3ds.cpp

3DS文件读取程序 用于三维开发的；用于三维开发的；

	// The current chunk to work with
	tChunk currentChunk = {0};

	// Continue to read these chunks until we read the end of this sub chunk
	while (pPreviousChunk->bytesRead < pPreviousChunk->length)
	{
		// Read the next chunk
		ReadChunk(&currentChunk);

		// Check which chunk we just read in
		switch (currentChunk.ID)
		{
		case MATNAME:							// This chunk holds the name of the material
			
			// Here we read in the material name
			currentChunk.bytesRead += fread(pModel->pMaterials[pModel->numOfMaterials - 1].strName, 1, currentChunk.length - currentChunk.bytesRead, m_FilePointer);
			break;

		case MATDIFFUSE:						// This holds the R G B color of our object
			ReadColorChunk(&(pModel->pMaterials[pModel->numOfMaterials - 1]), &currentChunk);
			break;
		
		case MATMAP:							// This is the header for the texture info
			
			// Proceed to read in the material information
			ProcessNextMaterialChunk(pModel, &currentChunk);
			break;

		case MATMAPFILE:						// This stores the file name of the material

			// Here we read in the material's file name
			currentChunk.bytesRead += fread(pModel->pMaterials[pModel->numOfMaterials - 1].strFile, 1, currentChunk.length - currentChunk.bytesRead, m_FilePointer);
			break;
		
		default:  

			// Read past the ignored or unknown chunks
			currentChunk.bytesRead += fread(gBuffer, 1, currentChunk.length - currentChunk.bytesRead, m_FilePointer);
			break;
		}

		// Add the bytes read from the last chunk to the previous chunk passed in.
		pPreviousChunk->bytesRead += currentChunk.bytesRead;
	}
}

///////////////////////////////// READ CHUNK \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*
/////
/////	This function reads in a chunk ID and it's length in bytes
/////
///////////////////////////////// READ CHUNK \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*

void CLoad3DS::ReadChunk(tChunk *pChunk)
{
	// This reads the chunk ID which is 2 bytes.
	// The chunk ID is like OBJECT or MATERIAL.  It tells what data is
	// able to be read in within the chunks section.  
	pChunk->bytesRead = fread(&pChunk->ID, 1, 2, m_FilePointer);

	// Then, we read the length of the chunk which is 4 bytes.
	// This is how we know how much to read in, or read past.
	pChunk->bytesRead += fread(&pChunk->length, 1, 4, m_FilePointer);
}

///////////////////////////////// GET STRING \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*
/////
/////	This function reads in a string of characters
/////
///////////////////////////////// GET STRING \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*

int CLoad3DS::GetString(char *pBuffer)
{
	int index = 0;

	// Read 1 byte of data which is the first letter of the string
	fread(pBuffer, 1, 1, m_FilePointer);

	// Loop until we get NULL
	while (*(pBuffer + index++) != 0) {

		// Read in a character at a time until we hit NULL.
		fread(pBuffer + index, 1, 1, m_FilePointer);
	}

	// Return the string length, which is how many bytes we read in (including the NULL)
	return strlen(pBuffer) + 1;
}


///////////////////////////////// READ COLOR \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*
/////
/////	This function reads in the RGB color data
/////
///////////////////////////////// READ COLOR \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*

void CLoad3DS::ReadColorChunk(tMaterialInfo *pMaterial, tChunk *pChunk)
{
	tChunk tempChunk = {0};

	// Read the color chunk info
	ReadChunk(&tempChunk);

	// Read in the R G B color (3 bytes - 0 through 255)
	tempChunk.bytesRead += fread(pMaterial->color, 1, tempChunk.length - tempChunk.bytesRead, m_FilePointer);

	// Add the bytes read to our chunk
	pChunk->bytesRead += tempChunk.bytesRead;
}


///////////////////////////////// READ VERTEX INDECES \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*
/////
/////	This function reads in the indices for the vertex array
/////
///////////////////////////////// READ VERTEX INDECES \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*

void CLoad3DS::ReadVertexIndices(t3DObject *pObject, tChunk *pPreviousChunk)
{
	unsigned short index = 0;					// This is used to read in the current face index

	// In order to read in the vertex indices for the object, we need to first
	// read in the number of them, then read them in.  Remember,
	// we only want 3 of the 4 values read in for each face.  The fourth is
	// a visibility flag for 3D Studio Max that doesn't mean anything to us.

	// Read in the number of faces that are in this object (int)
	pPreviousChunk->bytesRead += fread(&pObject->numOfFaces, 1, 2, m_FilePointer);

	// Alloc enough memory for the faces and initialize the structure
	pObject->pFaces = new tFace [pObject->numOfFaces];
	memset(pObject->pFaces, 0, sizeof(tFace) * pObject->numOfFaces);

	// Go through all of the faces in this object
	for(int i = 0; i < pObject->numOfFaces; i++)
	{
		// Next, we read in the A then B then C index for the face, but ignore the 4th value.
		// The fourth value is a visibility flag for 3D Studio Max, we don't care about this.
		for(int j = 0; j < 4; j++)
		{
			// Read the first vertice index for the current face 
			pPreviousChunk->bytesRead += fread(&index, 1, sizeof(index), m_FilePointer);

			if(j < 3)
			{
				// Store the index in our face structure.
				pObject->pFaces[i].vertIndex[j] = index;
			}
		}
	}
}


///////////////////////////////// READ UV COORDINATES \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*
/////
/////	This function reads in the UV coordinates for the object
/////
///////////////////////////////// READ UV COORDINATES \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*

void CLoad3DS::ReadUVCoordinates(t3DObject *pObject, tChunk *pPreviousChunk)
{
	// In order to read in the UV indices for the object, we need to first
	// read in the amount there are, then read them in.

	// Read in the number of UV coordinates there are (int)
	pPreviousChunk->bytesRead += fread(&pObject->numTexVertex, 1, 2, m_FilePointer);

	// Allocate memory to hold the UV coordinates
	pObject->pTexVerts = new CVector2 [pObject->numTexVertex];

	// Read in the texture coodinates (an array 2 float)
	pPreviousChunk->bytesRead += fread(pObject->pTexVerts, 1, pPreviousChunk->length - pPreviousChunk->bytesRead, m_FilePointer);
}


///////////////////////////////// READ VERTICES \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*
/////
/////	This function reads in the vertices for the object
/////
///////////////////////////////// READ VERTICES \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*

void CLoad3DS::ReadVertices(t3DObject *pObject, tChunk *pPreviousChunk)
{
	// Like most chunks, before we read in the actual vertices, we need
	// to find out how many there are to read in.  Once we have that number
	// we then fread() them into our vertice array.

	// Read in the number of vertices (int)
	pPreviousChunk->bytesRead += fread(&(pObject->numOfVerts), 1, 2, m_FilePointer);

	// Allocate the memory for the verts and initialize the structure
	pObject->pVerts = new CVector3 [pObject->numOfVerts];
	memset(pObject->pVerts, 0, sizeof(CVector3) * pObject->numOfVerts);

	// Read in the array of vertices (an array of 3 floats)
	pPreviousChunk->bytesRead += fread(pObject->pVerts, 1, pPreviousChunk->length - pPreviousChunk->bytesRead, m_FilePointer);

	// Now we should have all of the vertices read in.  Because 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.  If you prefer to work with Z pointing
	// up, then just delete this next loop.  Also, because we swap the Y and Z
	// we need to negate the Z to make it come out correctly.

	// Go through all of the vertices that we just read and swap the Y and Z values
	for(int i = 0; i < pObject->numOfVerts; i++)
	{
		// Store off the Y value
		float fTempY = pObject->pVerts[i].y;

		// Set the Y value to the Z value
		pObject->pVerts[i].y = pObject->pVerts[i].z;

		// Set the Z value to the Y value, 
		// but negative Z because 3D Studio max does the opposite.
		pObject->pVerts[i].z = -fTempY;
	}
}


///////////////////////////////// READ OBJECT MATERIAL \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*
/////
/////	This function reads in the material name assigned to the object and sets the materialID
/////
///////////////////////////////// READ OBJECT MATERIAL \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\*

void CLoad3DS::ReadObjectMaterial(t3DModel *pModel, t3DObject *pObject, tChunk *pPreviousChunk)
{
	char strMaterial[255] = {0};			// This is used to hold the objects material name

	// *What is a material?*  - A material is either the color or the texture map of the object.
	// It can also hold other information like the brightness, shine, etc... Stuff we don't
	// really care about.  We just want the color, or the texture map file name really.

	// Here we read the material name that is assigned to the current object.
	// strMaterial should now have a string of the material name, like "Material #2" etc..
	pPreviousChunk->bytesRead += GetString(strMaterial);

	// Now that we have a material name, we need to go through all of the materials
	// and check the name against each material.  When we find a material in our material
	// list that matches this name we just read in, then we assign the materialID
	// of the object to that material index.  You will notice that we passed in the
	// model to this function.  This is because we need the number of textures.
	// Yes though, we could have just passed in the model and not the object too.

	// Go through all of the textures
	for(int i = 0; i < pModel->numOfMaterials; i++)
	{
		// If the material we just read in matches the current texture name
		if(strcmp(strMaterial, pModel->pMaterials[i].strName) == 0)
		{
			// Set the material ID to the current index 'i' and stop checking
			pObject->materialID = i;

			// Now that we found the material, check if it's a texture map.
			// If the strFile has a string length of 1 and over it's a texture
			if(strlen(pModel->pMaterials[i].strFile) > 0) {

				// Set the object's flag to say it has a texture map to bind.
				pObject->bHasTexture = true;
			}	
			break;
		}
		else
		{
			// Set the ID to -1 to show there is no material for this object
			pObject->materialID = -1;
		}
	}

	// Read past the rest of the chunk since we don't care about shared vertices
	// You will notice we subtract the bytes already read in this chunk from the total length.
	pPreviousChunk->bytesRead += fread(gBuffer, 1, pPreviousChunk->length - pPreviousChunk->bytesRead, m_FilePointer);
}			

// *Note* 
//
// Below are some math functions for calculating vertex normals.  We want vertex normals
// because it makes the lighting look really smooth and life like.  You probably already
// have these functions in the rest of your engine, so you can delete these and call
// your own.  I wanted to add them so I could show how to calculate vertex normals.

//////////////////////////////	Math Functions  ////////////////////////////////*

// This computes the magnitude of a normal.   (magnitude = sqrt(x^2 + y^2 + z^2)
#define Mag(Normal) (sqrt(Normal.x*Normal.x + Normal.y*Normal.y + Normal.z*Normal.z))

// This calculates a vector between 2 points and returns the result
CVector3 Vector(CVector3 vPoint1, CVector3 vPoint2)
{
	CVector3 vVector;							// The variable to hold the resultant vector

	vVector.x = vPoint1.x - vPoint2.x;			// Subtract point1 and point2 x's
	vVector.y = vPoint1.y - vPoint2.y;			// Subtract point1 and point2 y's
	vVector.z = vPoint1.z - vPoint2.z;			// Subtract point1 and point2 z's

	return vVector;								// Return the resultant vector
}

// This adds 2 vectors together and returns the result
CVector3 AddVector(CVector3 vVector1, CVector3 vVector2)
{
	CVector3 vResult;							// The variable to hold the resultant vector
	
	vResult.x = vVector2.x + vVector1.x;		// Add Vector1 and Vector2 x's
	vResult.y = vVector2.y + vVector1.y;		// Add Vector1 and Vector2 y's
	vResult.z = vVector2.z + vVector1.z;		// Add Vector1 and Vector2 z's