General information about bump maps
The settings on this page enable you to simulate bumps.
Figure 2 shows an even surface viewed from the side.
The surface has a uniform brightness. However, if you use a bump map for the same surface, Cinema 4D interprets the brightness values of the picture as height values for the surface (Figure 3).
These height values are converted into a profile, whose height affects the inclination of the normal vectors. Although the surface is actually smooth, through the change in the normal vectors an apparently three-dimensional surface with a bump-like structure is created at render time.
Various ways of creating structure
There are basically four ways in which structure can be added to a surface for rendering.
The following methods are available, listed in ascending order with regard to render time/quality (whereby the first three use render tricks and the subpolygon displacement actually raises/sinks the surface, thus offering the most realistic-looking results):
What they all have in common is that they all evaluate a texture’s grayscale valuse to define height and depth. So when should which method be used?
Generally speaking, the following rule of thumb can be used:
However, you should always experiment to achieve the best result for your scene. As always, you have to find the right compromise between render quality and render time.
The strength of the bumps. The higher the value, the rougher the surface. If you move the slider to the left, you can choose negative values to reverse the effect of the bump map — bright pixels then cause the material surface to indent while darker pixels elevate the height of the surface.
Parallax mapping is a new feature included with Cinema 4D R18. It provides approximately the same quality as subpolygon displacements but without having to subdivide the object internally. This reduces render times dramatically. Internally, Parallax mapping "bends" the UV coordinates to feign elevation on a surface. The color texture is distorted in a manner that makes its perspective distortion appear to be correct (e.g., the black stripes at the right the image above).
However, since it does not alter geometry, some restrictions have to be accounted for when using Parallax mapping:
Imagine Strength and Parallax Offset as separate sliders: Strength defines the shading based on the bump effect and Prallax Offset calculates the texture distortion. The best results can be achieved when both settings are defined, i.e., bump and Parallax mapping are implemented simultaneously.
Use this setting to define the strength of the effect, i.e., the degree with which the UV coordinates should be moved to feign an elevated structure. Make sure to adjust the Strength setting (it most often has to be increased; it must also be not equal to 0 in order to calculate a parallax effect) to produce convincing results.
Negative values can also be used to reverse the effect: raised regions will be sunken and vice-versa.
If the value is set to 0, no Parallax Mapping will take place. Bump mapping will take place instead.
Normally, these values do not have to be modified. However, if Parallax Offset were set very high, artifacts, as shown at the left of the image above, would appear. To offset this, increase the Parallax Samples value. Higher values will result in correspondingly longer render times.
You can strengthen the MIP/SAT mapping effect when using bump mapping by enabling MIP Falloff. The bump mapping is then reduced the further the surface is from the camera.
Here an image texture or a 2D shader can be defined. Refer to the Textures chapter for details.
You must use a texture with this channel. It is only from the grayscales in this image that the bump map (a height or relief map) is calculated.
It is very important to have a fitting Shader in the Bump channel (in this example, logically, a Water Shader) in order to make an effect look better. In the example above, the large waves are created with the help of Cloth (Edges are fixed and Wind was both applied to the Cloth tag itself and as a separate Wind Object). Since such smooth waves can only be reproduced in a laboratory setting, the Water Shader (insert center) in the Bump channel is used to create the typical "mini waves", which alleviates you from modeling them.