黑暗貼圖動畫

可以通過黑暗貼圖三種調(diào)制操作的切換來創(chuàng)建一個動畫示例，代碼如下所示：

pd3dDevice->SetTexture(0, g_base_texture);
pd3dDevice->SetTextureStageState(0, D3DTSS_TEXCOORDINDEX,	0);
pd3dDevice->SetTextureStageState(0, D3DTSS_COLORARG1,		D3DTA_TEXTURE);
pd3dDevice->SetTextureStageState(0, D3DTSS_COLOROP,		D3DTOP_SELECTARG1);

pd3dDevice->SetTexture(1, g_dark_texture);
pd3dDevice->SetTextureStageState(1, D3DTSS_TEXCOORDINDEX,	0);
pd3dDevice->SetTextureStageState(1, D3DTSS_COLORARG1,		D3DTA_TEXTURE);
pd3dDevice->SetTextureStageState(1, D3DTSS_COLORARG2,		D3DTA_CURRENT);

static double last_time = 0.0f;
double interval = fTime - last_time;

if(interval < 0.5f)
	pd3dDevice->SetTextureStageState(1, D3DTSS_COLOROP, D3DTOP_MODULATE);
else if(interval > 0.5f && interval < 1.0f)
	pd3dDevice->SetTextureStageState(1, D3DTSS_COLOROP, D3DTOP_MODULATE2X);
else if(interval > 1.0f && interval < 1.5f)
	pd3dDevice->SetTextureStageState(1, D3DTSS_COLOROP, D3DTOP_MODULATE4X);
else if(interval > 1.5f)
	last_time = fTime;

效果如下：

混合紋理與頂點漫反射顏色

當很強的陽光照射在物體表面上時，會使它表面的顏色變得更加明亮，這可以通過將紋理與頂點的漫反射顏色相混合來模擬這種效果。當一個白色材質(zhì)反射一個方向光時，反射量越多，就意味著紋理顏色在最終顯示結(jié)果中所占的成分越少。因此，那些被光直接照射到表面會呈現(xiàn)出白色。示例代碼如下：

// setup light

ZeroMemory(&g_light, sizeof(D3DLIGHT9));

g_light.Type = D3DLIGHT_DIRECTIONAL;
g_light.Diffuse.r = 0.5f;
g_light.Diffuse.g = 0.5f;
g_light.Diffuse.b = 0.5f;

D3DXVECTOR3 light_dir(0, 0, 10);
D3DXVec3Normalize((D3DXVECTOR3*) &g_light.Direction, &light_dir);

// setup material

ZeroMemory(&g_material, sizeof(D3DMATERIAL9));

g_material.Ambient.r = 1.0f;
g_material.Ambient.g = 1.0f;
g_material.Ambient.b = 1.0f;
g_material.Ambient.a = 1.0f;
g_material.Diffuse.r = 0.7f;
g_material.Diffuse.g = 0.7f;
g_material.Diffuse.b = 0.7f;
g_material.Diffuse.a = 0.5f;

pd3dDevice->SetRenderState(D3DRS_LIGHTING, TRUE);
pd3dDevice->SetRenderState(D3DRS_AMBIENT, 0x00808080);
pd3dDevice->SetLight(0, &g_light);
pd3dDevice->LightEnable(0, TRUE);
pd3dDevice->SetMaterial(&g_material);

pd3dDevice->SetTexture(0, g_base_texture);
pd3dDevice->SetTextureStageState(0, D3DTSS_TEXCOORDINDEX, 0);
pd3dDevice->SetTextureStageState(0, D3DTSS_COLORARG1, D3DTA_TEXTURE);
pd3dDevice->SetTextureStageState(0, D3DTSS_COLORARG2, D3DTA_DIFFUSE);
pd3dDevice->SetTextureStageState(0, D3DTSS_COLOROP, D3DTOP_ADD);
pd3dDevice->SetTextureStageState(1, D3DTSS_COLOROP, D3DTOP_DISABLE);
 

運行效果：

這個效果只需一次渲染，因此這里沒有多重紋理的代碼，對這段代碼的簡單描述就是"基礎(chǔ)貼圖 + 漫反射插值"。

在固定函數(shù)流水線中有三種獲取漫反射顏色的途徑（在可編程流水線中則有更多的途徑）：材質(zhì)、漫反射頂點顏色、鏡面反射頂點顏色。從何處獲取漫反射顏色取決于渲染狀態(tài)D3DRS_DIFFUSEMATERIALSOURCE的設(shè)定。例如，如果調(diào)用：

pd3dDevice->SetRenderState(D3DRS_DIFFUSEMATERIALSOURCE, D3DMCS_MATERIAL);

D3DRS_DIFFUSEMATERIALSOURCE

Diffuse color source for lighting calculations. Valid values are members of the D3DMATERIALCOLORSOURCE enumerated type. The default value is D3DMCS_COLOR1. The value for this render state is used only if the D3DRS_COLORVERTEX render state is set to TRUE.

D3DMATERIALCOLORSOURCE

Defines the location at which a color or color component must be accessed for lighting calculations.

typedef enum D3DMATERIALCOLORSOURCE
{
    D3DMCS_MATERIAL = 0,
    D3DMCS_COLOR1 = 1,
    D3DMCS_COLOR2 = 2,
    D3DMCS_FORCE_DWORD = 0x7fffffff,
} D3DMATERIALCOLORSOURCE, *LPD3DMATERIALCOLORSOURCE;

Constants

D3DMCS_MATERIAL

Use the color from the current material.

D3DMCS_COLOR1

Use the diffuse vertex color.

D3DMCS_COLOR2

Use the specular vertex color.

D3DMCS_FORCE_DWORD

Forces this enumeration to compile to 32 bits in size. Without this value, some compilers would allow this enumeration to compile to a size other than 32 bits. This value is not used.

Remarks

These flags are used to set the value of the following render states in the D3DRENDERSTATETYPE enumerated type.

• D3DRS_AMBIENTMATERIALSOURCE
• D3DRS_DIFFUSEMATERIALSOURCE
• D3DRS_EMISSIVEMATERIALSOURCE
• D3DRS_SPECULARMATERIALSOURCE

混合黑暗貼圖與頂點漫反射顏色

試想，當你站在一間伸手不見五指的房間內(nèi)，無法看清周圍的任何顏色。于是你打開燈光，突然之間物體的顏色便呈現(xiàn)了出來，就好像是被火焰點燃了一樣。對于這種效果，可以通過黑暗貼圖和頂點漫反射顏色的混合來模擬。

先將一張紋理與一個頂點的漫反射顏色相混合，再將這個結(jié)果與黑暗貼圖相混合：

pd3dDevice->SetRenderState(D3DRS_LIGHTING, TRUE);
pd3dDevice->SetRenderState(D3DRS_AMBIENT, 0x0080FFFF);
pd3dDevice->SetLight(0, &g_light);
pd3dDevice->LightEnable(0, TRUE);
pd3dDevice->SetMaterial(&g_material);

pd3dDevice->SetTexture(0, g_base_texture);
pd3dDevice->SetTextureStageState(0, D3DTSS_TEXCOORDINDEX, 0);
pd3dDevice->SetTextureStageState(0, D3DTSS_COLORARG1, D3DTA_TEXTURE);
pd3dDevice->SetTextureStageState(0, D3DTSS_COLORARG2, D3DTA_DIFFUSE);
pd3dDevice->SetTextureStageState(0, D3DTSS_COLOROP, D3DTOP_MODULATE);

pd3dDevice->SetTexture(1, g_dark_texture);
pd3dDevice->SetTextureStageState(1, D3DTSS_TEXCOORDINDEX, 0);
pd3dDevice->SetTextureStageState(1, D3DTSS_COLORARG1, D3DTA_TEXTURE);
pd3dDevice->SetTextureStageState(1, D3DTSS_COLORARG2, D3DTA_CURRENT);
pd3dDevice->SetTextureStageState(1, D3DTSS_COLOROP, D3DTOP_MODULATE);

運行效果：

如果沒有光照，則紋理顏色會乘以0，因此就看不到墻壁紋理了，在這種情況下將只能看到第二張紋理。如果第一張紋理是不可見的，則第一階段的顏色值0與第二階段的顏色相乘的結(jié)果仍將為0（黑色）。當沒有光照在物體的某個表面上時，該面的第一張紋理顏色會減弱為黑色。當你身處一個真正漆黑的地方時，由于光照微弱，你是無法看到周圍物體的顏色的，因此上面這段代碼對于模擬這種情況非常有效。

這個過程可以描述為"（基礎(chǔ)貼圖 x 頂點的漫反射顏色） x 黑暗貼圖"