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在像素著色器中使用HLSL的內(nèi)建函數(shù)tex*XXXX給紋理采樣。注意：采樣時(shí)引用紋理上圖素的坐標(biāo)索引和采樣器狀態(tài)來(lái)生成像素。
通常這些函數(shù)需要我們做2件事：
使用紋理中的索引建立(u, v)紋理坐標(biāo)。
給特定的紋理中編入索引。
將紋理坐標(biāo)（u, v）輸入到像素著色器，在一個(gè)指定的HLSL對(duì)象中的像素著色器中，我們想編入索引的紋理是在像素著色器中被定義過(guò)的，在HLSL中叫作采樣器。（The particular texture that we want to index into is identified in the pixel shader by a special HLSL object called a sampler.），我們可以把采樣器對(duì)象想象成定義紋理和采樣器階段的對(duì)象。例如：假如我們使用3張紋理，這意味著我們需要在像素著色器里能夠引用3個(gè)階段中的每個(gè)一個(gè)。在像素著色器中我們這樣寫：
|
sampler FirstTex;
sampler SecondTex;
sampler ThirdTex;
|
Direct3D將給每個(gè)采樣器對(duì)象連接一個(gè)唯一的紋理級(jí)別(stage)，在應(yīng)用程序中我們找出與采樣器對(duì)象相關(guān)聯(lián)的階段，并設(shè)置相應(yīng)的紋理和采樣器狀態(tài)給該階段。下列代碼將舉例說(shuō)明如何在應(yīng)用程序中設(shè)置紋理并把采樣器狀態(tài)設(shè)置為FirstTex：
// 創(chuàng)建
IDirect3DTexture9* Tex;
D3DXCreateTextureFromFile(Device, "tex.bmp", &Tex);
… …
// 取得常量FirstTex的句柄
FirstTexHandle = MultiTexCT->GetConstantByName(0, "FirstTex");
// 取得常量的描述
D3DXCONSTANT_DESC FirstTexDesc;
UINT count;
MultiTexCT->GetConstantDesc(FirstTexHandle, &FirstTexDesc, &count);
… …
// 為FirstTex設(shè)置紋理和采樣器狀態(tài).
// We identify the stage FirstTex is associated with from the D3DXCONSTANT_DESC::RegisterIndex member:
Device->SetTexture(FirstTexDesc.RegisterIndex, Tex);
Device->SetSamplerState(FirstTexDesc.RegisterIndex, D3DSAMP_MAGFILTER, D3DTEXF_LINEAR);
Device->SetSamplerState(FirstTexDesc.RegisterIndex, D3DSAMP_MINFILTER, D3DTEXF_LINEAR);
Device->SetSamplerState(FirstTexDesc.RegisterIndex, D3DSAMP_MIPFILTER, D3DTEXF_LINEAR);
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注意：作為選擇，替換使用采樣器類型，你可以使用更多特殊的、強(qiáng)大的類型，如：sampler1D，sampler2D，sampler3D，和samplerCube類型，這些類型更安全并且它們只使用tex*函數(shù)。例如：一個(gè)sampler2D對(duì)象只使用tex2D*函數(shù)，同樣一個(gè)sampler3D對(duì)象只使用tex3D*函數(shù)。
18.5例子程序：Multitexturing in a Pixel Shader
這章中的例子演示了在像素著色器中使用多紋理，這個(gè)例子渲染的目標(biāo)是一個(gè)木箱紋理，一個(gè)聚光燈紋理，和一個(gè)包含字符串的紋理。這就是例子程序：Pixel Shader。
這個(gè)例子可以不使用像素著色器來(lái)實(shí)現(xiàn)，但實(shí)現(xiàn)這個(gè)程序是簡(jiǎn)單直接，它允許我們示范如何編寫，創(chuàng)建，而且使用像素著色器實(shí)現(xiàn)一些特效不必使用那些復(fù)雜的算法。
雖然在這個(gè)例子中一次只使用3張紋理，檢查采樣器對(duì)象的成員以確定每個(gè)像素著色器能夠使用的版本，這是值得的。換句話說(shuō)，我們一次能使用多少紋理，這依賴于使用的像素著色器的版本:
像素著色器的版本ps_1_1到 ps_1_3支持4個(gè)紋理采樣器。
像素著色器的版本ps_1_4支持6個(gè)紋理采樣器。
像素著色器的版本ps_2_0到 ps_3_0支持16個(gè)紋理采樣器。
/******************************************************************************
Pixel shader that does multi texturing.
******************************************************************************/
sampler g_base_texture;
sampler g_spotlight_texture;
sampler g_string_texture;
struct sPixelInput
{
float2 base : TEXCOORD0;
float2 spotlight : TEXCOORD1;
float2 text : TEXCOORD2;
};
struct sPixelOutput
{
vector diffuse : COLOR0;
};
/////////////////////////////////////////////////////////////////////////////////
sPixelOutput main(sPixelInput input)
{
sPixelOutput output = (sPixelOutput) 0;
// sample appropriate textures
vector base_color = tex2D(g_base_texture, input.base);
vector spotlight_color = tex2D(g_spotlight_texture, input.spotlight);
vector text_color = tex2D(g_string_texture, input.text);
// combine texel colors
vector color = base_color * spotlight_color + text_color;
// increase the intensity of the pixel slightly
color += 0.1f;
// save the resulting pixel color
output.diffuse = color;
return output;
}
tex2D的函數(shù)使用說(shuō)明如下:
There are two overloaded tex2D texture lookup functions:
- 2D texture lookup
- 2D texture lookup with partial derivatives
2D texture lookup
This function performs a 2D texture lookup.
Syntax
Where:
| Name | In/Out | Template Type | Component Type | Size |
| s |
in |
object |
sampler2D |
1 |
| t |
in |
vector |
float |
2 |
| ret |
out |
vector |
float |
4 |
2D texture lookup with partial derivatives
This function performs a 2D texture lookup also, but also uses the partial derivatives to help pick the LOD.
Syntax
| ret tex2D(s, t, ddx, ddy) |
Where:
| Name | In/Out | Template Type | Component Type | Size |
| s |
in |
object |
sampler2D |
1 |
| t |
in |
vector |
float |
2 |
| ddx |
in |
vector |
float |
2 |
| ddy |
in |
vector |
float |
2 |
| ret |
out |
vector |
float |
4 |
首先像素著色器定義了3個(gè)sampler對(duì)象，要渲染的每個(gè)紋理，接下來(lái)定義是input和output結(jié)構(gòu)。注意：我們沒有將任何的顏色值輸入到像素著色器中，這是因?yàn)槲覀兪褂眉y理自己的顏色和光照；即BaseTex保存表面的顏色，SpotLightTex是光照?qǐng)D。像素著色器輸出只一個(gè)簡(jiǎn)顏色值，指定了我們計(jì)算過(guò)的這個(gè)特定像素的顏色。
Main函數(shù)使用tex2D函數(shù)采樣3個(gè)紋理，即它取得每個(gè)紋理的圖素，計(jì)算映射到的像素，這通常依賴于指定的紋理坐標(biāo)和采樣器對(duì)象。然后我們混合圖素的顏色用公式：c = b * s + t。接下來(lái)我們讓全部的像素變亮一個(gè)bit，給每個(gè)部分增加0.1f。最后我們保存結(jié)果像素顏色并返回它。
執(zhí)行程序：
/**************************************************************************************************
Deomstrates multi-texturing using a pixel shader. You will have to switch to the REF
device to run this sample if your hardware doesn't support pixel shaders.
**************************************************************************************************/
#include "d3dUtility.h"
#pragma warning(disable : 4100)
struct sMultiTextureVertex
{
sMultiTextureVertex(float x, float y, float z,
float u0, float v0,
float u1, float v1,
float u2, float v2)
{
_x = x; _y = y; _z = z;
_u0 = u0; _v0 = v0;
_u1 = u1; _v1 = v1;
_u2 = u2, _v2 = v2;
}
float _x, _y, _z;
float _u0, _v0;
float _u1, _v1;
float _u2, _v2;
};
const DWORD MULTI_TEXTURE_VERTEX_FVF = D3DFVF_XYZ | D3DFVF_TEX3;
/////////////////////////////////////////////////////////////////////////////////////////////
const int WIDTH = 640;
const int HEIGHT = 480;
IDirect3DDevice9* g_device;
IDirect3DPixelShader9* g_pixel_shader;
ID3DXConstantTable* g_constant_table;
IDirect3DVertexBuffer9* g_vertex_buffer;
IDirect3DTexture9* g_base_texture;
IDirect3DTexture9* g_spotlight_texture;
IDirect3DTexture9* g_string_texture;
D3DXHANDLE g_base_texture_handle;
D3DXHANDLE g_spotlight_texture_handle;
D3DXHANDLE g_string_texture_handle;
D3DXCONSTANT_DESC g_base_texture_desc;
D3DXCONSTANT_DESC g_spotlight_texture_desc;
D3DXCONSTANT_DESC g_string_texture_desc;
////////////////////////////////////////////////////////////////////////////////////////////////////
bool setup()
{
// create geometry
g_device->CreateVertexBuffer(6 * sizeof(sMultiTextureVertex), D3DUSAGE_WRITEONLY,
MULTI_TEXTURE_VERTEX_FVF, D3DPOOL_MANAGED, &g_vertex_buffer, NULL);
sMultiTextureVertex* v;
g_vertex_buffer->Lock(0, 0, (void**)&v, 0);
v[0] = sMultiTextureVertex(-10.0f, -10.0f, 5.0f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, 1.0f);
v[1] = sMultiTextureVertex(-10.0f, 10.0f, 5.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f);
v[2] = sMultiTextureVertex( 10.0f, 10.0f, 5.0f, 1.0f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f);
v[3] = sMultiTextureVertex(-10.0f, -10.0f, 5.0f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f, 1.0f);
v[4] = sMultiTextureVertex( 10.0f, 10.0f, 5.0f, 1.0f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f);
v[5] = sMultiTextureVertex( 10.0f, -10.0f, 5.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f);
g_vertex_buffer->Unlock();
// compile shader
ID3DXBuffer* shader_buffer;
ID3DXBuffer* error_buffer;
HRESULT hr = D3DXCompileShaderFromFile("MultiTextureShader.cxx", NULL, NULL, "main", "ps_2_0", D3DXSHADER_DEBUG,
&shader_buffer, &error_buffer, &g_constant_table);
// output any error messages
if(error_buffer)
{
MessageBox(NULL, (char*) error_buffer->GetBufferPointer(), "ERROR", MB_OK);
safe_release<ID3DXBuffer*>(error_buffer);
}
if(FAILED(hr))
{
MessageBox(NULL, "D3DXCompileShaderFromFile() - FAILED", "ERROR", MB_OK);
return false;
}
hr = g_device->CreatePixelShader((DWORD*) shader_buffer->GetBufferPointer(), &g_pixel_shader);
if(FAILED(hr))
{
MessageBox(NULL, "CreatePixelShader - FAILED", "ERROR", MB_OK);
return false;
}
safe_release<ID3DXBuffer*>(shader_buffer);
// load textures
D3DXCreateTextureFromFile(g_device, "crate.bmp", &g_base_texture);
D3DXCreateTextureFromFile(g_device, "spotlight.bmp", &g_spotlight_texture);
D3DXCreateTextureFromFile(g_device, "text.bmp", &g_string_texture);
// get handles
g_base_texture_handle = g_constant_table->GetConstantByName(NULL, "g_base_texture");
g_spotlight_texture_handle = g_constant_table->GetConstantByName(NULL, "g_spotlight_texture");
g_string_texture_handle = g_constant_table->GetConstantByName(NULL, "g_string_texture");
// set constant descriptions
UINT count;
g_constant_table->GetConstantDesc(g_base_texture_handle, &g_base_texture_desc, &count);
g_constant_table->GetConstantDesc(g_spotlight_texture_handle, &g_spotlight_texture_desc, &count);
g_constant_table->GetConstantDesc(g_string_texture_handle, &g_string_texture_desc, &count);
g_constant_table->SetDefaults(g_device);
// set the projection matrix
D3DXMATRIX proj;
D3DXMatrixPerspectiveFovLH(&proj, D3DX_PI/4.0f, (float)WIDTH/HEIGHT, 1.0f, 1000.0f);
g_device->SetTransform(D3DTS_PROJECTION, &proj);
//g_device->SetRenderState(D3DRS_FILLMODE, D3DFILL_WIREFRAME);
return true;
}
///////////////////////////////////////////////////////////////////////////////////////////////////////
void cleanup()
{
safe_release<IDirect3DVertexBuffer9*>(g_vertex_buffer);
safe_release<IDirect3DTexture9*>(g_base_texture);
safe_release<IDirect3DTexture9*>(g_spotlight_texture);
safe_release<IDirect3DTexture9*>(g_string_texture);
safe_release<IDirect3DPixelShader9*>(g_pixel_shader);
safe_release<ID3DXConstantTable*>(g_constant_table);
}
///////////////////////////////////////////////////////////////////////////////////////////////////////
bool display(float time_delta)
{
// update the scene: allow user to rotate around scene.
static float angle = (3.0f * D3DX_PI) / 2.0f;
static float radius = 20.0f;
if(GetAsyncKeyState(VK_LEFT) & 0x8000f)
angle -= 0.5f * time_delta;
if(GetAsyncKeyState(VK_RIGHT) & 0x8000f)
angle += 0.5f * time_delta;
if(GetAsyncKeyState(VK_UP) & 0x8000f)
radius -= 2.0f * time_delta;
if(GetAsyncKeyState(VK_DOWN) & 0x8000f)
radius += 2.0f * time_delta;
D3DXVECTOR3 position(cosf(angle) * radius, 0.0f, sinf(angle) * radius);
D3DXVECTOR3 target(0.0f, 0.0f, 0.0f);
D3DXVECTOR3 up(0.0f, 1.0f, 0.0f);
D3DXMATRIX view_matrix;
D3DXMatrixLookAtLH(&view_matrix, &position, &target, &up);
g_device->SetTransform(D3DTS_VIEW, &view_matrix);
// render now
g_device->Clear(0, NULL, D3DCLEAR_TARGET | D3DCLEAR_ZBUFFER, 0xFFFFFFFF, 1.0f, 0);
g_device->BeginScene();
g_device->SetPixelShader(g_pixel_shader);
g_device->SetFVF(MULTI_TEXTURE_VERTEX_FVF);
g_device->SetStreamSource(0, g_vertex_buffer, 0, sizeof(sMultiTextureVertex));
// base texture
g_device->SetTexture(g_base_texture_desc.RegisterIndex, g_base_texture);
g_device->SetSamplerState(g_base_texture_desc.RegisterIndex, D3DSAMP_MAGFILTER, D3DTEXF_LINEAR);
g_device->SetSamplerState(g_base_texture_desc.RegisterIndex, D3DSAMP_MINFILTER, D3DTEXF_LINEAR);
g_device->SetSamplerState(g_base_texture_desc.RegisterIndex, D3DSAMP_MIPFILTER, D3DTEXF_LINEAR);
// spotlight texture
g_device->SetTexture(g_spotlight_texture_desc.RegisterIndex, g_spotlight_texture);
g_device->SetSamplerState(g_spotlight_texture_desc.RegisterIndex, D3DSAMP_MAGFILTER, D3DTEXF_LINEAR);
g_device->SetSamplerState(g_spotlight_texture_desc.RegisterIndex, D3DSAMP_MINFILTER, D3DTEXF_LINEAR);
g_device->SetSamplerState(g_spotlight_texture_desc.RegisterIndex, D3DSAMP_MIPFILTER, D3DTEXF_LINEAR);
// string texture
g_device->SetTexture(g_string_texture_desc.RegisterIndex, g_string_texture);
g_device->SetSamplerState(g_string_texture_desc.RegisterIndex, D3DSAMP_MAGFILTER, D3DTEXF_LINEAR);
g_device->SetSamplerState(g_string_texture_desc.RegisterIndex, D3DSAMP_MINFILTER, D3DTEXF_LINEAR);
g_device->SetSamplerState(g_string_texture_desc.RegisterIndex, D3DSAMP_MIPFILTER, D3DTEXF_LINEAR);
g_device->DrawPrimitive(D3DPT_TRIANGLELIST, 0, 2);
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;
}
setup函數(shù)執(zhí)行下列功能：
填充方形的頂點(diǎn)緩存
編譯著像素色器
創(chuàng)建像素色器
讀取紋理
設(shè)置投影矩陣，不使用光照
取得采樣器(sampler)對(duì)象的句柄
取得采樣器對(duì)象的描述
display函數(shù)設(shè)置像素著色器，使用2個(gè)紋理，并且在渲染方格前設(shè)置他們對(duì)應(yīng)的采樣器狀態(tài)。
運(yùn)行截圖：
下載源程序