Hi,

I have a (red) cylinder, and want to add - with smooth transitions - a
number of (purple) cylinders at its end. But my understanding of the
blob object is not very good, and so i simply don't succeed.

Please see below the code as it exists now, after endless attempts.

--------------------------------------

#declare MyStrength =  2.00;
#declare MyDiameter = 150.0;

blob
{
 threshold 1.65
 cylinder { < -62.5, 0.0, 0.0 > < 62.5, 0.0, 0.0 > 500.0, 2.75 pigment {
rgb < 1, 0, 0 > } scale < 0.025, 2.105, 2.105 > translate < -60.0, 0.0,
0.0 > }
 cylinder { < -62.5, 0.0, 0.0 > < 62.5, 0.0, 0.0 > 500.0, 2.75 pigment {
rgb < 1, 0, 0 > } scale < 0.025, 2.105, 2.105 > translate <  60.0, 0.0,
0.0 > }

 cylinder { < -700.0,  100.0, 250.0 > < 700.0,  100.0, 250.0 >
MyDiameter, MyStrength pigment { rgb < 1, 0, 1 > } scale < 10.0, 1.0,
1.0 >  }
 cylinder { < -700.0,  050.0, 250.0 > < 700.0,  050.0, 250.0 >
MyDiameter, MyStrength pigment { rgb < 1, 0, 1 > } }
 cylinder { < -700.0,  000.0, 250.0 > < 700.0,  000.0, 250.0 >
MyDiameter, MyStrength pigment { rgb < 1, 0, 1 > } }
 cylinder { < -700.0, -050.0, 250.0 > < 700.0, -050.0, 250.0 >
MyDiameter, MyStrength pigment { rgb < 1, 0, 1 > } }
 cylinder { < -700.0, -100.0, 250.0 > < 700.0, -100.0, 250.0 >
MyDiameter, MyStrength pigment { rgb < 1, 0, 1 > } }

 cylinder { < -700.0,  100.0, 300.0 > < 700.0,  100.0, 300.0 >
MyDiameter, MyStrength pigment { rgb < 1, 0, 1 > } }
 cylinder { < -700.0,  050.0, 300.0 > < 700.0,  050.0, 300.0 >
MyDiameter, MyStrength pigment { rgb < 1, 0, 1 > } }
 cylinder { < -700.0,  000.0, 300.0 > < 700.0,  000.0, 300.0 >
MyDiameter, MyStrength pigment { rgb < 1, 0, 1 > } }
 cylinder { < -700.0, -050.0, 300.0 > < 700.0, -050.0, 300.0 >
MyDiameter, MyStrength pigment { rgb < 1, 0, 1 > } }
 cylinder { < -700.0, -100.0, 300.0 > < 700.0, -100.0, 300.0 >
MyDiameter, MyStrength pigment { rgb < 1, 0, 1 > } }

 cylinder { < -700.0,  100.0, 350.0 > < 700.0,  100.0, 350.0 >
MyDiameter, MyStrength pigment { rgb < 1, 0, 1 > } }
 cylinder { < -700.0,  050.0, 350.0 > < 700.0,  050.0, 350.0 >
MyDiameter, MyStrength pigment { rgb < 1, 0, 1 > } }
 cylinder { < -700.0,  000.0, 350.0 > < 700.0,  000.0, 350.0 >
MyDiameter, MyStrength pigment { rgb < 1, 0, 1 > } }
 cylinder { < -700.0, -050.0, 350.0 > < 700.0, -050.0, 350.0 >
MyDiameter, MyStrength pigment { rgb < 1, 0, 1 > } }
 cylinder { < -700.0, -100.0, 350.0 > < 700.0, -100.0, 350.0 >
MyDiameter, MyStrength pigment { rgb < 1, 0, 1 > } }

 cylinder { < -700.0,  100.0, 400.0 > < 700.0,  100.0, 400.0 >
MyDiameter, MyStrength pigment { rgb < 1, 0, 1 > } }
 cylinder { < -700.0,  050.0, 400.0 > < 700.0,  050.0, 400.0 >
MyDiameter, MyStrength pigment { rgb < 1, 0, 1 > } }
 cylinder { < -700.0,  000.0, 400.0 > < 700.0,  000.0, 400.0 >
MyDiameter, MyStrength pigment { rgb < 1, 0, 1 > } }
 cylinder { < -700.0, -050.0, 400.0 > < 700.0, -050.0, 400.0 >
MyDiameter, MyStrength pigment { rgb < 1, 0, 1 > } }
 cylinder { < -700.0, -100.0, 400.0 > < 700.0, -100.0, 400.0 >
MyDiameter, MyStrength pigment { rgb < 1, 0, 1 > } }

 cylinder { < -700.0,  100.0, 450.0 > < 700.0,  100.0, 450.0 >
MyDiameter, MyStrength pigment { rgb < 1, 0, 1 > } }
 cylinder { < -700.0,  050.0, 450.0 > < 700.0,  050.0, 450.0 >
MyDiameter, MyStrength pigment { rgb < 1, 0, 1 > } }
 cylinder { < -700.0,  000.0, 450.0 > < 700.0,  000.0, 450.0 >
MyDiameter, MyStrength pigment { rgb < 1, 0, 1 > } }
 cylinder { < -700.0, -050.0, 450.0 > < 700.0, -050.0, 450.0 >
MyDiameter, MyStrength pigment { rgb < 1, 0, 1 > } }
 cylinder { < -700.0, -100.0, 450.0 > < 700.0, -100.0, 450.0 >
MyDiameter, MyStrength pigment { rgb < 1, 0, 1 > } }
}

cylinder { < -62.5, 0.0, 0.0 > < 62.5, 0.0, 0.0 > 500.0 pigment { rgbf <
1, 0, 0,0.5 > } }

--------------------------------------

Can you give me advises, how to create a smoother transition between the
purple and red cylinders? Thanks a lot.

Post a reply to this message

I forgot to say: the size of the red cylinder needs to be maintained.

Post a reply to this message

On 12/20/2015 02:33 AM, Sven Littkowski wrote:
> Hi,
>
> I have a (red) cylinder, and want to add - with smooth transitions - a
> number of (purple) cylinders at its end. But my understanding of the
> blob object is not very good, and so i simply don't succeed.
>
> --------------------------------------
>
> Can you give me advises, how to create a smoother transition between the
> purple and red cylinders? Thanks a lot.
>

Blobs are difficult to control precisely especially given we have only 
spheres and cylinders with which to work. Where precision shapes are 
desired, folks tend not to use them.

Given your magenta cylinders are placed so near the edge of the red one 
you wished to be a fixed radius, the red is going to bulge outward.

That said, some suggestions :

Blob only :
-------------------------
1) Move the magenta shape away from the red cylinder edge if able.
2) Use many more smaller radius magenta cylinders to reduce the bulge / 
lesson the inset distance for no bulge.
3) Perhaps you could come up with an negative strength tube made up of a 
larger negative strength cylinder mostly already neutralized by inner 
positive one(s). Complicated to get clean.
4) Surround the bulging parts with many carefully positioned negative 
strength shapes, but again the red shape wouldn't be completely 
cylindrical, though you could get quite close. The neg strength shape 
count would likely be high meaning possible impacts to parse and render 
performance.
5) I've seen mention of POV-Ray blob modeling tools, but not something 
I've used.

Shape aided / shape based
-----------------------------
6) Intersect the blob you have with a cylinder of the radius you want. 
In other words constrain the blob bulge with CSG.
7) Drop the blob approach altogether and use CSG - see, for example, the 
rounded shapes package(s) in the objects collection. With pure CSG you 
of course then need somewhat more complicated textures but looks like 
you could use a gradient pattern as a basis.
8) Meshes & UV mapping probably using a modeling tool like Blender...

(6) Is probably the quickest fix.

Bill P.

Post a reply to this message

On 12/20/2015 09:44 AM, William F Pokorny wrote:
> On 12/20/2015 02:33 AM, Sven Littkowski wrote:
>> Hi,
5a)

Posted and then thought on another blob possibility - call it 5a I 
guess. Namely, you might be able to move some or all of the magenta 
cylinders outward from the red cylinder ends to reduce any unwanted 
bulging. Likely hard to get the positioning just right & still get the 
inside corner rounding you want.

Bill P.

Post a reply to this message

Here, this is what I try to get: a very smooth transition from the large
main cylinder towards a side body with straight walls but curved edges
(made by several smaller cylinders, I guess).

Would your suggestions work for this shape?

Post a reply to this message

Attachments:
Download 'untitled-1.jpg' (48 KB)

Preview of image 'untitled-1.jpg'

POV-Ray blob modeling tool

Can you give me some names? I want to try them out. Thanks.

Post a reply to this message

Am 21.12.2015 um 03:01 schrieb Sven Littkowski:
> POV-Ray blob modeling tool
> 
> Can you give me some names? I want to try them out. Thanks.

IIRC the alternative POV-Ray exporter for Blender that "Mr" is working
on already features support for blobs.

Post a reply to this message

Am 21.12.2015 um 01:56 schrieb Sven Littkowski:
> Here, this is what I try to get: a very smooth transition from the large
> main cylinder towards a side body with straight walls but curved edges
> (made by several smaller cylinders, I guess).
> 
> Would your suggestions work for this shape?

I don't think blobs will get you there, as they are fundamentally
unsuited to get truly flat surfaces.

If you do want to follow the blob approach, an isosurface with blob-like
functions might be worth trying.

Post a reply to this message

Thanks, but wow - I have never done such before. I have no idea, how to
do such. Can you give me an example? From that, I could learn for this
particular purpose. I am not easy with blobs, and I never touched iso
surfaces yet.

Post a reply to this message

On 12/20/2015 09:01 PM, Sven Littkowski wrote:
> POV-Ray blob modeling tool
>
> Can you give me some names? I want to try them out. Thanks.
>
I'd have given you names in the response, if my old memory were up to 
it. :-)

A google search for "povray blob model" turned up povray's own, links 
page at:

http://www.povray.org/resources/links/3D_Programs/POV-Ray_Modelling_Programs/

on which some blob modeling tools are listed. Some of those links dead 
end - though further searches on the tool names found downloads.

Code seems pretty old - mid to late 90s vintage - though probably still 
functions. I'd go with Christoph's Blender recommendation for Mr's 
Blender Blobs if you want any support.

Saw the image you posted in another response which I suppose came from 
some other technique/modeler you don't want to use? In any case, I 
second Christoph's response that blobs are not the way to go if you want 
flat surfaces.

Bill P.

Post a reply to this message