Hi All,
I have been having problems rendering a glossy bumpy surface composed of intersecting ellipsoids illuminated under a rectangular light source. The image appears to contain some random point source reflections on the surface in addition to the direct reflection of the area light.
To view the rendered image, see: http://homepages.nyu.edu/~yxh201/bumpysurftest.jpg.
The bumpy surface is made of the following material:
void plastic gray_plastic
0
5 .2 .2 .2 .1482 0
and a 30x24 flat rectangular light source is defined as:
void light bright
0
3 25 25 25
I use the following parameters to render the scene:
-ab 2 -aa .08 -ad 1024 -as 512 -av .2 .2 .2 -sj 1 -st .01 -dj 1 -ds .05
Any suggestions to clean up the "noise" in the image? Much thanks...
--xian
Hi Xian,
Interesting surface geometry you have there. Based on your material description though the results you are getting seem to be fine. The so-called "noise" that you are seeing is the specular highlights based on the material that you defined. The plastic material that you defined only has a specular component you have left the roughness parameter set to 0, thus you material is "shiny" so you are getting the tightly defined specular highlights on the bumps of the geometry.
If you want a "glossy" (not sure exactly what you mean here as this covers a variety of things) finish, then you should add a roughness parameter, for example, you could try out the following for starters (this is not based on anything in particular) to see what the difference is:
The bumpy surface is made of the following material:
void plastic gray_plastic
0
5 .2 .2 .2 .1 .1
I would try this out with the parameters that you have and see what you get. As an additional experiment you may also want to turn on true random monte carlo sampling by setting -u+, though this may require that you oversample your image at a higher size.
-Jack
PS - what does the geometry represent?
Yun-Xian Ho wrote:
···
Hi All,
I have been having problems rendering a glossy bumpy surface composed of intersecting ellipsoids illuminated under a rectangular light source. The image appears to contain some random point source reflections on the surface in addition to the direct reflection of the area light.
To view the rendered image, see: http://homepages.nyu.edu/~yxh201/bumpysurftest.jpg.
The bumpy surface is made of the following material:
void plastic gray_plastic
0
5 .2 .2 .2 .1482 0
and a 30x24 flat rectangular light source is defined as:
void light bright
0
3 25 25 25
I use the following parameters to render the scene:
-ab 2 -aa .08 -ad 1024 -as 512 -av .2 .2 .2 -sj 1 -st .01 -dj 1 -ds .05
Any suggestions to clean up the "noise" in the image? Much thanks...
--xian
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# visarc incorporated
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Hi Xian,
Adding to Jack's comments, I think you will see what appears as noise no matter what you do. The minification that happens on multiple reflections makes your light source into a dot. In other words, in the reflection of one sphere you see more spheres. The miniaturized image of the light source becomes a microminiaturized reflection in the reflected spheres, and micromicrominiaturized in the reflection of reflection of other spheres. These will look like noise to your eye, but that's what the real scene would look like, also.
-Greg
···
From: Yun-Xian Ho <[email protected]>
Date: May 22, 2006 4:50:51 AM PDT
Hi All,
I have been having problems rendering a glossy bumpy surface composed of intersecting ellipsoids illuminated under a rectangular light source. The image appears to contain some random point source reflections on the surface in addition to the direct reflection of the area light.
To view the rendered image, see: http://homepages.nyu.edu/~yxh201/bumpysurftest.jpg.
The bumpy surface is made of the following material:
void plastic gray_plastic
0
5 .2 .2 .2 .1482 0
and a 30x24 flat rectangular light source is defined as:
void light bright
0
3 25 25 25
I use the following parameters to render the scene:
-ab 2 -aa .08 -ad 1024 -as 512 -av .2 .2 .2 -sj 1 -st .01 -dj 1 -ds .05
Any suggestions to clean up the "noise" in the image? Much thanks...
--xian
Thanks for the speedy and helpful responses, Jack and Greg. It's good to know that there is nothing necessarily wrong with my code, just my perception. 
This also suggests that I should probably not make these surfaces "shiny." In response to Jack's P.S., the geometry is designed to investigate gloss and the perception of bumpiness, where bumpiness is defined as the variance of bump heights (ellipsoid depths). I was inspired by a variety of skin imperfections...and clusters of shiny raspberries. If course, if anyone has any better suggestions of modeling "macro-bumpiness," I'd be happy to hear them.
--xian
Gregory J. Ward wrote:
···
Hi Xian,
Adding to Jack's comments, I think you will see what appears as noise no matter what you do. The minification that happens on multiple reflections makes your light source into a dot. In other words, in the reflection of one sphere you see more spheres. The miniaturized image of the light source becomes a microminiaturized reflection in the reflected spheres, and micromicrominiaturized in the reflection of reflection of other spheres. These will look like noise to your eye, but that's what the real scene would look like, also.
-Greg
From: Yun-Xian Ho <[email protected]>
Date: May 22, 2006 4:50:51 AM PDT
Hi All,
I have been having problems rendering a glossy bumpy surface composed of intersecting ellipsoids illuminated under a rectangular light source. The image appears to contain some random point source reflections on the surface in addition to the direct reflection of the area light.
To view the rendered image, see: http://homepages.nyu.edu/~yxh201/ bumpysurftest.jpg.
The bumpy surface is made of the following material:
void plastic gray_plastic
0
5 .2 .2 .2 .1482 0
and a 30x24 flat rectangular light source is defined as:
void light bright
0
3 25 25 25
I use the following parameters to render the scene:
-ab 2 -aa .08 -ad 1024 -as 512 -av .2 .2 .2 -sj 1 -st .01 -dj 1 - ds .05
Any suggestions to clean up the "noise" in the image? Much thanks...
--xian
This also suggests that I should probably not make these surfaces "shiny." In response to Jack's P.S., the geometry is designed to investigate gloss and the perception of bumpiness, where bumpiness is defined as the variance of bump heights (ellipsoid depths). I was inspired by a variety of skin imperfections...and clusters of shiny raspberries. If course, if anyone has any better suggestions of modeling "macro-bumpiness," I'd be happy to hear them.