[ISL] I board failed to do polka dots

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Jay-ko
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[ISL] I board failed to do polka dots

Post by Jay-ko » Tue Jun 14, 2016 11:26 am

Hello there,

I really would like to do something more "ISL-ist" with this material.
http://www.indigorenderer.com/materials/materials/1513

But this way of "think" at the contrary of that I know, and my poor knowledge in the ISL basics cause me a lot of waste of time and frustrations.

Because I understand that is simple example, and I feel like an idiot when I don't succed to re-do this simple exemple like I want, and this so easy to do that in bitmap with Substance or Photoshop...

Could you please help my to place me on the way to understand this example:
http://www.indigorenderer.com/materials/materials/154

Code: Select all

<shader>
                        <![CDATA[def dist(vec2 a, vec2 b) real : length(b - a)
def dist(vec3 a, vec3 b) real : length(b - a)

def eval() real :
  if(
    dist(
      vec2(
        fract(doti(getTexCoords(0)) * 10.0),
        fract(dotj(getTexCoords(0)) * 10.0)
      ),
      vec2(0.5, 0.5)
    ) > 0.25,
    0.0,
    1.0
  )]]>
</shader>
First at all, I wish try step by steps.
I can copy this blend map shader
and then copy/paste it in the bump with a larger size of the dots to obtain a fake "thickness effect".

How can I change the size of the dots?
Attachments
polkadot.png
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CTZn
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Re: [ISL] I board failed to do polka dots

Post by CTZn » Tue Jun 14, 2016 2:12 pm

In the

Code: Select all

     dist(
      vec2(a),
      vec2(b)
    ) > 0.25
bit, it's the 0.25 that you want to tweak. It's the limit of the dot, from the distance from the center vec2(b) to the actual coordinates being sampled in UV space vec2(a).
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Jay-ko
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Re: [ISL] I board failed to do polka dots

Post by Jay-ko » Fri Jun 17, 2016 10:40 am

OK thank you!

Next step, understand why I cannot use this piece of code directly in the bump channel, or why the "b" value seems have no effect.
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Zom-B
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Re: [ISL] I board failed to do polka dots

Post by Zom-B » Fri Jun 17, 2016 5:44 pm

Jay-ko wrote:Next step, understand why I cannot use this piece of code directly in the bump channel, or why the "b" value seems have no effect.
Your shader actually "overides" this b value, you need tweak the strength inside the shader, but I have no idea where -.-'
(I only know this from using ISL noise in bump etc.)
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galinette
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Re: [ISL] I board failed to do polka dots

Post by galinette » Fri Jun 17, 2016 6:48 pm

Also, in order for bump to work, you need a smooth transition between "high" values and "values". A brutal, vertical transition does not work well with bump, because bump is actually based on slope, not height.
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CTZn
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Re: [ISL] I board failed to do polka dots

Post by CTZn » Sat Jun 18, 2016 6:10 am

Galinette is of course plain correct; this specificity of bump mapping has raised countless, pointless arguments on the effectiveness of bump mapping based on texture resolution.

Bump mapping is like a radar scan from above; a perfect cliff will be invisible, the terrain seemingly flat.
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