3ds.cpp

3DS文件读取程序 用于三维开发的；用于三维开发的；

	return vResult;								// Return the resultant vector
}

// This divides a vector by a single number (scalar) and returns the result
CVector3 DivideVectorByScaler(CVector3 vVector1, float Scaler)
{
	CVector3 vResult;							// The variable to hold the resultant vector
	
	vResult.x = vVector1.x / Scaler;			// Divide Vector1's x value by the scaler
	vResult.y = vVector1.y / Scaler;			// Divide Vector1's y value by the scaler
	vResult.z = vVector1.z / Scaler;			// Divide Vector1's z value by the scaler

	return vResult;								// Return the resultant vector
}

// This returns the cross product between 2 vectors
CVector3 Cross(CVector3 vVector1, CVector3 vVector2)
{
	CVector3 vCross;								// The vector to hold the cross product
												// Get the X value
	vCross.x = ((vVector1.y * vVector2.z) - (vVector1.z * vVector2.y));
												// Get the Y value
	vCross.y = ((vVector1.z * vVector2.x) - (vVector1.x * vVector2.z));
												// Get the Z value
	vCross.z = ((vVector1.x * vVector2.y) - (vVector1.y * vVector2.x));

	return vCross;								// Return the cross product
}

// This returns the normal of a vector
CVector3 Normalize(CVector3 vNormal)
{
	double Magnitude;							// This holds the magitude			

	Magnitude = Mag(vNormal);					// Get the magnitude

	vNormal.x /= (float)Magnitude;				// Divide the vector's X by the magnitude
	vNormal.y /= (float)Magnitude;				// Divide the vector's Y by the magnitude
	vNormal.z /= (float)Magnitude;				// Divide the vector's Z by the magnitude

	return vNormal;								// Return the normal
}

///////////////////////////////// COMPUTER NORMALS \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*
/////
/////	This function computes the normals and vertex normals of the objects
/////
///////////////////////////////// COMPUTER NORMALS \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*

void CLoad3DS::ComputeNormals(t3DModel *pModel)
{
	CVector3 vVector1, vVector2, vNormal, vPoly[3];

	// If there are no objects, we can skip this part
	if(pModel->numOfObjects <= 0)
		return;

	// What are vertex normals?  And how are they different from other normals?
	// Well, if you find the normal to a triangle, you are finding a "Face Normal".
	// If you give OpenGL a face normal for lighting, it will make your object look
	// really flat and not very round.  If we find the normal for each vertex, it makes
	// the smooth lighting look.  This also covers up blocky looking objects and they appear
	// to have more polygons than they do.    Basically, what you do is first
	// calculate the face normals, then you take the average of all the normals around each
	// vertex.  It's just averaging.  That way you get a better approximation for that vertex.

	// Go through each of the objects to calculate their normals
	for(int index = 0; index < pModel->numOfObjects; index++)
	{
		// Get the current object
		t3DObject *pObject = &(pModel->pObject[index]);

		// Here we allocate all the memory we need to calculate the normals
		CVector3 *pNormals		= new CVector3 [pObject->numOfFaces];
		CVector3 *pTempNormals	= new CVector3 [pObject->numOfFaces];
		pObject->pNormals		= new CVector3 [pObject->numOfVerts];

		// Go though all of the faces of this object
		for(int i=0; i < pObject->numOfFaces; i++)
		{												
			// To cut down LARGE code, we extract the 3 points of this face
			vPoly[0] = pObject->pVerts[pObject->pFaces[i].vertIndex[0]];
			vPoly[1] = pObject->pVerts[pObject->pFaces[i].vertIndex[1]];
			vPoly[2] = pObject->pVerts[pObject->pFaces[i].vertIndex[2]];

			// Now let's calculate the face normals (Get 2 vectors and find the cross product of those 2)

			vVector1 = Vector(vPoly[0], vPoly[2]);		// Get the vector of the polygon (we just need 2 sides for the normal)
			vVector2 = Vector(vPoly[2], vPoly[1]);		// Get a second vector of the polygon

			vNormal  = Cross(vVector1, vVector2);		// Return the cross product of the 2 vectors (normalize vector, but not a unit vector)
			pTempNormals[i] = vNormal;					// Save the un-normalized normal for the vertex normals
			vNormal  = Normalize(vNormal);				// Normalize the cross product to give us the polygons normal

			pNormals[i] = vNormal;						// Assign the normal to the list of normals
		}

		//////////////// Now Get The Vertex Normals /////////////////

		CVector3 vSum = {0.0, 0.0, 0.0};
		CVector3 vZero = vSum;
		int shared=0;

		for (i = 0; i < pObject->numOfVerts; i++)			// Go through all of the vertices
		{
			for (int j = 0; j < pObject->numOfFaces; j++)	// Go through all of the triangles
			{												// Check if the vertex is shared by another face
				if (pObject->pFaces[j].vertIndex[0] == i || 
					pObject->pFaces[j].vertIndex[1] == i || 
					pObject->pFaces[j].vertIndex[2] == i)
				{
					vSum = AddVector(vSum, pTempNormals[j]);// Add the un-normalized normal of the shared face
					shared++;								// Increase the number of shared triangles
				}
			}      
			
			// Get the normal by dividing the sum by the shared.  We negate the shared so it has the normals pointing out.
			pObject->pNormals[i] = DivideVectorByScaler(vSum, float(-shared));

			// Normalize the normal for the final vertex normal
			pObject->pNormals[i] = Normalize(pObject->pNormals[i]);	

			vSum = vZero;									// Reset the sum
			shared = 0;										// Reset the shared
		}
	
		// Free our memory and start over on the next object
		delete [] pTempNormals;
		delete [] pNormals;
	}
}


/////////////////////////////////////////////////////////////////////////////////
//
// * QUICK NOTES * 
//
// This was a HUGE amount of knowledge and probably the largest tutorial yet!
// In the next tutorial we will show you how to load a text file format called .obj.
// This is the most common 3D file format that almost ANY 3D software will import.
//
// Once again I should point out that the coordinate system of OpenGL and 3DS Max are different.
// Since 3D Studio Max Models with the Z-Axis pointing up (strange and ugly I know! :), 
// we need to flip the y values with the z values in our vertices.  That way it
// will be normal, with Y pointing up.  Also, because we swap the Y and Z we need to negate 
// the Z to make it come out correctly.  This is also explained and done in ReadVertices().
//
// CHUNKS: What is a chunk anyway?
// 
// "The chunk ID is a unique code which identifies the type of data in this chunk 
// and also may indicate the existence of subordinate chunks. The chunk length indicates 
// the length of following data to be associated with this chunk. Note, this may 
// contain more data than just this chunk. If the length of data is greater than that 
// needed to fill in the information for the chunk, additional subordinate chunks are 
// attached to this chunk immediately following any data needed for this chunk, and 
// should be parsed out. These subordinate chunks may themselves contain subordinate chunks. 
// Unfortunately, there is no indication of the length of data, which is owned by the current 
// chunk, only the total length of data attached to the chunk, which means that the only way 
// to parse out subordinate chunks is to know the exact format of the owning chunk. On the 
// other hand, if a chunk is unknown, the parsing program can skip the entire chunk and 
// subordinate chunks in one jump. " - Jeff Lewis ([e-mail])
//
// In a short amount of words, a chunk is defined this way:
// 2 bytes - Stores the chunk ID (OBJECT, MATERIAL, PRIMARY, etc...)
// 4 bytes - Stores the length of that chunk.  That way you know when that
//           chunk is done and there is a new chunk.
//
// So, to start reading the 3DS file, you read the first 2 bytes of it, then
// the length (using fread()).  It should be the PRIMARY chunk, otherwise it isn't
// a .3DS file.  
//
// Below is a list of the order that you will find the chunks and all the know chunks.
// If you go to www.wosit.org you can find a few documents on the 3DS file format.
// You can also take a look at the 3DS Format.rtf that is included with this tutorial.
//
//
//
//      MAIN3DS  (0x4D4D)
//     |
//     +--EDIT3DS  (0x3D3D)
//     |  |
//     |  +--EDIT_MATERIAL (0xAFFF)
//     |  |  |
//     |  |  +--MAT_NAME01 (0xA000) (See mli Doc) 
//     |  |
//     |  +--EDIT_CONFIG1  (0x0100)
//     |  +--EDIT_CONFIG2  (0x3E3D) 
//     |  +--EDIT_VIEW_P1  (0x7012)
//     |  |  |
//     |  |  +--TOP            (0x0001)
//     |  |  +--BOTTOM         (0x0002)
//     |  |  +--LEFT           (0x0003)
//     |  |  +--RIGHT          (0x0004)
//     |  |  +--FRONT          (0x0005) 
//     |  |  +--BACK           (0x0006)
//     |  |  +--USER           (0x0007)
//     |  |  +--CAMERA         (0xFFFF)
//     |  |  +--LIGHT          (0x0009)
//     |  |  +--DISABLED       (0x0010)  
//     |  |  +--BOGUS          (0x0011)
//     |  |
//     |  +--EDIT_VIEW_P2  (0x7011)
//     |  |  |
//     |  |  +--TOP            (0x0001)
//     |  |  +--BOTTOM         (0x0002)
//     |  |  +--LEFT           (0x0003)
//     |  |  +--RIGHT          (0x0004)
//     |  |  +--FRONT          (0x0005) 
//     |  |  +--BACK           (0x0006)
//     |  |  +--USER           (0x0007)
//     |  |  +--CAMERA         (0xFFFF)
//     |  |  +--LIGHT          (0x0009)
//     |  |  +--DISABLED       (0x0010)  
//     |  |  +--BOGUS          (0x0011)
//     |  |
//     |  +--EDIT_VIEW_P3  (0x7020)
//     |  +--EDIT_VIEW1    (0x7001) 
//     |  +--EDIT_BACKGR   (0x1200) 
//     |  +--EDIT_AMBIENT  (0x2100)
//     |  +--EDIT_OBJECT   (0x4000)
//     |  |  |
//     |  |  +--OBJ_TRIMESH   (0x4100)      
//     |  |  |  |
//     |  |  |  +--TRI_VERTEXL          (0x4110) 
//     |  |  |  +--TRI_VERTEXOPTIONS    (0x4111)
//     |  |  |  +--TRI_MAPPINGCOORS     (0x4140) 
//     |  |  |  +--TRI_MAPPINGSTANDARD  (0x4170)
//     |  |  |  +--TRI_FACEL1           (0x4120)
//     |  |  |  |  |
//     |  |  |  |  +--TRI_SMOOTH            (0x4150)   
//     |  |  |  |  +--TRI_MATERIAL          (0x4130)
//     |  |  |  |
//     |  |  |  +--TRI_LOCAL            (0x4160)
//     |  |  |  +--TRI_VISIBLE          (0x4165)
//     |  |  |
//     |  |  +--OBJ_LIGHT    (0x4600)
//     |  |  |  |
//     |  |  |  +--LIT_OFF              (0x4620)
//     |  |  |  +--LIT_SPOT             (0x4610) 
//     |  |  |  +--LIT_UNKNWN01         (0x465A) 
//     |  |  | 
//     |  |  +--OBJ_CAMERA   (0x4700)
//     |  |  |  |
//     |  |  |  +--CAM_UNKNWN01         (0x4710)
//     |  |  |  +--CAM_UNKNWN02         (0x4720)  
//     |  |  |
//     |  |  +--OBJ_UNKNWN01 (0x4710)
//     |  |  +--OBJ_UNKNWN02 (0x4720)
//     |  |
//     |  +--EDIT_UNKNW01  (0x1100)
//     |  +--EDIT_UNKNW02  (0x1201) 
//     |  +--EDIT_UNKNW03  (0x1300)
//     |  +--EDIT_UNKNW04  (0x1400)
//     |  +--EDIT_UNKNW05  (0x1420)
//     |  +--EDIT_UNKNW06  (0x1450)
//     |  +--EDIT_UNKNW07  (0x1500)
//     |  +--EDIT_UNKNW08  (0x2200)
//     |  +--EDIT_UNKNW09  (0x2201)
//     |  +--EDIT_UNKNW10  (0x2210)
//     |  +--EDIT_UNKNW11  (0x2300)
//     |  +--EDIT_UNKNW12  (0x2302)
//     |  +--EDIT_UNKNW13  (0x2000)
//     |  +--EDIT_UNKNW14  (0xAFFF)
//     |
//     +--KEYF3DS (0xB000)
//        |
//        +--KEYF_UNKNWN01 (0xB00A)
//        +--............. (0x7001) ( viewport, same as editor )
//        +--KEYF_FRAMES   (0xB008)
//        +--KEYF_UNKNWN02 (0xB009)
//        +--KEYF_OBJDES   (0xB002)
//           |
//           +--KEYF_OBJHIERARCH  (0xB010)
//           +--KEYF_OBJDUMMYNAME (0xB011)
//           +--KEYF_OBJUNKNWN01  (0xB013)
//           +--KEYF_OBJUNKNWN02  (0xB014)
//           +--KEYF_OBJUNKNWN03  (0xB015)  
//           +--KEYF_OBJPIVOT     (0xB020)  
//           +--KEYF_OBJUNKNWN04  (0xB021)  
//           +--KEYF_OBJUNKNWN05  (0xB022)  
//
// Once you know how to read chunks, all you have to know is the ID you are looking for
// and what data is stored after that ID.  You need to get the file format for that.
// I can give it to you if you want, or you can go to www.wosit.org for several versions.
// Because this is a proprietary format, it isn't a official document.
//
// I know there was a LOT of information blown over, but it is too much knowledge for
// one tutorial.  In the animation tutorial that I eventually will get to, some of
// the things explained here will be explained in more detail.  I do not claim that
// this is the best .3DS tutorial, or even a GOOD one :)  But it is a good start, and there
// isn't much code out there that is simple when it comes to reading .3DS files.
// So far, this is the best I have seen.  That is why I made it :)
// 
// I would like to thank www.wosit.org and Terry Caton ([e-mail]) for his help on this.
//
// Let me know if this helps you out!
// 
// 
// Ben Humphrey (DigiBen)
// Game Programmer
// [e-mail]
// Co-Web Host of www.GameTutorials.com
//
//