The corrosion shader is a very versatile shader that can be used for adding quick bumps and other appearance control for surfaces.
We´ll start with a simple golden sphere lit by a spotlight with a ground plane.
We´ll apply a new corrosion shader to it, without changing the shader preset values or changing the mapping. What we get will be something like the image below.
What is this? Some parts are bumpy, some are not, and there are no holes in the sphere.
The parameters that we can control in a corrosion shader are:
- Hole Area: Controls the percentage of the area that looks perforated. In the image above none of the area looks perforated. We´ll see why soon.
- Resistant Area: This resistant area has a different bump amplitude than the “normal” corroded area.
- Bump Amplitude: The general amplitude of the corrosion bump.
- Resistant Bump: The bump amplitude of the resistant areas.
- Seed: This is a base number that causes that different shaders with different numbers behave differently.
Hole Area
The hole area shows a hole if the corrosion shader is the only shader applied to the object, or the underlying texture if the corrosion shader sits on top of another texture, unless the underlying texture’s Mix is set to Inherit.
Compare the render above with the one below. What appeared like gold without bumps now appears as a hole.
Corrosion shader, 40% hole, underlying texture mix set to Inherit
Same as above, Hole Area set to 75%
Resistant Area
The resistant area slider controls the percentage of the surface that is resistant to the corrosion, and thus has a lower bump amplitude.
Left to right: 10% Resistant Area, 50% Resistant Area, 90% Resistant Area
Bump Amplitude and Resistant Bump are bump amplitudes similarto the one in surface textures.
In the render below, the bump amplitudes in the left sphere are 20 and 10. In the sphere in the middle,the values are 5 and 2. In the sphere on the right, the values are 1 and 0.5.
Different bump amplitudes
Seed
Changing this number will get the shader applied in different ways to the object. In the image below, the Seed numbers are, left to right: 1,2,3.
Different seed values
In the next installment, we´ll cover mapping strategies to take full advantage of the corrosion shader.
