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When you ask Blender to make a render of an image, it uses what's called the shaders to compute what every surface should look like. So let's go ahead and press F12, for those of you on the PC, or for those of you on the Mac, if F12 is remapped to a widget, then come over here to the Scene Context and click the Render button and that generates a render and places the resulting image over here in this UV/Image Editor. And in this sample setup we have the sphere, which is lit by two lamps.
A soft Hemi lamp which is shining on the globe here which you can kind of see through this white color and then a very bright piercing light above it which is an omnidirectional light. As you can see, the surface of the sphere goes from a purple color to this white color here and this white color and purple color is set over here in your diffuse and your specular colors in the Material panel, under the Shading Material context. Now the amount of the color and where this specular starts and where it ends is all setup in the Shaders panel, which is the main purpose of this tutorial.
We have five different shaders to choose from and each of these is usually generated by a different guy or a different person that was working on this math to come up with different algorithm for computing the surface and we are going to run through them. For the Lambert Shader, which is the normal shader that's used, the one control you have is the amount of reflection of the color that occurs when the object is hit by light. So a lesser reflection means that the sphere up here is darker or deeper or richer kind of a color.
The Specularity refers to the amount of specular color that is reflected as the light hits a sphere. So now, a little bit of light hitting the sphere results in a lot of specular color being blended in. The Hardness refers to the diameter of this specular reflection. A larger number increases the hardness, which actually diminishes the size of that spherical reflection. Usually, things have very little specularity and very little hardness.
Usually things are like cardboard or soundproofing or paper. They really spread the light over a very broad area and if all of your stuff is looking like plastic, it's because you have the specularity and the hardness up way too high. Also it could be depend on the kind of lamp you are using too. This Hemi lamp provides a nice base, even amount of lighting. The omnidirectional is very hard point source of light. The other shader is the Oren-Nayar shader. That algorithm is designed to reflect some roughness in the surface.
At the microscopic level, the lamplight is diffused. So I'm going to go ahead and change the lamp, to be a Spot lamp to better illustrate this point. Now even though the Spot lamp is shining directly on the sphere, you are not getting a very hard, crisp, specular reflection. You are instead getting a very rough surface as though this was made out of rough sandpaper. The Toon shader goes with the toon specular shader and we are just going to go ahead and jump into the different specular shader here.
And this Toon shader was developed to enable Blender to provide cartoon style renderings from 3D objects that look as though they were cel-shaded. The Toon shader has a couple of different other controls. One of which is how much color is reflected, which is common pretty much throughout of all of the different shaders. The size of the diffuse area and the smoothness of the transition from the diffuse to the specular. So just making those few changes, you can see that the specular and the diffuse settings and appearance is very different.
By increasing the Specularity, increasing the Smoothness, we are now getting this very odd kind of color. Most cel-shading uses a very sharp line between the diffuse and specular and so you get this kind of an effect. This provides a smaller smoothness setting on the diffuse. It says that there is less of a shading gradient among the different areas of the sphere that are getting the different light amounts.
The Fresnel effect is a pretty wild effect. I'll go ahead and switch this back to the CookTorrance. The Fresnel effect is used a lot on glass materials and that provides a very neat, magnifying kind of effect. As the light hits the surface, it's spread out and reflected back. The Minnaert shader is very good for metal type of surfaces. If you want something to look like it's a painted metal, then you can use the Minnaert. The Tangent Vector, sort of flips the effect so that instead of getting a normal shading, you get a tangent shading and the closest way I can explain this is Christmas balls that are wrapped with very fine like metal string when they are hung on the tree, you get this kind of banding kind of effect going on.
Shadows, we have talked about, is that this material can have shadows cast on to it and if it does receive shadows from a transparent object, then the coloring and the effect on this object from that shadow is based on the Alpha channel. We can have this object render its shadow on a material as an Alpha value and that helps us when we are blending shadows together. Cubic uses a faster fall-off, so if we are using a Lambert shader, and no Tangent, then this Cubic helps ease this fall-off that occurs when one light source blends in with another one.
Down here under Translucency if we increase the Translucency and we make the material slightly transparent, then as the light goes through the front part of the material, it's going to hit the backside of the material and then reflect back out through the front side of the material. So the Translucency helps simulate what happens with a real globe. Let's say as light enters into the globe, it gets bounced around on the backside. Here you can see this purple and then comes back out though the front side for us to see.
Ambient light we have talked about before is the amount that this material as effected by the ambient light and Emitting is used with radiosity to say that this almost is lit up. So now we have a glass globe that is lit and actually cast soft light out into the rest of the environment. I'm going to turn this down. And lastly but not least, the LBias helps with the shadow buffer lamps and makes them darker. A lot of times a shadow buffer lamp will cast kind of a general gray kind of a shadow and not really a crisp dark shadow and LBias helps define this shadow better from a shadow buffer lamp.
So that's real brief overview of the five different kinds of diffuse shaders, a little bit on the specular shaders. The Phong shader is used for like the surface of pitches and fuzzy things. Faces are good for Phong shading and things like that. Wardiso is a specular shader that also is good for metal as well. So play with the different shaders and experiment to see what kind of effect they give under the various different kind of lighting conditions so that you come up with a great combination that gives the shading across the surface of the material that you want to use.
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