Shadows of partially transparent textures

Shadows of partially transparent textures

Post by Dirk Wrockla » Wed, 21 Jul 1999 04:00:00



Hi,

I've tried to cover a sphere with a partially transparent png image with
PoVRay 3.1e. That gives nice results - except for the shadow of the
sphere. The shadow is completely dark, i.e. it has no bright "holes" which
should result from the transparent parts of the texture.

Is that a bug in PoVRay or have I missed something?

Thanks in advance,

Dirk Wrocklage
--
      ___________________________________________________
     / Dirk Wrocklage              University of        /

    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 
 
 

Shadows of partially transparent textures

Post by Ken » Wed, 21 Jul 1999 04:00:00



> Hi,

> I've tried to cover a sphere with a partially transparent png image with
> PoVRay 3.1e. That gives nice results - except for the shadow of the
> sphere. The shadow is completely dark, i.e. it has no bright "holes" which
> should result from the transparent parts of the texture.

> Is that a bug in PoVRay or have I missed something?

> Thanks in advance,

> Dirk Wrocklage
> --

  When specifying the image map you need to specify the transparent
portion of the images pallet with a filter or transmit value. For
example you have all the white areas of the image your transparent
areas the image map statement should look something like this:

 sphere { <0,0,0>,1
  pigment {
   image_map { png "your_image.png interpolate 2 filter 255, 1 }
     translate -0.5
     scale 2
  }
 }

 Another important point is that the png cannot be at greater than a
256 color 8 bit image or it will not work. 24 and 16 bit images are
not supported with these features.

--
Ken Tyler


http://home.pacbell.net/tylereng/links.htm

 
 
 

Shadows of partially transparent textures

Post by Dirk Wrockla » Thu, 29 Jul 1999 04:00:00




Quote:>   When specifying the image map you need to specify the transparent
> portion of the images pallet with a filter or transmit value. For
> example you have all the white areas of the image your transparent
> areas the image map statement should look something like this:

> [...]

>  Another important point is that the png cannot be at greater than a
> 256 color 8 bit image or it will not work. 24 and 16 bit images are
> not supported with these features.

Are you sure? I've noticed that the shadows are correct if the 'once'
keyword is given in the texture-statement. Without the 'once', the shadows
are corrupt - it doesn't matter which depth the image has or if you
specify a transmit value. I still think that this is a PoVRay-Bug.

Thanks,

    Dirk
--
      ___________________________________________________
     / Dirk Wrocklage              University of        /

    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 
 
 

1. Sample code for partially transparent textures urgently needed

I'm looking for sample code that shows me how to realize
partially transparent textures e.g. to visualize trees in a
graphical world. The technique I would like to use is called
"billboarding" in the "Open GL Programming Guide".

Any help is appreciated

- Jrgen

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