OpenGL繪制曲線OpenGL通過(guò)求值器產(chǎn)生曲線和曲面可以生成任意角度的多項(xiàng)式曲線可以將其他類(lèi)型的多邊形曲線和曲面轉(zhuǎn)換成貝塞爾曲線和曲面達(dá)到應(yīng)用所需的精度步一：設(shè)定求值器voidglMap1{fd}(GLenumtarget,TYPEu1,TYPEu2,

GLintstride,

GLintorder,constTYPE*points);參數(shù)target的取值參數(shù)意義GL_MAP1_VERTEX_3x,y,z頂點(diǎn)坐標(biāo)GL_MAP1_VERTEX_4x,y,z,w

頂點(diǎn)坐標(biāo)GL_MAP1_INDEX顏色表GL_MAP1_COLOR_4R,G,B,AGL_MAP1_NORMAL法向量GL_MAP1_TEXTURE_COORD_1s紋理坐標(biāo)GL_MAP1_TEXTURE_COORD_2s,t紋理坐標(biāo)GL_MAP1_TEXTURE_COORD_3s,t,r紋理坐標(biāo)GL_MAP1_TEXTURE_COORD_4s,t,r,q紋理坐標(biāo)步二：?jiǎn)?dòng)求值器glEnable();/*參數(shù)與glMap1*()的第一個(gè)參數(shù)一致*/關(guān)閉求值器函數(shù)為

glDisable()步三：調(diào)用計(jì)算坐標(biāo)函數(shù)方法一voidglEvalCoord1{fd}[v](TYPEu);/*將u值傳給所有已啟動(dòng)的求值器，然后由這些已啟動(dòng)的求值器生成坐標(biāo)、法向量、顏色或紋理坐標(biāo)，每調(diào)用一次只產(chǎn)生一個(gè)坐標(biāo)*/方法二voidglMapGrid1{fd}(GLintn,TYPEu1,TYPEu2);/*定義一個(gè)間隔相等的一維網(wǎng)格*/voidglEvalMesh1(GLenummode,

GLintp1,GLintp2);/*將求值器應(yīng)用在網(wǎng)格上，計(jì)算相應(yīng)的坐標(biāo)值，調(diào)用一次產(chǎn)生一組坐標(biāo)*/Example:

GLfloatctrlpoints[4][3]={

{-4.0,-4.0,0.0},{-2.0,4.0,0.0},

{2.0,

-4.0,0.0},{4.0,

4.0,0.0}};glMap1f(GL_MAP1_VERTEX_3,0.0,1.0,3,4,

&ctrlpoints[0][0]);glEnable(GL_MAP1_VERTEX_3);glBegin(GL_LINE_STRIP);

for(i=0;i<=30;i++)

glEvalCoord1f((GLfloat)i/30.0);glEnd();以下兩段代碼等價(jià)glBegin(GL_POINT);

/*glBegin(GL_LINE_STRIP);*/

for(i=p1;i<=p2;i++)

glEvalCoord1(u1+i*(u2-u1)/n);

glEnd();glMapGrid1f(n,u1,u2);glEvalMesh1(GL_POINT,p1,p2);例1：Bezier曲線二維曲面voidglMapGrid2{fd}(GLenumnu,TYPEu1,TYPEu2,

GLenum

nv,TYPEv1,TYPEv2);

voidglEvalMesh2(GLenummode,

GLintp1,GLintp2,