Povray, shadows and mesh2 objects

Povray, shadows and mesh2 objects

Post by Eri » Wed, 23 Jul 2003 22:37:07



I have a model of a paper cup (rolled top, paper thinkness, and all).
Well it looks wonderful except for when the shadow from the rolled top
falls on the cup.  The shadow is not nice and smooth.  It is
stair-steppy since the cup is a trangle mesh2 object.  I tried
creating a invisible cup using a cone and a torus just to use for
casting shadows and using the mesh2 cup just for viewing.  However, it
seem next to impossible to line up the two cups so they render
correctly.  And to make things more difficult this will be automated
by a program that I have wrote to generate these cups and put them in
different scenes for product shots.  Is there any way to accomplish
this?  I have though about just bumping up the number of sides the
mesh2 cup has to make it rounder.  This is by far the simplest but not
the most accurate.  Thanks for any suggestions.
 
 
 

Povray, shadows and mesh2 objects

Post by Warp » Thu, 24 Jul 2003 03:54:26


  How about simply using more triangles?

--
plane{-x+y,-1pigment{bozo color_map{[0rgb x][1rgb x+y]}turbulence 1}}
sphere{0,2pigment{rgbt 1}interior{media{emission 1density{spherical
density_map{[0rgb 0][.5rgb<1,.5>][1rgb 1]}turbulence.9}}}scale
<1,1,3>hollow}text{ttf"timrom""Warp".1,0translate<-1,-.1,2>}//  - Warp -

 
 
 

Povray, shadows and mesh2 objects

Post by x43.. » Fri, 25 Jul 2003 16:51:34


On 22 July 2003 13:37 GMT, Eric wrote in

Quote:> I have a model of a paper cup (rolled top, paper thinkness, and all).
> Well it looks wonderful except for when the shadow from the rolled top
> falls on the cup.  The shadow is not nice and smooth.  It is
> stair-steppy since the cup is a trangle mesh2 object.

It sounds like you want the smooth triangles option. but I'm not sure
how to do it with a mesh2. I've only done it with a height field.
Section 3.5.2.1 (Smooth triangles and mesh2) of the Povray 3.5 manual
discusses how to do it...looks complex, but I've never messed with a
mesh2 object. Maybe you can figure it out. ;-)

Section 9.9 (Smooth triangle artifact) discusses a problem you may get
should you switch to smooth triangles. Short answer for smooth
triangles:  use double_illuminate if possible. The problem is your
paper cup may not shadow properly with this option since light may be
hitting it from both sides--you did mention the object has thickness,
so double illuminate may not be a problem.

Shadow line artifact (discussed in section 9.8) may also be part of your
problem, but it will only apply if you are using a normal modifier or
you decide to go with smooth triangles. The manual says making the
object shadowless will eliminate this artifact, but obviously you don't
want to do that. ;-)

--

 
 
 

Povray, shadows and mesh2 objects

Post by Warp » Fri, 25 Jul 2003 20:37:12



> It sounds like you want the smooth triangles option.

  Smooth triangles will not smooth the edges of the triangles. That won't
help.

--
plane{-x+y,-1pigment{bozo color_map{[0rgb x][1rgb x+y]}turbulence 1}}
sphere{0,2pigment{rgbt 1}interior{media{emission 1density{spherical
density_map{[0rgb 0][.5rgb<1,.5>][1rgb 1]}turbulence.9}}}scale
<1,1,3>hollow}text{ttf"timrom""Warp".1,0translate<-1,-.1,2>}//  - Warp -

 
 
 

Povray, shadows and mesh2 objects

Post by Eri » Thu, 31 Jul 2003 05:56:10



> How about simply using more triangles?

Well that is what I am doing now.  I have increased the number sides
of the cup from 30 to 60.  I will probly increase it again because the
shadow artifacts are still noticeable.  I was just wondering if anyone
new of a better way than this brute force method.
 
 
 

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Thank you

Johan

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