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Author Topic: Phong shading and material question  (Read 2280 times)

Metatron

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Phong shading and material question
« on: September 22, 2008, 11:21:08 am »

1. Does the ART renderer apply Phong Shading or Gouraud Shading to the objects it renders?
Sometimes the silhouette of a sphere doesn't look smooth. I'm not sure whether this is because I didn't use enough subdivisions, or whether the smoothing angle (I used default: 45) is responsible for this. Or perhaps I need to manipulate the edge properties of the sphere's edges?
What can I do in order to render a 'perfectly' smoothed Sphere?

2. I tried to find a material that resembles Bronze as close as possible.
I did my best to setup a basic 3-point lighting plus I set global illumination to 0.75 and ambient illumination to 0.1.

Here are the values that worked fine together with this lighting setup, when I applied the material to a Cylinder:

Ambient (r:56, g:33, b:7, intens: 0.1)
Diffuse (r:141, g:91, b:6, intens: 0.95)
Specular (r:215,g:148,b:88, intens: 17*) (*here is a problem described below)
Emission (default)
Rough (10)
Trans (1)
Brilliance (2.5)
(**) - question

(*)
Overall I was satisfied with the bronze cylinder, but here is (*)-problem:
I couldn't add a very weak reflection to this material (specular reflection), due to the very high intensity of the specular color (but this was necessary in order to achieve the broad specular highlight that I was looking for), the reflection of surrounding objects (or the ground plane) is far too strong. Any tipps on how I can make a broad specular hightlight while at the same time the reflections should be very weak could help me a lot. Thanks in advance.

(**)
When I applied the same material, which worked fine with the Cylinder, to a Sphere, the material didn't resemble bronze at all, the Highlights were way too huge, and I had to reduce Specular Intensity to 0.95, although the Metallic Look was better then, now the overall color didn't match anymore.
Is this a common feature of materials (in general), that they can work well on Cylinder and at the same time don't work at all with a Sphere? Does the realistic look of a material depend on the geometry of the object?

Is there a way to add specularity maps or bump maps together with the same material?

Big Thanks for making this great piece of software.
Big Thanks for Tipps on how to make Bronze Material, that does work with any geometry.

Here are two pictures (Title: The search for a good Bronze Material):

Cylinder (overall I'm satisfied with this. Here the specular intensity is 17)


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Sphere (messed up, I reduced the specular intensity to 0.95 here.
 The sphere doesn't look smooth, when I look closely. -> Is there a way to tell ART it should render using Phong Shading instead of Gouraud?)


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BUT: There is also a chance I messed up the light setup (One very strong directional light as key, a local fill light and a local back light (both very far away and thus weak).

Is there any in-depth tutorial about using materials and lighting in Anim8or?
« Last Edit: September 22, 2008, 11:40:23 am by Metatron »
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hihosilver

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Re: Phong shading and material question
« Reply #1 on: September 22, 2008, 05:21:48 pm »

1.  The silhouette will always depend on the actual geometry.  This is why when people create game models nowadays, they almost only focus on the silhouette, the rest of the detailing can be done with things such as normal maps.  But when rendering, yes, the silhouette will always be defined by the actual geometry (unless you're using a transparency map.)  So, you'd either want to create a new sphere with more divisions or convert the current sphere to a subdivision object (Build>Convert to subdivided) where you can change the subdivision level at your will.

2.  (*)  I'd advise using the class>glossyreflector attribute.  You can read about it here, but basically this attribute depends on the rough value instead of the specular value.  Though, you will end up with a grainier reflection unless you use a higher number of samples for AA.

(**)  The material will not always look the same on models of different geometry.  Here's my explanation for what's happening:
The cylinder is very skinny, therefore, when you set the rough value to a lower level, it still wont spread out as much as the sphere since the sphere has a slower curve, therefore more light reflects off of it.
Basically, the specular value should not change how broad the highlights are, that's what the 'rough' value does.  Specular should only change the highlights intensity.
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VBSmiles

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Re: Phong shading and material question
« Reply #2 on: September 23, 2008, 05:47:36 am »

I've been successful with using specular - reflection.


Not sure how I can send an .an8 and cant add the new attributes via script ( least that I know of )

Basicly just tweeked the metals avalible around the net. I used to have a sweet rainbow of metals, but don't think it's around any more.
« Last Edit: September 23, 2008, 05:51:13 am by VBSmiles »
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hihosilver

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Re: Phong shading and material question
« Reply #3 on: September 23, 2008, 06:06:23 am »

Check out this old thread of mine.  You may find the materials for download useful.  You can simply alter the colors of them, and play with color settings and such.
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Metatron

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Re: Phong shading and material question
« Reply #4 on: September 23, 2008, 11:25:46 am »

Thanks a lot for your tipps, I've learned a lot from them. :)
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Steve

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Re: Phong shading and material question
« Reply #5 on: September 24, 2008, 06:36:31 am »

Metatron,

Anim8or uses Phong shading fro ART and for both the scan line renderer.  Gouraud would have much more noticable triangular artifacts on your Sphere.

For a shiny reflections see the "Specular Kinds" scene in the attached project.  You can look at the materials and their attributes in the Object editor in the File materials window.

Set the number of Latitude and Longitude divisions to a higher number (16,32 and 32/32 work well ) and your sphere will be smoother.

VBSmiles, you can attach .an8 files to posts.

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