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Hi All:
Just a quick scene to try to get back at "just for fun" raytracing...
The grass is a very old code of mine based on SDL-created meshes,
revised now to add uv mapping. The texture is a leaf picture from
mayang.com.
The scene is surrounded with a cloudy HDRI sky, and the lighting as
reinforced with just a big area light above.
The drops are blobs traced() from above, but they don't take yet into
account how wide it's the grass blade they rest on... that should be the
next and final step.
This image is postprocessed with Gimp to add together two renders:
one with just pigments, and another with reflections and micro-normals
but without lighting (combined render times were about 2h).
--
Jaime Vives Piqueres
La Persistencia de la Ignorancia
http://www.ignorancia.org
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Attachments:
Download 'grass-pp-03.jpg' (295 KB)
Preview of image 'grass-pp-03.jpg'
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Jaime Vives Piqueres <jai### [at] ignorancia org> wrote:
> Hi All:
>
> Just a quick scene to try to get back at "just for fun" raytracing...
>
> The grass is a very old code of mine based on SDL-created meshes,
> revised now to add uv mapping. The texture is a leaf picture from
> mayang.com.
>
> The scene is surrounded with a cloudy HDRI sky, and the lighting as
> reinforced with just a big area light above.
>
> The drops are blobs traced() from above, but they don't take yet into
> account how wide it's the grass blade they rest on... that should be the
> next and final step.
>
> This image is postprocessed with Gimp to add together two renders:
> one with just pigments, and another with reflections and micro-normals
> but without lighting (combined render times were about 2h).
>
> --
> Jaime Vives Piqueres
>
> La Persistencia de la Ignorancia
> http://www.ignorancia.org
Looks very nice. Obviously this is new, never been cut grass though :)
One thing I had tried a few years ago was similar, and placed and sized the
grass based on a pigment evalution like bozo. You could then apply a translate
to the pattern for an animation that could simulate wind blowing.
-tgq
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Great texture on the grass, if it wasn't posted on this forum I would have just
assumed it was a photo but at closer inspection I think some of the rain drops
are a bit too spherical for their position on the grass.
Sean
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> Great texture on the grass, if it wasn't posted on this forum I would have just
> assumed it was a photo but at closer inspection I think some of the rain drops
> are a bit too spherical for their position on the grass.
>
> Sean
>
>
There is also some visible fasceting on the blades.
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The grass is superb, I really like it. The drops are indeed a bit spherical as
"s day" mentioned. And some are a bit displaced, hanging on the edges of the
blades. I think that is what you meant with taking the width of the blades into
account.
My idea to address this both issues is to trace() 4 times at the "edges" of a
drop (4 points orthogonal in the ground plane at the boundary of the drops) to
find a place completely on a blade. Perhaps you can determine the general slope
of the blade from this points and place a little bit scaled and rotated version
of a drop. I know, this is easily said and much harder to accomplish... But...,
it was my first idea to the problem.
Regards,
Michael
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Second thought: 4 points are one to much. Better use only 3 in a equiliteral
traingle at the borders of the drops. Then the plane between this points on the
blade is well defined (4 points may not result in a plane) and the slopes can be
calculated.
Regards,
Michael
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"Jaime Vives Piqueres" <jai### [at] ignoranciaorg> schreef in bericht
news:4dc3d9a6@news.povray.org...
> The drops are blobs traced() from above, but they don't take yet into
> account how wide it's the grass blade they rest on... that should be the
> next and final step.
>
Maybe not *all* grass, but generally the blades are a tiny bit folded around
a central - longitudinal - nerve. This helps also the blade to keep upright.
Water droplets then often concentrate in the fold.
Thomas
Post a reply to this message
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"Thomas de Groot" <tDOTdegroot@interDOTnlANOTHERDOTnet> schreef in bericht
news:4dccda2d$1@news.povray.org...
> Maybe not *all* grass, but generally the blades are a tiny bit folded
> around a central - longitudinal - nerve. This helps also the blade to keep
> upright. Water droplets then often concentrate in the fold.
...but when I google grass blade images, they often do not seem to do what I
would like them to do.... ;-)
Thomas
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Am 12.05.2011 22:25, schrieb TawnyOwl:
> Second thought: 4 points are one to much. Better use only 3 in a equiliteral
> traingle at the borders of the drops. Then the plane between this points on the
> blade is well defined (4 points may not result in a plane) and the slopes can be
> calculated.
For determining the "slope" of the blade, retrieving the normal vector
from a single trace() call should suffice.
Tracing multiple rays is a good idea though to prevent drops from
hanging out too far at a blade edge.
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> Great texture on the grass, if it wasn't posted on this forum I would
> have just assumed it was a photo but at closer inspection I think
> some of the rain drops are a bit too spherical for their position on
> the grass.
>
Yes, that's another problem apart from the placement on the blade
borders... I'm already using a blob with two components, the one below
having negative strength to make it look less spherical, but it isn't
doing a very good job (I admit that I didn't put much effort into it).
--
Jaime Vives Piqueres
La Persistencia de la Ignorancia
http://www.ignorancia.org
Post a reply to this message
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