\n| \n ![\"MlLkShflFE](\"\/img\/825\/image092.jpg\" "\\"MlLkShflFE") <\/p>\n<\/td>\n<\/tr>\n<\/table>\n
<\/p>\n info, and even the vertex normal information. Lets take a look at the SMs3dTriangle structure to see what solidifying the model entails:<\/p>\n \/\/———————————————————————-<\/p>\n \/\/- SMs3dTriangle \/\/- Triangle data structure struct SMs3dTriangle {<\/p>\n unsigned short m_usFlags; \/\/Editor flags<\/p>\n unsigned short m_usVertIndices[3]; \/\/Vertex indexes<\/p>\n CVector3 m_vNormals[3]; \/\/Vertex normals;<\/p>\n float m_fTexCoords[2][3]; \/\/Texture coordinates<\/p>\n unsigned char m_ucSmoothing; \/\/Smoothing group<\/p>\n unsigned char m_ucGroup; \/\/Group index<\/p>\n };<\/p>\n Well, that\u2019s not too bad. A total of six variables are used for every triangle in the MilkShape 3D model. The first, like the vertex struc\u00adture, is just an editor flag. Like vertices, a 0 means a regular, unselected face, a 1 means the face is selected, and a 2 means the face is hidden from view. Again, a face can be both selected and hidden if the value is 3. Notice that this flag variable here is two bytes, rather than just 1 like it is in the vertex structure.<\/p>\n Next come three more unsigned two-byte integers. These three inte\u00adgers are indexes into the array of vertices covered in the last section. The three vertices form a single triangle in the model. Using only the data covered so far, it is possible to create a solid model. However, it would be kind of boring with no textures or lighting.<\/p>\n Moving on down the line, you come to the vertex normals. A vertex normal is used for lighting. Each vertex normal is an average of all the normals of the faces its vertex shares. A face normal is perpendicular to the plane the face lies in; the vertex normal is the average of all the perpendicular vectors. A normal, whether it is a vertex or face normal, must be a unit vector with a magnitude of 1. These are stored in a CVector3 class. The CVector3 is made for vectors that consist of three floating-point variables that take up a total of 12 bytes. The main advan\u00adtage of using a Cvector3 for each normal rather than a simple array of floats is that the CVector3 class contains a myriad of functions. These functions make it a lot easier for you later on when you start animating the model. There are three normals\u2014one for each vertex index.<\/p>\n <\/p>\n \n\n| \n ![\"MlLkShflFE](\"\/img\/825\/image093.jpg\" "\\"MlLkShflFE") <\/p>\n<\/td>\n<\/tr>\n<\/table>\n
~\u0413\u0413^3-<\/p>\n Up next are the texture coordinates. The u and v coordinates are stored kind of strangely in MilkShape. There are a total of six floats\u2014 one pair of coordinates for each of the three vertices that make up the face. However, instead of being stored u1, v1, u2, v2, u3, v3 like you might expect, MilkShape stores all the us first, followed by all the v s.<\/p>\n This makes the order u1, u2, u3, v1, v2, and v3. If you do not remember this ordering, it will come back to bite you. I spent several hours debugging a program only to find I used the wrong texture coordi\u00adnates in the wrong places.<\/p>\n The last two variables deal with the group the face belongs to. These variables are not too important as you will see in the section coming up. The groups or meshes in the model take care of knowing which faces belong to each group.<\/p>\n Meshes<\/a><\/p>\nFor maximum flexibility, MilkShape 3D\u2019s triangles are grouped into meshes or groups. This allows different sections of the model to use different textures, materials, and even render only certain sections of the model. The mesh section of the file follows the triangle or face section, and like the other section is preceded by a two-byte integer telling how many meshes there are. Immediately following are the groups. There are 35 bytes of general information, followed by a num\u00adber of two-byte triangle indexes. The number of indexes is not constant; some groups may have more than others. To compensate for this dis\u00adcrepancy, you need to be able to dynamically allocate memory in each group to hold these indexes. Here is what the structure looks like.<\/p>\n \/\/————————————————————————————————<\/p>\n \/\/- SMs3dMesh<\/p>\n \/\/- Group of triangles in the ms3d file struct SMs3dMesh {<\/p>\n unsigned char m_ucFlags; \/\/Editor flags again<\/p>\n char m_cName[32]; \/\/Name of the mesh<\/p>\n unsigned short m_usNumTris;\/\/Number of triangles in the group<\/p>\n unsigned short * m_uspIndices; \/\/Triangle indexes<\/p>\n char m_cMaterial; \/\/Material index, -1 = no material<\/p>\n \/\/Let it clean up after itself like usual<\/p>\n \n\n| \n ![\"MlLkShflFE](\"\/img\/825\/image095.jpg\" "\\"MlLkShflFE") <\/p>\n
SMs3dMesh()<\/p>\n {<\/p>\n<\/td>\n<\/tr>\n<\/table>\n <\/p>\n m_uspIndices = 0;<\/p>\n }<\/p>\n ~SMs3dMesh()<\/p>\n {<\/p>\n if(m_uspIndices)<\/p>\n {<\/p>\n delete [] m_uspIndices; m_uspIndices = 0;<\/p>\n }<\/p>\n }<\/p>\n };<\/p>\n This structure takes a bit of care when being read in. The m_uspIndices variable is a pointer, meaning you just can\u2019t read in NumberOfMeshes * sizeof(SMs3dMesh). For each mesh, you must read the first 35 bytes that consist of some editor flags\u2014the same flags that the vertices and triangles use\u20140 for unselected, 1 for selected, and 2 for hidden. You must also read a 32-character mesh name and a two-byte integer that contains the number of triangles in the mesh. Using this last variable, you must allocate the memory for the triangles indexes.<\/p>\n The m_uspVariable is now ready to hold all of the two-byte integers necessary to show which triangles are used in the mesh. Each element of the array is an index into the array of triangles that was created and filled earlier in the load sequence.<\/p>\n Right after you read all the triangle indexes, there is a lone, single-byte variable that holds the index into the materials array (which you will be getting to in a second). The variable is signed, and a value of -1 means the mesh contains no material.<\/p>\n Last of all, as you can see, the structure takes care of deleting its own memory, meaning you do not have to worry about remembering to clear it when you are done using it. Deleting the array of meshes will automatically delete everything in them.<\/p>\n Materials<\/a><\/p>\nTo really make the model stand out and to add lots of customization, you can use materials. Materials control the way the renderer handles<\/p>\n <\/p>\n \n\n| \n ![\"MlLkShflFE](\"\/img\/825\/image097.jpg\" "\\"MlLkShflFE") <\/p>\n<\/td>\n<\/tr>\n<\/table>\n
~\u0413\u0413^3-<\/p>\n the texturing and lighting of the model. From textures, to color, to transparency, materials do it all.<\/p>\n The materials structure is fairly large and contains a lot of data, so bear with me here.<\/p>\n Remember to read in your two-byte variable that tells you how many materials there are before you jump into reading the material data.<\/p>\n Here is the material structure:<\/p>\n \/\/—————————————————————————-<\/p>\n \/\/- SMs3dMaterial<\/p>\n \/\/- Material information for the mesh struct SMs3dMaterial {<\/p>\n char m_cName[32]; \/\/Material name<\/p>\n float m_fAmbient[4]; \/\/Ambient values<\/p>\n float m_fDiffuse[4]; \/\/Diffuse values<\/p>\n float m_fSpecular[4]; \/\/Specular values<\/p>\n float m_fEmissive[4]; \/\/Emissive values<\/p>\n float m_fShininess; \/\/0 — 128<\/p>\n float m_fTransparency; \/\/0 — 1<\/p>\n char m_cMode; \/\/unused<\/p>\n char m_cTexture[128]; \/\/Texture map file<\/p>\n char m_cAlpha[128]; \/\/Alpha map file<\/p>\n CImage m_Texture;<\/p>\n };<\/p>\n You need to be careful when you start reading the data from the file. Instead of reading the whole group of materials in at once, you must loop and read them in one at a time. The reason for this is the very last variable in the structure, m_Texture. m_Texture is an image class that is used to store the texture for the material. This eliminates trying to sort out the textures later when you need to use them during the program. Note that this part of the structure is not actually contained within the file, making the actual size of the structure in the file 361 bytes. The CImage variable is a custom class that resides in the general basecode in the files (image. cpp and image. h). You can easily remove this variable and replace it with your own image-loading system.<\/p>\n The first variable in the structure is a 32-character array that holds the name of the material. This isn\u2019t all that important if you are just<\/p>\n \n\n| \n<\/td>\n<\/tr>\n<\/table>\n <\/p>\n making a loader, but it\u2019s nice to have when working with the model in MilkShape itself.<\/p>\n The next six variables contain the materials properties. These proper\u00adties determine the way the lighting of the scene will affect the model.<\/p>\n ■ The m_fAmbient and m_fDiffuse each store four floating-point values that represent the red, green, blue, and alpha (RGBA) values of a color. These colors help define the color of the material and determine how the polygons using this material will react to lighting in the scene.<\/p>\n ■ The next variable, m_fSpecular, also contains an RGBA color.<\/p>\n The specular material properties dictate the color of the specu\u00adlar highlights or \u201cshiny places\u201d on the mesh using the material.<\/p>\n ■ The last array of floats is the m_fEmissive set. This variable also contains four floats. The emissive property specifies how intense the material will emit light. The higher the values, the \u201cbrighter\u201d the material will be.<\/p>\n ■ The final material property is the shininess of the material. The m_fShininess variable contains a single float. This variable deter\u00admines just how shiny the specular highlights are. The lower the value, the darker and duller the highlights will be\u2014just the opposite as the value increases. Darker and duller highlights are used for materials such as wood and asphalt, whereas brighter, shinier highlights are best for shiny metal and artificial materials.<\/p>\n After all these material properties comes one more\u2014the transparency of the material, which is stored in m_fTransparency. Although the other material variables deal with color, transparency sets how opaque or \u201csee-through\u201d the mesh is. A value of 1 is completely opaque and a value of 0 is complitely transparent, or invisible. Because of the way OpenGL handles materials, the easiest way to handle this is to take this value and plug it into the last element of the diffuse property. This method creates a reasonably nice transparent mesh.<\/p>\n After these are all taken care of, you must skip a byte to compensate for a small, unused variable in the material information. This single byte variable m_ucMode is unused by the format for now. It is in there for use in later versions.<\/p>\n Then you get to the textures. The texture name is stored in a 128-byte string. After you acquire it, you can send it directly to the Load function<\/p>\n <\/p>\n \n\n| \n<\/td>\n<\/tr>\n<\/table>\n ~\u0413\u0413^~<\/p>\n of the CImage class included in the structure. This will retrieve the texture and take care of loading it so it is ready to use when you get to the rendering stage. The filename stored in the file can be passed directly to the CImage::Load() function or to your own texture-loading functions.<\/p>\n The last variable holds the filename of the alpha map. Due to the fact that I could find no information on this at the time this was written, the use of alpha maps on models is not currently supported. However, keep checking the Web site for the book and as soon as information is available I will update the code and the text and post it there.<\/p>\n Whew, that was a lot of information. However, you now have enough to render the model in what I call its \u201cinitial position\u201d. This is the posi\u00adtion before any animation is applied. In general, this position is opti\u00admized for ease of editing and probably does not appear in the actual animation sequence.<\/p>\n Figure 6.2 shows what the model would look like rendered.<\/p>\n \n\n| \n ![\"MlLkShflFE](\"\/img\/825\/image099.jpg\" "\\"MlLkShflFE") <\/p>\n
Figure 6.2 The model rendered in its initial position with textures, materials, and lighting enabled.<\/p>\n<\/td>\n<\/tr>\n<\/table>\n <\/p>\n <\/p>\n \n\n| \n<\/td>\n<\/tr>\n<\/table>\n <\/p>\n Pretty cool huh? Rendering the model isn\u2019t too hard. It basically involves drawing the meshes one by one, making sure to set the appropriate material and lighting properties beforehand. As usual, in order to make the code easier to read and convert to other languages and APIs, I use immediate mode calls that are pretty obvious in what they do.<\/p>\n The first thing that must be done is the material information. In OpenGL this can be done using the glMaterialf and glMaterialfv calls.<\/p>\n for(int x = 0; x < m_usNumMeshes; x++)<\/p>\n {<\/p>\n \/\/Set up materials if(m_pMeshes[x].m_cMaterial >= 0)<\/p>\n {<\/p>\n SMs3dMaterial * pCurMat = &m_pMaterials[m_pMeshes[x].m_cMaterial]; \/\/Set the alpha for transparency pCurMat->m_fDiffuse[3] = pCurMat->m_fTransparency;<\/p>\n glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT, pCurMat->m_fAmbient); glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, pCurMat->m_fDiffuse); glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, pCurMat->m_fSpecular); glMaterialfv(GL_FRONT_AND_BACK, GL_EMISSION, pCurMat->m_fEmissive); glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, pCurMat->m_fShininess); glEnable(GL_BLEND);<\/p>\n glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);<\/p>\n \/\/Texture map<\/p>\n pCurMat->m_Texture. Bind();<\/p>\n }<\/p>\n else<\/p>\n glDisable(GL_BLEND);<\/p>\n This little bit of code should be easy to follow. Because each model is broken into meshes, you must loop through them and draw them one at a time. The first thing to do is check to see whether the mesh does indeed have a material attached to it. If the material index of the mesh is not -1, a pointer to the appropriate material is obtained. Now you are almost ready to send the material information to OpenGL; how\u00adever, you first must take care of transparency. This is done by taking the transparency variable and using it to replace the alpha value of the diffuse property. Once that simple operation is completed, you can set<\/p>\n <\/p>\n \n\n| \n<\/td>\n<\/tr>\n<\/table>\n ~\u0413\u0413^3-<\/p>\n the material properties. Every property except Shininess uses glMaterialfv. This is because all other values are arrays of values, whereas shininess is simply a single float.<\/p>\n The next section simply turns on blending and sets the appropriate blending mode. This assures that transparency will work correctly and will minimize any funny visual artifacts.<\/p>\n Last, using the CImage class that you used to load the skin earlier, you bind the texture to the mesh.<\/p>\n If there is no material for the group, you must make sure to turn off blending. Failure to do so can cause very strange visual artifacts and unwanted graphical glitches. You can also use glMaterial to set the materials back to default. The default values for ambient, diffuse, specular, emissive materials are (0.2, 0.2, 0.2, 1.0), (0.8,0.8,0.8,1.0), (0.0,0.0,0.0,1.0), and (0.0,0.0,0.0,1.0), respectively. The shininess material is also set to 0.<\/p>\n The code that sends the vertices to the rendering system follows:<\/p>\n \/\/Draw mesh<\/p>\n glBegin(GL_TRIANGLES);<\/p>\n for(int y = 0; y < m_pMeshes[x].m_usNumTris; y++)<\/p>\n {<\/p>\n \/\/Get a pointer to the current triangle<\/p>\n SMs3dTriangle * pCurTri = &m_pTriangles[m_pMeshes[x].m_uspIndices[y]];<\/p>\n \/\/Send the normal<\/p>\n glNormal3fv(pCurTri->m_vNormals[0].Get());<\/p>\n \/\/Send texture coords<\/p>\n glTexCoord2f(pCurTri->m_fTexCoords[0][0], pCurTri->m_fTexCoords[1][0]);<\/p>\n \/\/Send vertex position<\/p>\n glVertex3fv(m_pVertices[pCurTri->m_usVertIndices[0]].m_vVert. Get()); glNormal3fv(pCurTri->m_vNormals[1].Get());<\/p>\n glTexCoord2f(pCurTri->m_fTexCoords[0][1], pCurTri->m_fTexCoords[1][1]); glVertex3fv(m_pVertices[pCurTri->m_usVertIndices[1]].m_vVert. Get());<\/p>\n glNormal3fv(pCurTri->m_vNormals[2].Get());<\/p>\n glTexCoord2f(pCurTri->m_fTexCoords[0][2], pCurTri->m_fTexCoords[1][2]); glVertex3fv(m_pVertices[pCurTri->m_usVertIndices[2]].m_vVert. Get());<\/p>\n }<\/p>\n<\/p>\n }<\/p>\n Just as you loop through each mesh, you must loop through each triangle within the mesh itself. After acquiring a pointer to the appro\u00adpriate triangle structure in the face array, you can send the normal vector, texture coordinates, and vertex position to OpenGL. This must be done three times for each triangle and once for each vertex.<\/p>\n Animation<\/a><\/p>\nThis is the part you have all been waiting for. The first section that uses what you learned in Chapter 5, \u201cIntroduction to Skeletal Animation\u201d (you did read that didn\u2019t you?)<\/p>\n First thing you have to do is finish loading the model. The remaining part of the model contains the joint (bone) data, including their names, initial positions, and keyframes.<\/p>\n Like the other section of the ms3d file, the joints structure is preceded by a two-byte integer that tells how many joints the file contains. Then comes the data. The joints and accompanying structures are fairly complicated, so bear with me.<\/p>\n First, the simple structure. This structure is used for storing the rota\u00adtion and translation of the keyframes:<\/p>\n \/\/—————————————————————————————<\/p>\n \/\/- SMs3dKeyFrame<\/p>\n \/\/- Rotation\/Translation information for joints struct SMs3dKeyFrame {<\/p>\n float m_fTime; float m_fParam[3];<\/p>\n };<\/p>\n This is a simple enough structure. The keyframe structure stores a single \u201cstop point\u201d or landmark of the model. The first variable, fTime, stores the time in seconds that this keyframe would be used to set the position of the particular joint. The second variable is an array of three floats. They store the rotations around the X, Y, and Z axes, or they<\/p>\n <\/p>\n | | | | | | | | |
![\"MlLkShflFE](\"\/img\/825\/image084.jpg\" "\\"MlLkShflFE")
<\/p>\n<\/td>\n<\/tr>\n<\/table>\n![\"MlLkShflFE](\"\/img\/825\/image086.jpg\" "\\"MlLkShflFE")
<\/p>\n<\/td>\n<\/tr>\n<\/table>\n![\"MlLkShflFE](\"\/img\/825\/image088.jpg\" "\\"MlLkShflFE")
<\/p>\n![\"MlLkShflFE](\"\/img\/825\/image090.jpg\" "\\"MlLkShflFE")
<\/p>\n<\/td>\n<\/tr>\n<\/table>\n![\"MlLkShflFE](\"\/img\/825\/image101.jpg\" "\\"MlLkShflFE")
<\/p>\n<\/td>\n<\/tr>\n<\/table>\n![\"MlLkShflFE](\"\/img\/825\/image103.jpg\" "\\"MlLkShflFE")
<\/p>\n