Hi guys,

I am working on a project where I am trying to render an impossible cube. The
final stage is to animate it but initially, I would only like to see if I can
make a part of the cube invisible. The logic I'm following is that, every time
part of the cube skeleton is hidden by some other part of it that's in front,
make that part invisible so that the part on the back is still shown. this will
give the illusion of an impossible cube. Is there any way you could suggest I
can do this?
Thank you in advance.

Alex

Post a reply to this message

On 7-11-2012 14:06, Encore wrote:
> Hi guys,
>
> I am working on a project where I am trying to render an impossible cube. The
> final stage is to animate it but initially, I would only like to see if I can
> make a part of the cube invisible. The logic I'm following is that, every time
> part of the cube skeleton is hidden by some other part of it that's in front,
> make that part invisible so that the part on the back is still shown. this will
> give the illusion of an impossible cube. Is there any way you could suggest I
> can do this?
> Thank you in advance.
>
> Alex
>
>
Yes, you could use interior_texture.

Example (not tried):

box {
  -1, 1
  texture {pigment {rgbt 1}}
  interior_texture {pigment {rgb 1}}
}

Thomas

Post a reply to this message

On 07/11/2012 1:06 PM, Encore wrote:
> Hi guys,
>
> I am working on a project where I am trying to render an impossible cube. The
> final stage is to animate it but initially, I would only like to see if I can
> make a part of the cube invisible. The logic I'm following is that, every time
> part of the cube skeleton is hidden by some other part of it that's in front,
> make that part invisible so that the part on the back is still shown. this will
> give the illusion of an impossible cube. Is there any way you could suggest I
> can do this?
> Thank you in advance.

I think that you will need to use some clever maths and use differences.
I had a quick try with that method and it might work.

-- 
Regards
     Stephen

Post a reply to this message

Stephen <mca### [at] aolcom> wrote:
> On 07/11/2012 1:06 PM, Encore wrote:
> > Hi guys,
> >
> > I am working on a project where I am trying to render an impossible cube. The
> > final stage is to animate it but initially, I would only like to see if I can
> > make a part of the cube invisible. The logic I'm following is that, every time
> > part of the cube skeleton is hidden by some other part of it that's in front,
> > make that part invisible so that the part on the back is still shown. this will
> > give the illusion of an impossible cube. Is there any way you could suggest I
> > can do this?
> > Thank you in advance.
>
> I think that you will need to use some clever maths and use differences.
> I had a quick try with that method and it might work.
>
> --
> Regards
>      Stephen


The code block for my cube wireframe construction is this:

sphere{<0,0,0>,1 hollow
       texture{pigment{gradient <0,1,0>
                       color_map{[0    color Blue]
                  [0.45 color White]
                  [0.55 color White]
                  [1.0  color Blue]}
       scale 2 translate<0,-1,0>}
               finish {ambient 1 diffuse 0} }
       scale 10000}
// ground-----------------------------------------------------------
/*plane{ <0,1,0>, 0
       texture{ pigment { checker color Gray65 color Gray30}
                normal  { bumps 0.5 scale 0.05  }
                finish  { phong 0.1 }
              } // end of texture
     }  */
#declare R = 0.25;   //radius of the tubes
#declare r = 0.375;  //radius of the spheres
#declare BigCube1 = merge{
sphere{<-1,-1,-1>,r}  sphere{< 1,-1,-1>,r}
sphere{<-1,-1, 1>,r}  sphere{< 1,-1, 1>,r}
sphere{<-1, 1,-1>,r}  sphere{< 1, 1,-1>,r}
sphere{<-1, 1, 1>,r}  sphere{< 1, 1, 1>,r}
cylinder {<-1,-1,-1>,< 1,-1,-1>,R}// 4 in x direction
cylinder {<-1,-1, 1>,< 1,-1, 1>,R}
cylinder {<-1, 1,-1>,< 1, 1,-1>,R}
cylinder {<-1, 1, 1>,< 1, 1, 1>,R}
cylinder {<-1,-1,-1>,<-1, 1,-1>,R}// 4 in y direction
cylinder {<-1,-1, 1>,<-1, 1, 1>,R}
cylinder {< 1,-1,-1>,< 1, 1,-1>,R}
cylinder {< 1,-1, 1>,< 1, 1, 1>,R}
cylinder {<-1,-1,-1>,<-1,-1, 1>,R}// 4 in z direction
cylinder {<-1, 1,-1>,<-1, 1, 1>,R}
cylinder {< 1,-1,-1>,< 1,-1, 1>,R}
cylinder {< 1, 1,-1>,< 1, 1, 1>,R}

texture {
       T_Gold_1B// pigment{Red filter .98}
      finish { ambient 0.2 diffuse 0.7 }
    }
}
object{ BigCube1 scale 0.7
        rotate<0,60,0> translate<0,1.2,0>}


Other than that, I just can't figure out how to "scan" a piece on the back and
make the front part that's hiding it transparent. After all, I can't make a
completely automated method for this as there are several edges which should not
be hidden at all. (If you render this code with some camera settings like
global_settings{ assumed_gamma 1.0 }
#default{ finish{ ambient 0.1 diffuse 0.9 }}

#include "colors.inc"
#include "textures.inc"
#include "golds.inc"
#declare Cam0 =camera {ultra_wide_angle angle 60
                       location  <0.0 , 3.0 ,-3.5>
                       look_at   <0.0 , 1.0 , 0.0>}
/*#declare Cam1 =camera {ultra_wide_angle angle 250
                       location  <0.0 , 0.5 ,-2.5>
                       look_at   <0.2 , 1.0 , 0.0>}*/
camera{Cam0}
light_source{<1500,2000,-2500> color White*0.7}

you will see exactly what I mean.)

Post a reply to this message

On 07/11/2012 3:33 PM, Encore wrote:
> If you render this code with

Sorry, I am so busy in RL that it might/will take me a while to get 
round to it. :-(
Most optical illusions rely on a fixed viewpoint and I think that this 
would be very difficult to create in an animation.
But it would be very worthwhile if it can be done.
One of the reasons that I think that you would need differences is that 
not all the surfaces that hide the back of the object are invisible. For 
instances at the corners.
If I have the time at the weekend I will look into it further.

-- 
Regards
     Stephen

Post a reply to this message

Stephen <mca### [at] aolcom> wrote:
> On 07/11/2012 3:33 PM, Encore wrote:
> > If you render this code with
>
> Sorry, I am so busy in RL that it might/will take me a while to get
> round to it. :-(
> Most optical illusions rely on a fixed viewpoint and I think that this
> would be very difficult to create in an animation.
> But it would be very worthwhile if it can be done.
> One of the reasons that I think that you would need differences is that
> not all the surfaces that hide the back of the object are invisible. For
> instances at the corners.
> If I have the time at the weekend I will look into it further.
>
> --
> Regards
>      Stephen

Thanks Steve I really appreciate it. But put animation aside (I'll try and deal
with this later on), how can I make a fixed part of this object invisible? I
mean a way is to make a difference as you are saying, another is to trace and
return a transparent value for a specific part of an edge. Do you have any code
for achieving this in a static state like the one I'm dealing with here?

Post a reply to this message

On 07/11/2012 7:41 PM, Encore wrote:
> Thanks Steve I really appreciate it. But put animation aside (I'll try and deal
> with this later on), how can I make a fixed part of this object invisible? I
> mean a way is to make a difference as you are saying,

Okay, I did make an attempt and the code is below. But be aware that I 
use a modeller (Bishop3d) and the code is not good Pov-Ray code. (I have 
to put single objects in a union to get the desired effect. Nor is it 
optimised. (machine written code sucks ;-) )

> another is to trace and
> return a transparent value for a specific part of an edge. Do you have any code
> for achieving this in a static state like the one I'm dealing with here?

This I would say is more of a general or advanced topic.

#version 3.6;

background { colour rgb <0.000,0.000,0.000> }

// 
****************************************************************************
// referenced scene items and forced visible scene items declaration begin
// 
****************************************************************************

#declare Default_Texture0 =
texture {
    pigment {
       colour rgbft <1.000,0.000,1.000,0.000,0.000>
    }

    finish {
       ambient     rgb <1.000,1.000,1.000>
       brilliance  1.000
       crand       0.000
       diffuse     0.600
       metallic    0.000
       phong       0.000
       phong_size  40.000
       specular    0.000
       roughness   0.050
    }

}

#default{ texture{ Default_Texture0 } }

#declare Shadow_Clouds_Top =
pigment {
    colour rgbft <0.196,0.600,0.800,0.000,0.000>
}

#declare Shadow_Clouds_Bot =
pigment {
    bozo
    colour_map {
       [0.000 rgbft <0.850,0.850,0.850,0.000,0.000>]
       [0.100 rgbft <0.750,0.750,0.750,0.000,0.000>]
       [0.500 rgbft <1.000,1.000,1.000,0.000,1.000>]
    }

    rotate    <0.0,0.0,90.000>
    rotate    <180.000,0.0,0.0>
    scale     <0.200,1.200,1.200>
    rotate    <-180.000,0.000,-90.000>
    rotate    <0.000,355.000,0.000>
    translate <0.000,-0.150,-0.000>
    turbulence <0.650,0.650,0.650>
    octaves 6
    lambda 2.000
    omega 0.700
}

#declare Shadow_Clouds_Mid =
pigment {
    bozo
    colour_map {
       [0.000 rgbft <0.850,0.850,0.850,0.000,0.000>]
       [0.100 rgbft <0.750,0.750,0.750,0.000,0.000>]
       [0.500 rgbft <1.000,1.000,1.000,0.000,1.000>]
    }

    rotate    <0.0,0.0,90.000>
    rotate    <180.000,0.0,0.0>
    scale     <0.200,1.200,1.200>
    rotate    <-180.000,0.000,-90.000>
    rotate    <0.000,355.000,0.000>
    turbulence <0.650,0.650,0.650>
    octaves 6
    lambda 2.000
    omega 0.700
}

#declare Blue_White_Tiles1 =
texture {
    checker
    texture {
       pigment {
          colour rgbft <1.000,1.000,1.000,0.000,0.000>
       }

       normal {
          agate, 0.100
          agate_turb 0.500
       }

       finish {
          ambient     rgb <0.100,0.100,0.100>
          brilliance  1.000
          crand       0.000
          diffuse     0.600
          metallic    0.000
          phong       0.000
          phong_size  40.000
          specular    0.000
          roughness   0.249
          reflection {
             rgb <0.100,0.100,0.100>, rgb <0.000,0.000,0.000>
             fresnel   0
             falloff   0.000
             exponent  1.000
             metallic  0.000
          }
       }

    }

    texture {
       pigment {
          colour rgbft <0.000,0.502,1.000,0.000,0.000>
       }

       normal {
          agate, 0.100
          agate_turb 0.500
       }

       finish {
          ambient     rgb <0.100,0.100,0.100>
          brilliance  1.000
          crand       0.000
          diffuse     0.600
          metallic    0.000
          phong       0.000
          phong_size  40.000
          specular    0.000
          roughness   0.249
          reflection {
             rgb <0.100,0.100,0.100>, rgb <0.000,0.000,0.000>
             fresnel   0
             falloff   0.000
             exponent  1.000
             metallic  0.000
          }
       }

    }

    rotate    <0.0,0.0,180.000>
    rotate    <-90.000,0.0,0.0>
    scale     <-300.000,-300.000,-1000.000>
    rotate    <90.000,0.000,-180.000>
    rotate    <0.000,-180.000,0.000>
    scale     <0.010,0.010,0.010>
}

#declare Maple =
material{
    texture {
       #declare BISHOP3D_TEMPORARY_IDENTIFIER =
          texture {
             pigment {
                wood
                colour_map {
                   [0.000 rgbft <0.796,0.796,0.384,0.000,0.000>]
                   [0.133 rgbft <0.706,0.518,0.235,0.000,0.000>]
                   [0.230 rgbft <0.796,0.796,0.384,0.000,0.000>]
                   [0.336 rgbft <0.706,0.518,0.235,0.000,0.000>]
                   [0.442 rgbft <0.796,0.796,0.384,0.000,0.000>]
                   [0.549 rgbft <0.706,0.518,0.235,0.000,0.000>]
                   [0.646 rgbft <0.796,0.796,0.384,0.000,0.000>]
                   [0.743 rgbft <0.706,0.518,0.235,0.000,0.000>]
                   [0.850 rgbft <0.796,0.796,0.384,0.000,0.000>]
                   [0.947 rgbft <0.706,0.518,0.235,0.000,0.000>]
                   [1.000 rgbft <0.796,0.796,0.384,0.000,0.000>]
                }

                frequency 1.000
                phase 0.000
                ramp_wave
                noise_generator 1
                rotate    <0.0,0.0,180.000>
                scale     <2.000,2.000,15.000>
                rotate    <0.000,0.000,-180.000>
                rotate    <0.000,0.000,90.000>
                translate <-8.000,80.000,0.000>
                turbulence <0.100,0.100,0.100>
                octaves 6
                lambda 2.000
                omega 0.500
             }

             finish {
                ambient     rgb <0.200,0.200,0.200>
                brilliance  1.000
                crand       0.000
                diffuse     0.800
                metallic    0.000
                phong       0.000
                phong_size  40.000
                specular    0.000
                roughness   0.050
             }

          }
          texture {
             pigment {
                bozo
                colour_map {
                   [0.000 rgbft <1.000,1.000,0.439,1.000,0.000>]
                   [0.008 rgbft <1.000,1.000,0.439,1.000,0.000>]
                   [0.508 rgbft <1.000,1.000,0.439,0.400,0.000>]
                   [1.000 rgbft <1.000,1.000,0.439,1.000,0.000>]
                }

                rotate    <0.0,0.0,180.000>
                scale     <1.500,1.500,0.375>
                rotate    <0.000,0.000,-180.000>
                rotate    <0.000,0.000,90.000>
             }

             finish {
                ambient     rgb <0.200,0.200,0.200>
                brilliance  1.000
                crand       0.000
                diffuse     0.800
                metallic    0.000
                phong       0.000
                phong_size  40.000
                specular    0.000
                roughness   0.050
             }

          }
       ;// the semicolon is necessary or POV-Ray will not figure out 
that the declarations has ended
       BISHOP3D_TEMPORARY_IDENTIFIER
    }

}

#declare Camera0 =
camera {
    perspective
    location <18.112,45.490,-94.622>
    up y
    right 1.333*x
    angle 33.000
    sky <-0.061,0.944,0.325>
    look_at < 0.334, 11.721, -0.011 >
}  // end Camera0

#declare Box5 =
box {
    < -0.5000000, -0.5000000, -0.5000000 >, < 0.5000000, 0.5000000, 
0.5000000 >
    material{ Maple }
    scale     <12.000000,2.000000,2.000000>
}  // end Box5


// 
****************************************************************************
// referenced scene items and forced visible scene items declaration end
// 
****************************************************************************

union {  // Lights
    light_source {  // Shadowless_Light_Source0
       < 0.000000, 0.000000, 0.000000 >, colour rgb <1.000,1.000,1.000>
       fade_power 0.000
       fade_distance 100.000
       media_attenuation off
       media_interaction on
       shadowless
       translate <15.811000,100.000000,-200.977356>
    }  // end Shadowless_Light_Source0

    light_source {  // Light_Source0
       < 0.000000, 0.000000, 0.000000 >, colour rgb <1.000,1.000,1.000>
       fade_power 0.000
       fade_distance 100.000
       media_attenuation off
       media_interaction on
       translate <-24.636320,55.859425,-195.075000>
    }  // end Light_Source0

}  // end Lights

sky_sphere {  // SkySphere1
    pigment{ Shadow_Clouds_Top }
    pigment{ Shadow_Clouds_Mid }
    pigment{ Shadow_Clouds_Bot }

}  // end SkySphere1

plane {  // Plane1
    y , 0
    texture{ Blue_White_Tiles1 }
}  // end Plane1

union {  // Centre_0
    difference {  // CSG12
       union {  // Front0
          union {  // CSG3
             box {  // Box3
                < -0.5000000, -0.5000000, -0.5000000 >, < 0.5000000, 
0.5000000, 0.5000000 >
                material{ Maple }
                scale     <12.000000,2.000000,2.000000>
             }  // end Box3

             rotate    <1.000000,0.000000,90.000000>
             translate <7.000000,0.000000,0.000000>
          }  // end CSG3

          union {  // CSG2
             box {  // Box2
                < -0.5000000, -0.5000000, -0.5000000 >, < 0.5000000, 
0.5000000, 0.5000000 >
                material{ Maple }
                scale     <12.000000,2.000000,2.000000>
             }  // end Box2

             rotate    <1.000000,0.000000,90.000000>
             translate <-7.000000,0.000000,0.000000>
          }  // end CSG2

          union {  // CSG1
             box {  // Box1
                < -0.5000000, -0.5000000, -0.5000000 >, < 0.5000000, 
0.5000000, 0.5000000 >
                material{ Maple }
                scale     <16.000000,2.000000,2.000000>
             }  // end Box1

             translate <0.000000,7.000000,0.000000>
          }  // end CSG1

          union {  // CSG0
             box {  // Box0
                < -0.5000000, -0.5000000, -0.5000000 >, < 0.5000000, 
0.5000000, 0.5000000 >
                material{ Maple }
                scale     <16.000000,2.000000,2.000000>
             }  // end Box0

             translate <0.000000,-7.000000,0.000000>
          }  // end CSG0

          translate <0.000000,0.000000,-7.000000>
       }  // end Front0

       union {  // CSG13
          object {  // Reference0
             Box5
             scale     <1.052000,1.300000,13.719000>
             rotate    <-34.824000,0.000000,90.000000>
             translate <5.262000,1.848000,-7.674000>
          }  // end Reference0

          rotate    <0.000000,-1.223000,0.000000>
          translate <-6.886000,0.000000,7.050000>
       }  // end CSG13

    }  // end CSG12

    union {  // Side1
       union {  // CSG10
          box {  // Box10
             < -0.5000000, -0.5000000, -0.5000000 >, < 0.5000000, 
0.5000000, 0.5000000 >
             material{ Maple }
             scale     <12.000000,2.000000,2.000000>
          }  // end Box10

          rotate    <1.000000,0.000000,90.000000>
          translate <7.000000,0.000000,0.000000>
       }  // end CSG10

       union {  // CSG11
          box {  // Box11
             < -0.5000000, -0.5000000, -0.5000000 >, < 0.5000000, 
0.5000000, 0.5000000 >
             material{ Maple }
             scale     <12.000000,2.000000,2.000000>
          }  // end Box11

          rotate    <1.000000,0.000000,90.000000>
          translate <-7.000000,0.000000,0.000000>
       }  // end CSG11

       rotate    <90.000000,0.000000,0.000000>
       translate <0.000000,7.000000,0.000000>
    }  // end Side1

    union {  // Side0
       union {  // CSG8
          box {  // Box8
             < -0.5000000, -0.5000000, -0.5000000 >, < 0.5000000, 
0.5000000, 0.5000000 >
             material{ Maple }
             scale     <12.000000,2.000000,2.000000>
          }  // end Box8

          rotate    <1.000000,0.000000,90.000000>
          translate <7.000000,0.000000,0.000000>
       }  // end CSG8

       union {  // CSG9
          box {  // Box9
             < -0.5000000, -0.5000000, -0.5000000 >, < 0.5000000, 
0.5000000, 0.5000000 >
             material{ Maple }
             scale     <12.000000,2.000000,2.000000>
          }  // end Box9

          rotate    <1.000000,0.000000,90.000000>
          translate <-7.000000,0.000000,0.000000>
       }  // end CSG9

       rotate    <90.000000,0.000000,0.000000>
       translate <0.000000,-7.000000,0.000000>
    }  // end Side0

    union {  // Back0
       union {  // CSG4
          box {  // Box4
             < -0.5000000, -0.5000000, -0.5000000 >, < 0.5000000, 
0.5000000, 0.5000000 >
             material{ Maple }
             scale     <12.000000,2.000000,2.000000>
          }  // end Box4

          rotate    <1.000000,0.000000,90.000000>
          translate <7.000000,0.000000,0.000000>
       }  // end CSG4

       union {  // CSG5
          object{ Box5 }

          rotate    <1.000000,0.000000,90.000000>
          translate <-7.000000,0.000000,0.000000>
       }  // end CSG5

       union {  // CSG6
          box {  // Box6
             < -0.5000000, -0.5000000, -0.5000000 >, < 0.5000000, 
0.5000000, 0.5000000 >
             material{ Maple }
             scale     <16.000000,2.000000,2.000000>
          }  // end Box6

          translate <0.000000,7.000000,0.000000>
       }  // end CSG6

       union {  // CSG7
          box {  // Box7
             < -0.5000000, -0.5000000, -0.5000000 >, < 0.5000000, 
0.5000000, 0.5000000 >
             material{ Maple }
             scale     <16.000000,2.000000,2.000000>
          }  // end Box7

          translate <0.000000,-7.000000,0.000000>
       }  // end CSG7

       translate <0.000000,0.000000,7.000000>
    }  // end Back0

    rotate    <0.000000,24.200000,0.000000>
    translate <0.000000,8.000000,0.000000>
}  // end Centre_0


camera{ Camera0 }


-- 
Regards
     Stephen

Post a reply to this message

Stephen <mca### [at] aolcom> wrote:
> On 07/11/2012 7:41 PM, Encore wrote:
> > Thanks Steve I really appreciate it. But put animation aside (I'll try and deal
> > with this later on), how can I make a fixed part of this object invisible? I
> > mean a way is to make a difference as you are saying,
>
> Okay, I did make an attempt and the code is below. But be aware that I
> use a modeller (Bishop3d) and the code is not good Pov-Ray code. (I have
> to put single objects in a union to get the desired effect. Nor is it
> optimised. (machine written code sucks ;-) )
>
> > another is to trace and
> > return a transparent value for a specific part of an edge. Do you have any code
> > for achieving this in a static state like the one I'm dealing with here?
>
> This I would say is more of a general or advanced topic.
>

Wow man this looks really awesome for an initial state of what I'm trying to
achieve! A few modification needed to be made in the rotation and scale values
for the difference box (and still having a small gap there that's visible), but
other than that this looks great! Thanks a lot

Post a reply to this message

Stephen <mca### [at] aolcom> wrote:
> On 07/11/2012 7:41 PM, Encore wrote:
> > Thanks Steve I really appreciate it. But put animation aside (I'll try and deal
> > with this later on), how can I make a fixed part of this object invisible? I
> > mean a way is to make a difference as you are saying,
>
> Okay, I did make an attempt and the code is below. But be aware that I
> use a modeller (Bishop3d) and the code is not good Pov-Ray code. (I have
> to put single objects in a union to get the desired effect. Nor is it
> optimised. (machine written code sucks ;-) )
>
> > another is to trace and
> > return a transparent value for a specific part of an edge. Do you have any code
> > for achieving this in a static state like the one I'm dealing with here?
>
> This I would say is more of a general or advanced topic.
>

Wow man this looks really awesome for an initial state of what I'm trying to
achieve! A few modification needed to be made in the rotation and scale values
for the difference box (and still having a small gap there that's visible), but
other than that this looks great! Thanks a lot

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Encore wrote:

> Hi guys,
> 
> I am working on a project where I am trying to render an impossible cube.
> The final stage is to animate it but initially, I would only like to see
> if I can make a part of the cube invisible. The logic I'm following is
> that, every time part of the cube skeleton is hidden by some other part of
> it that's in front, make that part invisible so that the part on the back
> is still shown. this will give the illusion of an impossible cube. Is
> there any way you could suggest I can do this?
> Thank you in advance.
> 
> Alex

Check out p.b.images.
I still need to clean up the code before I can post it.

-- 
Ger

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