, D) in POV.
transforms.inc
translations are easier when u stick to same name funcs.
limited RAM upstairs.


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From: Melody
Subject: Re: Object Labels
Date: 19 Jan 2020 04:50:00
Message: <web.5e23df6528c763ef9da690110@news.povray.org>
oh right, now I remember. for bottom text, consider font height.

#macro label(Text,objv,r,col,top)
#local vl = vlength(objv-campos)/88;
#if (top)
#local pnt = camup*(r*1.05)+objv;
#else
#local pnt = -camup*(vl*FontSize+r)+objv;
#end
#local eye = vnormalize(pnt-campos);
object {
  text {
    ttf "Arial.ttf" Text 2 0
    texture {  pigment { rgb col }  finish { ambient 1 diffuse 0 } }
  }
  translate x*(strlen(Text)*-0.25)
  scale <vl*FontSize,vl*FontSize,vl*FontSize>

popmatrix(vnormalize(vcross(camup,eye)),vnormalize(vcross(eye,vcross(camup,eye))),eye,pnt)
  no_shadow
}
#end


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From: Melody
Subject: Re: Object Labels
Date: 19 Jan 2020 05:05:01
Message: <web.5e23e2ca28c763ef9da690110@news.povray.org>
and finally, start with
#declare camup = <-1,1,0>;

text is transformed, and its normal points at camera.


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From: Melody
Subject: Re: Object Labels
Date: 19 Jan 2020 06:20:00
Message: <web.5e23f45928c763ef9da690110@news.povray.org>
remove redundant,
add scale to text centering. done.

/*
right=up.eye
eye=right.up
up=eye.right
*/
#declare campos = <0,80,-250>;
#declare cameye = vnormalize(<20,12,0>-campos);
#declare camup = <-1,1,0>;
#declare camright = vnormalize(vcross(camup,cameye));
#declare camup = vnormalize(vcross(cameye,camright));
#declare FontSize = _clamp(1.7,0.1,2);
#declare camang = 40;

camera {
  location campos
  right camright
  up camup *(image_height/image_width)
  direction cameye*(image_height/image_width)
  angle camang
}
#include "transforms.inc"
#macro label(Text,objv,r,col,top)
#local vl = vlength(objv-campos)/88;
#if (top)
#local pnt = camup*(r*1.05)+objv;
#else
#local pnt = -camup*(vl*FontSize+r)+objv;
#end
#local eye = vnormalize(pnt-campos);
object {
  text {
    ttf "Arial.ttf" Text 2 0
    texture {  pigment { rgb col }  finish { ambient 1 diffuse 0 } }
  }
  translate x*(strlen(Text)*-0.15*FontSize)
  scale vl*FontSize
  Matrix_Trans(vnormalize(vcross(camup,eye)),camup,eye,pnt)
  no_shadow
}
#end
label("HELLO 162",<60,24,80>,48,<0.0196, 0.0196, 0.2156>,1)
label("Here are 492",y* 29.9,24*.8,<0.30196, 0.0196, 0.2156>,0)


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From: Melody
Subject: Re: Object Labels
Date: 19 Jan 2020 10:15:01
Message: <web.5e242b2b28c763ef9da690110@news.povray.org>
As for 3D point to screen xy, you'll need a few things.
POV's Perspective Matrix
InvertMatrix function
CameraMatrix 4x4

inv cam to world matrix, subv(pnt-campos)
pop world matrix

if (point[2] > 0) pop perspective matrix
which returns xy;

That's your camera.

> 0 because u dont have eyes in the back of your head.

if < 0, do nothing, move-on to the next pnt/star/object.


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From: Melody
Subject: Re: Object Labels
Date: 19 Jan 2020 11:35:00
Message: <web.5e243e3328c763ef9da690110@news.povray.org>
if you're fairly quick, u have one more question looming ---
unresolved constant of "88" -

represents a perspective cancel.

how much bigger to stay the same size at a distance?
 ... so that's your home work, resolve the last constant.


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From: Melody
Subject: Re: Object Labels
Date: 19 Jan 2020 12:20:00
Message: <web.5e24486728c763ef9da690110@news.povray.org>
"Melody" <nomail@nomail> wrote:
> if you're fairly quick, u have one more question looming ---
> unresolved constant of "88" -
>
> represents a perspective cancel.
>
> how much bigger to stay the same size at a distance?
>  ... so that's your home work, resolve the last constant.

time's up. pencil's down, a trick question doesn't require math.

88 = ground 0.

a constant.

distance at which u see object of size 1 at size 1.

perspective is all about divide by Z.
but that may not be POV, which may include near far points and doodads.

close enough tho.


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From: Melody
Subject: Re: Object Labels
Date: 19 Jan 2020 13:15:01
Message: <web.5e24553528c763ef9da690110@news.povray.org>
self adjusting to stay the same size at another FOV

fl = 1/tan(radians(fov/Aspect/2));
// fl * centerx = actual focal length

vlen / 88 becomes ...

vlen / (fl * 23.6)

or simply vlen / fl;

that was the bonus answer nobody got.


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From: kurtz le pirate
Subject: Re: Object Labels
Date: 19 Jan 2020 17:25:33
Message: <5e24910d@news.povray.org>
On 19/01/2020 07:16, Melody wrote:

> #macro label(Text,objv,r,col,top)
> #local vl = vlength(objv-campos)/88;
> #if (top)
> #local pnt = camup*(r*1.05)+objv;
> #else
> #local pnt = -camup*(vl*FontSize+r)+objv;
> #end
> #local eye = vnormalize(pnt-campos);
> object {
>    text {
>      ttf "Arial.ttf" Text 2 0
>      texture {  pigment { rgb col }  finish { ambient 1 diffuse 0 } }
>    }
>    translate x*(strlen(Text)*-0.15*FontSize)
>    scale vl*FontSize
>    Matrix_Trans(vnormalize(vcross(camup,eye)),camup,eye,pnt)
>    no_shadow
> }
> #end


Thank for this macro. It seems to be working perfectly.
My firt try with **label()**


Thanks :)

-- 
Kurtz le pirate
Compagnie de la Banquise


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