Dissertation fragments: part 4 – Material analysis: Common Material Attributes
In this part I will explain the most used attributes that shaders have one by one. This following attribute groups will be analysed: Common Material Attributes, Specular Shading, Special Effects, Raytrace Options and mental ray.
Common Material Attributes.
Common Material Attributes is where you can control the basic attributes of your shader:
– Colour: Controls what is the main colour of the object. (Fig1)
– Transparency: Controls how much transparent is the object. (Fig2)
– Ambient colour: When there is an ambient light in the scene you can control which colour is seen in the faces that it is lighting. (Fig3)
– Incandescence: Add colour uniformly to the surface. To create a simplistic bulb effect, you can use the maximum incandescence and it will seem as if the object made light, because it hasn’t shadows. (Fig4)
– Bump Mapping: Give to the object an optical 3D texture. The object hasn’t true texture but makes the light act on the object as if has. It’s the more simplistic way to represent roughness in textures. (Fig5)
– Diffuse: Determines the brightness of the material, how much light is reflected from its surface. (Fig6)
– Translucence: Controls if the material can let the light pass through but being opaque. Translucence tends to be applied to thin objects that are opaque but too slim to absorb all light that pass through. (Fig7)
– Translucence Depth: Controls how long goes the light trough. On a dense material (like stone) translucence depth will be lower than a material like paper or skin even being the same size. (Fig8)
– Translucence focus: Controls the directionally of the scattered light.
– Fig1: There are three objects with three different colour blinn shaders: Cyan, yellow and magenta.
– Fig2: In this case, there are three different blinn shaders, with three different levels of transparency.
– Fig3: Three pink objects with different ambient colour attributes. The complex shape and the cube have a blue ambient colour; the sphere’s ambient colour is red.
– Fig4: There are three blinn shaders with different incandescence level. On the sphere we can see that has any shadow. It’s because the incandescence is 100% and it is as the sphere produced light.
– Fig5: In this case, the sphere has a grid texture to reproduce the roughness effect on the surface using a bump map. Tue cube has a browonian texture and the complex shape a wood one.
– Fig6: In this picture we can see three lambert materials with three different diffuse levels. In the sphere and the cube we can see that ambient light doesn’t work with them. It’s because diffuse level is 0 in the sphere case and very low in the cube. It means that ambient light doesn’t bounces on their surface.
– Fig7: In this figure there are three equal objects. The only difference between them is the translucence attribute. In the closer one that we can see that light can’t pass through but in the farthest one it can. Respectively they have a 0% and a 100% of translucence.
– Fig8: There are three equal objects. The only difference between them is the translucence depth attribute. In the closer one light can’t pass through the front face, in the middle shape there is some light that can pass through the front face but only a little can pass through the whole object. In the farthest one all ray light can pass through the entire object.
– Fig9: In this picture there are three equal objects. Anew the only difference between them is only one parameter: Translucence focus. In the closer shape case all the light rays pass in only one way and they have the power to pass through the object. In the farthest shape case light rays doesn’t pass in a directional way through the object.