11.2.4
產(chǎn)生頂點(diǎn)法線(xiàn)
一個(gè)X文件不包含頂點(diǎn)法線(xiàn)數(shù)據(jù)，這是很有可能的。假如是這種情況，那么手動(dòng)計(jì)算頂點(diǎn)法線(xiàn)以便我們能夠使用燈光這是很有必要的。現(xiàn)在知道了ID3DXMesh接口和它的父接口ID3DXBaseMesh，我們能夠使用下面的函數(shù)來(lái)產(chǎn)生任何mesh的頂點(diǎn)法線(xiàn)：
Computes unit normals for each vertex in a mesh.
Provided to support legacy applications. Use D3DXComputeTangentFrameEx for
better results.
HRESULT D3DXComputeNormals(
LPD3DXBASEMESH pMesh,
CONST DWORD * pAdjacency
);
Parameters
- pMesh
- [in, out] Pointer to an ID3DXBaseMesh interface,
representing the normalized mesh object. This function may not take an
ID3DXPMesh progressive mesh as input.
- pAdjacency
- [in] Pointer to an array of three DWORDs per face
that specify the three neighbors for each face in the created progressive
mesh. This parameter is optional and should be set to NULL if it is unused.
Return Values
If the function succeeds, the return value is S_OK. If
the function fails, the return value can be one of the following:
D3DERR_INVALIDCALL, D3DXERR_INVALIDDATA, E_OUTOFMEMORY.
Remarks
The input mesh must have the D3DFVF_NORMAL flag
specified in its flexible vertex format (FVF).
A normal for a vertex is generated by averaging the
normals of all faces that share that vertex.
If adjacency is provided, replicated vertices are
ignored and "smoothed" over. If adjacency is not provided, replicated vertices
will have normals averaged in from only the faces explicitly referencing them.
This function simply calls D3DXComputeTangentFrameEx
with the following input parameters:
D3DXComputeTangentFrameEx( pMesh,
D3DX_DEFAULT,
0,
D3DX_DEFAULT,
0,
D3DX_DEFAULT,
0,
D3DDECLUSAGE_NORMAL,
0,
D3DXTANGENT_GENERATE_IN_PLACE | D3DXTANGENT_CALCULATE_NORMALS,
pAdjacency,
-1.01f,
-0.01f,
-1.01f,
NULL,
NULL);
這個(gè)函數(shù)通過(guò)使用平均法線(xiàn)的方法來(lái)產(chǎn)生頂點(diǎn)法線(xiàn)。假如有鄰接信息，那么重復(fù)的頂點(diǎn)是被忽略的。假如沒(méi)有鄰接信息，那么重復(fù)的頂點(diǎn)也會(huì)被重復(fù)計(jì)算。了解這些是很重要的，我們檢查pMash必須有一個(gè)包含D3DFVF_NORMAL標(biāo)記的頂點(diǎn)格式。
注意假如X文件不包含頂點(diǎn)法線(xiàn)數(shù)據(jù)，那么通過(guò)D3DXLoadMeshFromX創(chuàng)建的ID3DXMesh對(duì)象在它的頂點(diǎn)格式中沒(méi)有指定的D3DFVF_NORMAL標(biāo)記。因此，在我們能夠使用D3DXComputeNormals之前，我們必須克隆mesh并且為其指定包含D3DFVF_NORMAL的頂點(diǎn)格式。下面就是相應(yīng)的代碼：
|
// does the
mesh have a D3DFVF_NORMAL in its vertex format?
if
( !(pMesh->GetFVF() & D3DFVF_NORMAL) )
{
// no, so clone a new mesh and add
D3DFVF_NORMAL to its format:
ID3DXMesh* pTempMesh
= 0;
pMesh->CloneMeshFVF(
D3DXMESH_MANAGED,
pMesh->GetFVF() | D3DFVF_NORMAL, // add it
here
Device,
&pTempMesh );
// compute the normals:
D3DXComputeNormals(
pTempMesh, NULL );
pMesh->Release();
// get rid of the old mesh
pMesh = pTempMesh;
// save the new mesh with normals
}
|
11.3漸進(jìn)網(wǎng)格（Progressive
Meshes）
漸進(jìn)網(wǎng)格，它通過(guò)ID3DXPMesh接口來(lái)表現(xiàn)，允許我們通過(guò)邊縮減轉(zhuǎn)換（edge
collapse transformations，ECT）來(lái)簡(jiǎn)化mesh。每執(zhí)行一次ECT就移除一個(gè)頂點(diǎn)和一或2個(gè)面。因?yàn)槊總€(gè)ECT是可逆的（它的逆過(guò)程叫頂點(diǎn)分裂），我們能夠逆轉(zhuǎn)簡(jiǎn)化過(guò)程并且恢復(fù)mesh為它的原始狀態(tài)。當(dāng)然，我們不可能得到比原始情況還要精細(xì)的網(wǎng)格。我們僅僅只能簡(jiǎn)化然后恢復(fù)簡(jiǎn)化操作。圖11.2顯示了同一個(gè)mesh的三種不同精細(xì)級(jí)別（levels
of detail，LOD）：高，中，低。
漸進(jìn)網(wǎng)格和mipmaps紋理非常相似。當(dāng)使用紋理時(shí)，我們已經(jīng)注意到在一個(gè)小或遠(yuǎn)的圖元上使用高分辨率的紋理簡(jiǎn)直就是浪費(fèi)。對(duì)于mesh也是同樣的道理，一個(gè)小或遠(yuǎn)的mesh不需要太多三角形，多了也是浪費(fèi)。因此，我們不會(huì)花費(fèi)渲染高三角形模型的時(shí)間來(lái)渲染一個(gè)只需要表現(xiàn)小的低三角形模型。
我們可以使用漸進(jìn)網(wǎng)格來(lái)根據(jù)模型距離攝象機(jī)的距離來(lái)調(diào)整模型的LOD。也就是說(shuō)，當(dāng)距離減少時(shí)，我們?cè)黾觤esh的細(xì)節(jié)，當(dāng)距離增加時(shí)我們減少mesh的細(xì)節(jié)。
11.3.1
產(chǎn)生一個(gè)漸進(jìn)網(wǎng)格
我們能夠使用下面的函數(shù)來(lái)創(chuàng)建一個(gè)ID3DXPMesh對(duì)象：
|
HRESULT D3DXGeneratePMesh(
LPD3DXMESH pMesh,
CONST DWORD
*pAdjacency,
CONST
LPD3DXATTRIBUTEWEIGHTS pVertexAttributeWeights,
CONST FLOAT
*pVertexWeights,
DWORD MinValue,
DWORD Options,
LPD3DXPMESH *ppPMesh
);
|
pMesh— 輸入原始mesh，它包含了我們想要生成的漸進(jìn)網(wǎng)格的mesh數(shù)據(jù)。
pAdjacency
— 指向一個(gè)包含pMesh鄰接信息的DWORD數(shù)組。
pVertexAttributeWeights — 指向一個(gè)D3DXATTRIBUTEWEIGHTS數(shù)組，它的大小是pMesh->GetNumVertices()。它的第i項(xiàng)與pMesh中的第i個(gè)頂點(diǎn)相對(duì)應(yīng)并且指定的是它的品質(zhì)權(quán)重。品質(zhì)權(quán)重被用來(lái)確定一個(gè)頂點(diǎn)被刪除的可能性大小。你能夠?qū)⒋藚?shù)設(shè)置為null，對(duì)于每個(gè)頂點(diǎn)一個(gè)默認(rèn)的頂點(diǎn)品質(zhì)權(quán)重將被設(shè)置。
pVertexWeights
— 指向一個(gè)float數(shù)組，它的大小是pMesh->GetNumVertices()，它的第i項(xiàng)與pMesh中的第i個(gè)頂點(diǎn)相對(duì)應(yīng)并且指定的是它的頂點(diǎn)權(quán)重。頂點(diǎn)權(quán)重越高被刪除的可能性越小。你能夠?qū)⒋藚?shù)設(shè)置為null，對(duì)于每個(gè)頂點(diǎn)一個(gè)默認(rèn)的頂點(diǎn)品質(zhì)權(quán)重1.0將被設(shè)置。
MinValue
— 我們想要簡(jiǎn)化到的最小頂點(diǎn)或面數(shù)。注意該值是必須的，而且與頂點(diǎn)/品質(zhì)權(quán)重有關(guān)，最終可能達(dá)不到該值。
Options
— 只能取D3DXMESHSIMP枚舉類(lèi)型中的一個(gè)值：
D3DXMESHSIMP_VERTEX —
指定在上一個(gè)參數(shù)MinValue中提到的數(shù)為頂點(diǎn)數(shù)。
D3DXMESHSIMP_FACE
—指定在上一個(gè)參數(shù)MinValue中提到的數(shù)為面數(shù)。
ppPMesh
— 返回生成好的漸進(jìn)網(wǎng)格。
11.3.2
頂點(diǎn)品質(zhì)權(quán)重
Specifies mesh weight attributes.
typedef struct D3DXATTRIBUTEWEIGHTS {
FLOAT Position;
FLOAT Boundary;
FLOAT Normal;
FLOAT Diffuse;
FLOAT Specular;
FLOAT Texcoord[8];
FLOAT Tangent;
FLOAT Binormal;
} D3DXATTRIBUTEWEIGHTS, *LPD3DXATTRIBUTEWEIGHTS;
Members
- Position
- Position.
- Boundary
- Blend weight.
- Normal
- Normal.
- Diffuse
- Diffuse lighting value.
- Specular
- Specular lighting value.
- Texcoord
- Eight texture coordinates.
- Tangent
- Tangent.
- Binormal
- Binormal.
Remarks
This structure describes how a simplification operation
will consider vertex data when calculating relative costs between collapsing
edges. For example, if the Normal field is 0.0, the simplification operation
will ignore the vertex normal component when calculating the error for the
collapse. However, if the Normal field is 1.0, the simplification operation will
use the vertex normal component. If the Normal field is 2.0, double the amount
of errors; if the Normal field is 4.0, then quadruple the number of errors, and
so on.
The LPD3DXATTRIBUTEWEIGHTS type is defined as a pointer
to the D3DXATTRIBUTEWEIGHTS structure.
typedef D3DXATTRIBUTEWEIGHTS* LPD3DXATTRIBUTEWEIGHTS;
頂點(diǎn)權(quán)重結(jié)構(gòu)允許我們?yōu)槊總€(gè)頂點(diǎn)屬性指定一個(gè)權(quán)值。0.0表示該屬性沒(méi)有權(quán)重。頂點(diǎn)屬性的權(quán)重越高在簡(jiǎn)化過(guò)程中被移除的可能性越小。默認(rèn)的權(quán)值如下：
|
D3DXATTRIBUTEWEIGHTS
AttributeWeights;
AttributeWeights.Position =
1.0;
AttributeWeights.Boundary =
1.0;
AttributeWeights.Normal =
1.0;
AttributeWeights.Diffuse =
0.0;
AttributeWeights.Specular =
0.0;
AttributeWeights.Tex[8] =
{0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0};
|
默認(rèn)的權(quán)值是被推薦的，除非你的應(yīng)用程序有一個(gè)重要的理由而不使用它。
11.3.3 ID3DXPMesh方法
ID3DXPMesh接口是繼承自ID3DXBaseMesh接口，下面是一些方法：
DWORD
GetMaxFaces(VOID)——返回漸進(jìn)網(wǎng)格能夠被設(shè)置的最大面數(shù)。
DWORD
GetMaxVertices(VOID)——返回漸進(jìn)網(wǎng)格能夠被設(shè)置的最大頂點(diǎn)數(shù)。
DWORD
GetMinFaces(VOID)——返回漸進(jìn)網(wǎng)格能夠被設(shè)置的最小面數(shù)。
DWORD
GetMinVertices(VOID)——返回漸進(jìn)網(wǎng)格能夠被設(shè)置的最小頂點(diǎn)數(shù)。
HRESULT
SetNumFaces(DWORD Faces)——這個(gè)方法允許我們?cè)O(shè)置面的個(gè)數(shù)，以便讓mesh簡(jiǎn)化/復(fù)雜化。例如，假設(shè)mesh目前有50個(gè)面，我們現(xiàn)在想將它簡(jiǎn)化到30個(gè)面；我們將寫(xiě)成：
注意調(diào)整后的面數(shù)可能并不是我們?cè)O(shè)定的面數(shù)。假如面數(shù)小于了GetMinFaces（），那么面數(shù)將為GetMinFaces（）。同樣的，假如面數(shù)大于了GetMaxFaces（），那么面數(shù)將為GetMaxFaces（）。
HRESULT
SetNumVertices(DWORD Vertices)——這個(gè)方法允許我們?cè)O(shè)置頂點(diǎn)的個(gè)數(shù)，以便讓mesh簡(jiǎn)化/復(fù)雜化。例如，假設(shè)mesh目前有20個(gè)頂點(diǎn)，我們現(xiàn)在想將它增加到40個(gè)；我們將寫(xiě)成：
|
pmesh->SetNumVertices(40);
|
注意調(diào)整后的頂點(diǎn)數(shù)可能并不是我們?cè)O(shè)定的數(shù)。假如頂點(diǎn)數(shù)小于了GetMinVertices（），那么頂點(diǎn)數(shù)將為GetMinVertices（）。同樣的，假如頂點(diǎn)數(shù)大于了GetMaxVertices（），那么頂點(diǎn)數(shù)將為GetMaxVertices（）。
HRESULT TrimByFaces(
DWORD NewFacesMin,
DWORD NewFacesMax,
DWORD *rgiFaceRemap,
// Face remap info.
DWORD *rgiVertRemap
// Vertex remap info.
);
這個(gè)方法允許我們?cè)O(shè)置新的最小和最大面數(shù)，分別通過(guò)NewFacesMin和NewFacesMax指定。注意新的最小和最大值必須在現(xiàn)有最小和最大面數(shù)之間；也就是說(shuō)，必須在[GetMinFaces（），GetMaxFaces（）]之中。該函數(shù)也返回面和頂點(diǎn)的重影射信息。
HRESULT
TrimByVertices(
DWORD
NewVerticesMin,
DWORD
NewVerticesMax,
DWORD *rgiFaceRemap,
// Face remap info.
DWORD *rgiVertRemap
// Vertex remap info.
);
這個(gè)方法允許我們?cè)O(shè)置新的最小和最大頂點(diǎn)數(shù)，分別通過(guò)NewVerticesMin和NewVerticesMax指定。注意新的最小和最大值必須在現(xiàn)有最小和最大頂點(diǎn)數(shù)之間；也就是說(shuō)，必須在[GetMinVertices（），GetMaxVertices（）]之中。
11.3.4實(shí)例程序：漸進(jìn)網(wǎng)格
漸進(jìn)網(wǎng)格例子與X文件例子很相似，除了實(shí)際上我們創(chuàng)建和渲染的是一個(gè)漸進(jìn)網(wǎng)格，通過(guò)ID3DXPMesh接口來(lái)表現(xiàn)。我們?cè)试S用戶(hù)通過(guò)鍵盤(pán)輸入進(jìn)行交互式地改變漸進(jìn)網(wǎng)格。你能通過(guò)按A鍵來(lái)增加mesh的面數(shù)，按S鍵來(lái)減少mesh的面數(shù)。
運(yùn)行截圖：
主程序：
/**************************************************************************************
Demonstrates how to use the progressive mesh interface (ID3DXPMesh).
Use the 'A' key to add triangles, use the 'S' key to remove triangles.
Note that we outline the triangles in yellow so that you can see them get
removed and added.
**************************************************************************************/
#include <vector>
#include "d3dUtility.h"
#pragma warning(disable : 4100)
using namespace std;
const int WIDTH = 640;
const int HEIGHT = 480;
IDirect3DDevice9* g_device;
ID3DXMesh* g_source_mesh;
ID3DXPMesh* g_pmesh;
vector<D3DMATERIAL9> g_materials;
vector<IDirect3DTexture9*> g_textures;
////////////////////////////////////////////////////////////////////////////////////////////////////
bool setup()
{
// load the XFile data
ID3DXBuffer* adjacency_buffer = NULL;
ID3DXBuffer* material_buffer = NULL;
DWORD num_material = 0;
HRESULT hr = D3DXLoadMeshFromX("bigship1.x", D3DXMESH_MANAGED, g_device, &adjacency_buffer, &material_buffer,
NULL, &num_material, &g_source_mesh);
if(FAILED(hr))
{
MessageBox(NULL, "D3DXLoadMeshFromX() - FAILED", "ERROR", MB_OK);
return false;
}
// extract the materials, and load textures.
if(material_buffer != NULL && num_material != 0)
{
D3DXMATERIAL* materials = (D3DXMATERIAL*) material_buffer->GetBufferPointer();
for(DWORD i = 0; i < num_material; i++)
{
// the MatD3D property doesn't have an ambient value set when it load, so set it now.
materials[i].MatD3D.Ambient = materials[i].MatD3D.Diffuse;
// save the ith material
g_materials.push_back(materials[i].MatD3D);
// check if the ith material has an associative texture
if(materials[i].pTextureFilename != NULL)
{
// yes, load the texture for the ith subset.
IDirect3DTexture9* texture;
D3DXCreateTextureFromFile(g_device, materials[i].pTextureFilename, &texture);
// save the loaded texture
g_textures.push_back(texture);
}
else
{
// no texture for the ith subset
g_textures.push_back(NULL);
}
}
}
safe_release<ID3DXBuffer*>(material_buffer);
// optimize the mesh
hr = g_source_mesh->OptimizeInplace(D3DXMESHOPT_ATTRSORT | D3DXMESHOPT_COMPACT | D3DXMESHOPT_VERTEXCACHE,
(DWORD*) adjacency_buffer->GetBufferPointer(),
(DWORD*) adjacency_buffer->GetBufferPointer(), // new adjacency info
NULL, NULL);
if(FAILED(hr))
{
MessageBox(NULL, "OptimizeInplace() - FAILED", "ERROR", MB_OK);
safe_release<ID3DXBuffer*>(adjacency_buffer);
return false;
}
// generate the progressive mesh
hr = D3DXGeneratePMesh(
g_source_mesh,
(DWORD*) adjacency_buffer->GetBufferPointer(),
NULL, // default vertex attribute weights
NULL, // default vertex weights
1, // simply as low as possible
D3DXMESHSIMP_FACE, // simplify by face count
&g_pmesh);
safe_release<ID3DXMesh*>(g_source_mesh);
safe_release<ID3DXBuffer*>(adjacency_buffer);
if(FAILED(hr))
{
MessageBox(NULL, "D3DXGeneratePMesh() - FAILED", "ERROR", MB_OK);
return false;
}
// set to original detail
DWORD max_faces = g_pmesh->GetMaxFaces();
g_pmesh->SetNumFaces(max_faces);
// set texture filters
g_device->SetSamplerState(0, D3DSAMP_MAGFILTER, D3DTEXF_LINEAR);
g_device->SetSamplerState(0, D3DSAMP_MINFILTER, D3DTEXF_LINEAR);
g_device->SetSamplerState(0, D3DSAMP_MIPFILTER, D3DTEXF_LINEAR);
// set lights
D3DXVECTOR3 dir(1.0f, -1.0f, 1.0f);
D3DXCOLOR color(1.0f, 1.0f, 1.0f, 1.0f);
D3DLIGHT9 light = init_directional_light(&dir, &color);
g_device->SetLight(0, &light);
g_device->LightEnable(0, TRUE);
g_device->SetRenderState(D3DRS_NORMALIZENORMALS, TRUE);
g_device->SetRenderState(D3DRS_SPECULARENABLE, TRUE);
// set camera
D3DXVECTOR3 pos(-8.0f, 4.0f, -12.0f);
D3DXVECTOR3 target(0.0f, 0.0f, 0.0f);
D3DXVECTOR3 up(0.0f, 1.0f, 0.0f);
D3DXMATRIX view_matrix;
D3DXMatrixLookAtLH(&view_matrix, &pos, &target, &up);
g_device->SetTransform(D3DTS_VIEW, &view_matrix);
// set the projection matrix
D3DXMATRIX proj;
D3DXMatrixPerspectiveFovLH(&proj, D3DX_PI * 0.5f, (float)WIDTH/HEIGHT, 1.0f, 1000.0f);
g_device->SetTransform(D3DTS_PROJECTION, &proj);
return true;
}
///////////////////////////////////////////////////////////////////////////////////////////////////////
void cleanup()
{
safe_release<ID3DXPMesh*>(g_pmesh);
for(DWORD i = 0; i < g_textures.size(); i++)
safe_release<IDirect3DTexture9*>(g_textures[i]);
}
///////////////////////////////////////////////////////////////////////////////////////////////////////
bool display(float time_delta)
{
// update: rotate the mesh
// get the current number of faces the pmesh has
DWORD num_faces = g_pmesh->GetNumFaces();
// Add a face, note the SetNumFaces() will automatically clamp the specified value
// if it goes out of bounds.
if(GetAsyncKeyState('A') & 0x8000f)
{
// Sometimes we must add more than one face to invert an edge collaps transformation
// because of the internal implementation details of the ID3DXPMesh interface.
// In other words, adding one face may possibly result in a mesh with the same number
// of faces as before. Thus to increase the face count we may some times have to add
// two faces at once.
g_pmesh->SetNumFaces(num_faces + 1);
if(g_pmesh->GetNumFaces() == num_faces)
g_pmesh->SetNumFaces(num_faces + 2);
}
// Remove a face, note the SetNumFaces() will automatically clamp the specified value
// if it goes out of bounds.
if(GetAsyncKeyState('S') & 0x8000f)
g_pmesh->SetNumFaces(num_faces - 1);
// render now
g_device->Clear(0, NULL, D3DCLEAR_TARGET | D3DCLEAR_ZBUFFER, 0x00000000, 1.0f, 0);
g_device->BeginScene();
for(DWORD i = 0; i < g_materials.size(); i++)
{
// draw pmesh
g_device->SetMaterial(&g_materials[i]);
g_device->SetTexture(0, g_textures[i]);
g_pmesh->DrawSubset(i);
// draw wireframe outline
g_device->SetMaterial(&YELLOW_MATERIAL);
g_device->SetRenderState(D3DRS_FILLMODE, D3DFILL_WIREFRAME);
g_pmesh->DrawSubset(i);
// restore solid mode
g_device->SetRenderState(D3DRS_FILLMODE, D3DFILL_SOLID);
}
g_device->EndScene();
g_device->Present(NULL, NULL, NULL, NULL);
return true;
}
///////////////////////////////////////////////////////////////////////////////////////////////////////
LRESULT CALLBACK wnd_proc(HWND hwnd, UINT msg, WPARAM word_param, LPARAM long_param)
{
switch(msg)
{
case WM_DESTROY:
PostQuitMessage(0);
break;
case WM_KEYDOWN:
if(word_param == VK_ESCAPE)
DestroyWindow(hwnd);
break;
}
return DefWindowProc(hwnd, msg, word_param, long_param);
}
///////////////////////////////////////////////////////////////////////////////////////////////////////
int WINAPI WinMain(HINSTANCE inst, HINSTANCE, PSTR cmd_line, int cmd_show)
{
if(! init_d3d(inst, WIDTH, HEIGHT, true, D3DDEVTYPE_HAL, &g_device))
{
MessageBox(NULL, "init_d3d() - failed.", 0, MB_OK);
return 0;
}
if(! setup())
{
MessageBox(NULL, "Steup() - failed.", 0, MB_OK);
return 0;
}
enter_msg_loop(display);
cleanup();
g_device->Release();
return 0;
}
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