3D Drawing with AutoCAD - Section 8

CHAPTER 40: MODELIZED

We call Modeling the process of creating photorealistic images from 3D models, although it is more frequently known by the anglicism "rendering". This process fundamentally involves three phases: a) Associate the different solids, surfaces and meshes of the model to representations of materials (wood, metal, plastic, concrete, glass, etc.); b) Create the general environment in which the model is located: lights, background, fog, shadows, etc. and; c) Choose the type of rendering, the quality of the image and the type of output to be produced.
It is easy to say, but this is a CAD area that, while not complicated to understand, requires a lot of experience to achieve good results with few attempts. That is, it is very likely that many hours of trial and error will be spent in order to learn the best methods for correct assignment of materials, the application of environments and lights and the generation of satisfactory outputs.
Each phase, in turn, involves the establishment of many parameters, whose variation, however small, always affects the final result. For example, we can determine that a rectangular prism is made of glass, which will force it to have some degree of reflection and transparency, so it will have to modify those parameters to achieve a good effect. In turn, the walls, to be seen as such, must have the roughness of the cement. The same could be said of the metal parts of an automobile or the plastic parts of an appliance. In addition, it is always necessary to apply lights correctly, considering the ambient light, intensity and distance to which the light source is located. If it is the light of a bulb, it must be correctly oriented so that the effect of shadows is effective. In the case of architectural projects, the correct location of sunlight, considering the date and time, is essential to know the appearance of a building that is not yet built.
Thus, rendering or rendering can be an arduous but truly rewarding task. Many architectural firms devote much of their efforts to modeling their projects before presenting them to their clients, and there are even offices devoted exclusively to generating the outsourced modeling of third parties, turning this process into a business area in and of itself, Even in an art.

Let's look at the process of Autocad Modeling.

40.1 Materiales

40.1.1 Assignment of materials

One of the first steps we have to take to create a good photorealistic effect of an 3D model is to assign the materials to be represented in each object. If we draw a house, some parts will probably represent concrete, other bricks, and a few more wood. In somewhat more abstract models it may be desirable to represent other materials or textures for which it may be necessary to modify the parameters of existing materials. By default, Autocad includes around 700 materials and 1000 textures ready to be assigned to the objects of a model.
It should be remembered that the graphical window of Autocad will show or not a basic simulation of the materials depending on the visual style used. Obviously, the recommended style for these cases is called Realistic, although that does not imply that the view of the graphic window is already the modeling.
Once the correct visual style is established, the access, use and personalization of these materials is the same in all cases through, first, the Material Explorer, which is in the Materials section of the Render tab.
The Material Explorer allows us to know the different materials and the categories in which they are organized. In it you will find the library of materials of Autodesk, these materials can not be edited, for it is necessary, or assign them to the current drawing, or create customized libraries of materials that you can then call from other drawings for their use. If you do not intend to make any changes to the materials, then you can assign them to your model directly from the Autodesk library and omit the creation of your own library.

In fact, before assigning a material to an 3D object, it is important to first activate the materials and textures in the model. This is as simple as pressing the button of the same name in the Materials section. The second thing to consider is that the correct application of textures in an object depends on its shape. It is not the same to assign a material to a sphere as to a cube. If an object is curved, then the appearance of its texture must follow, and show, that curvature. For the simulation of a material on an 3D object to be effective, the map of the distribution of the texture on the surface of the model must be adequate. The program requires the texture map parameter to be applied to each object and for that the next button in that section is used.

In any case, as you have already seen, the assignment of materials to objects is very simple, just select the material, either from the Autodesk library, from the ones incorporated into the drawing or from your own libraries and then point out the desired object. It is also possible to select an object and then click on the material.
Another possible option is to assign a material to only one side of an object. For this we can use sub-object filters or press CTRL to select a face, then click on the material.

A more organized method for assigning materials is through the use of layers, although with this method we can only assign materials that have previously been assigned to the current drawing, as we saw in an earlier video. To do this we use the Link materials by layer button of the section that we are studying, which opens a dialog where we simply have to link the different layers to the selected materials. Thus, a well-organized layered model will greatly simplify the assignment of materials.