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What is? 3D modeling ？ High and low middle mold 、 Normal map 、 What are low mode topologies ？ - Bili, Bili

[ translation ] Displacement mapping 、 The difference between bump map and normal map - You know

Difference between Displacement, Bump and Normal Maps | Pluralsight

What is? 3D modeling ？ Is the modeler modeling out of thin air based on imagination ？ Modeling is not complicated ？ What are the workflow ？
One 、 Modeling process （Workflow）

         Modeling is mainly divided into two parts: Modeling and mapping , The modeling process can be simply understood as “ Plastic bone ”, The process of mapping is understood as “ beauty ”.

1.1 modeling （Modeling） It is divided into role modeling and scene modeling , The modeler builds the basic model according to the original drawing , This is an important part of the whole game art design .
         There are a lot of software that modelers have to learn to use , The modeling software commonly used in the game industry is 3ds Max、Maya、ZBrush、Blender etc. . Different industries and projects focus on different software , Therefore, it often takes quite a long time for newcomers to enter the industry by themselves, and they are not professional and comprehensive enough , It is easy to generalize or fall into a dead corner .

1.2 Mapping （Texturing）

         Just use Photoshop、Substance Painter、3DCoat And other software to make a material plan , Used to cover the surface of the model .
         What color are the scene props ？ Is it metal or wood , Is it new or old ？ Is the character young or old ？ Is the skin smooth and delicate or full of freckles and wrinkles ？······ The appearance of these models is determined by the map .

         It is worth noting that ： Modelers usually do not work directly on three-dimensional models “ Dress up ”, Instead, the three-dimensional model is expanded into a two-dimensional plane and then mapped 、 Add details, etc , This is called. “UV Split ” or “ exhibition UV”, Commonly used Unfold3D、UVlayout And the built-in system of modeling software .
         We can think of it as making a gift box , First lay the box flat , After finishing the dress up of the external packaging , Then fold it into the desired shape . Of course, this “ packing box ” There are many production steps , Therefore, it usually leads to several concepts in the following .

Two 、 in / high / Low model （Mid/High/Low Poly）

Usually an object is composed of several points, lines and surfaces , A polygon can be identified as one side . It is customary to call the number of polygons in a 3D model as the number of faces , That is, what is the number of faces of the model .

         According to the habits of the modeler , Generally, first make a preliminary shape from the middle mold . No protection line is built in the medium formwork , Used for later cutting low die and engraving high die , It belongs to the transition product between high and low modes ; In order to express the structural plane, the number of high modulus will be too many , To generate normals 、AO Maps and displacement maps ; Low mode is generally only large , Details depend on mapping . But this does not mean that a large number of faces must be a high model , And the modeling methods of high and low models are also different . With the development of technology , It is not appropriate to define the high and low modulus simply by the number of faces . The high performance of high mode often brings huge operation burden to the equipment . Film and television advertising pursues the fidelity and fineness of the model , Usually pre rendered , So use more high models ; And the game needs to be rendered in real time , So hand games and ordinary picture quality games usually use low models . That's why 《 Game for Peace 》 Even if the face pinching function is used in , After entering the game, you still see the default face . Empathy , Although the medium mold will be transformed into the high mold with the highest precision after clamping or engraving , But it will also cause the mapping to run slower , Therefore, you need to assign a map to the low mode .

3、 ... and 、 Low mode topology （Topology）

         In order to make the low mold have the concave convex details of the high mold , So it came into being “ Low mode topology ” The concept of .
        “ Topology ” It is a subject that studies some properties of geometry or space that can remain unchanged after changing shape continuously , It only considers the position relationship between objects without considering their shape and size . and “ Low mode topology ” It refers to reconstructing a low mode according to the wiring principle of high mode , To make the low die show more details with a lower number of faces , The common software is ZBrush、Maya Its own topology or

Four 、 Bake normal map （Bake Normal Maps）

         After topological low mode, we will go to the above mentioned “ exhibition UV” do “ packing ” The link of mapping .
         A normal is a dashed line that is always perpendicular to a plane , Is used to describe the direction of the surface . Any point on the plane of an object , The direction perpendicular to the plane is the normal direction . To avoid putting “ Packaging pattern ” In the wrong direction , When baking map normals, save the normal direction of high mode to the surface of low mode in the form of pixels , In this way, the low mode pasted with normal map can have the light shadow bump of high mode , It looks like a high model .

5、 ... and 、 Engine render （Rendering in the Engine）

Finish mapping the low mode 、 Material drawing （Texturing） After the improvement of and details , You can render and export the model in the game engine , There are eight common rendering engines 、UNREAL、UNITY 3D etc. .

         The workflow breakdown of modeling includes ： The middle mold starts to form - High model fine carving - Low mode topology -UV Split - Bake normal map - Paint materials - Engine rendering, etc , It's all the workflow that the modeler should master .

Displacement mapping 、 The difference between bump map and normal map

Original English address ：Difference between Displacement, Bump and Normal Maps | Pluralsight

         Many maps or 3D Artists in the field first encountered bump mapping (Bump map), Normal map (Normal map) And displacement mapping (Displacement map) When you wait for the concept, you will feel confused .“ They seem to do the same thing , Isn't it ？” The answer to this question lies in that “ almost ”. All three maps are used to create some effects , It looks like adding resolution or more to the surface of the geometry details . And these details Some are true, some are false .

One 、 Bump map (Bump Maps)

         Bump mapping uses computer graphics in 3D The surface of the model creates the illusion of uneven texture . We use grayscale (Grayscale) Figure and simple light and shadow techniques artificially create this texture on the surface of the object , Rather than really buckle out one bulge and crack on its surface .

         In today's view , Bump mapping is actually an old technology . The first thing you need to know is that the details produced by bump mapping are fake . Bump mapping does not add extra resolution to the model . Generally speaking , Bump mapping is only 8 position (8-bit) Grayscale image of color . That is to say, it only has 256 There are different shades of gray . The value in bump map tells 3D software two things ： Concave or convex . When the duty is close to 50% Gray scale , There is little detail change on the surface of the object . When the gray value becomes bright ( white ), The surface details are presented as bulge , When the gray value darkens ( black ), The surface details are presented as Concave . It's great to use bump mapping to achieve small details of the model . such as , Pores and wrinkles on the skin . They can be used like Photoshop And other two-dimensional software can be edited relatively easily . The problem with bump mapping is , If the camera is at the wrong angle , Bump mapping will be easy to wear . Because after all, the details are fake , It doesn't increase the real resolution . The outline of the geometry (silhouette) Will not be affected by the bump map on it .

Two 、 Normal map (Normal Maps)

         The normal map can be considered as a newer and better bump map . Just like bump mapping , For normal mapping , First of all, you need to know , Its details are also fake . No additional resolution is added to the geometry . Last , Although normal mapping also creates an illusion of detail on the surface of the model , But its implementation is different from bump mapping . As we know , Bump maps use grayscale values to provide bump information . The normal map uses RGB The information tells 3D Every polygon in the software (Polygon) The exact orientation of the surface normal . The orientation of these surface normals ( Sometimes referred to as normal ), Will tell 3D How does the software color polygons . When learning normal mapping , You should know that there are two types . stay 2D The two types in space look completely different . The most commonly used one is called tangent space normal mapping (Tangent Space Normal Map), It shows a mixture of blue and purple .

3、 ... and 、 Displacement mapping (Displacement Maps)

         If you need to add extra details to your low resolution model , So displacement mapping is the king . Those maps will be replaced at the physical level ( As its name suggests ) The mesh they act on . Use displacement mapping , In order to be able to create details , Mesh models are generally subdivided , In this way, the real topology can be created . The advantage of displacement mapping is , It can be baked from high-resolution models , You can also draw it manually . Just like bump mapping , Displacement mapping is also by 8-bit Gray value composition .

Four 、 Use multiple maps

         Sometimes you can use a combination of bump maps on the same resource / Normal map （ A choice ） Displacement map . The best strategy is to use displacement mapping to achieve those large deformations , Use normal or bump mapping to achieve those small details . No matter what kind of map you use , Knowing their principles and their strengths and weaknesses will make it easier for you to make judgments . The ultimate criterion is that the map you choose should best meet your needs .