材質(zhì)及光照示例

設(shè)置物體表面材料(Material)的反光屬性（顏色和材質(zhì)）的方法如下：

public void glMaterialf(int face,int pname,float param)
public void glMaterialfv(int face,int pname,float[] params,int offset)
public void glMaterialfv(int face,int pname,FloatBuffer params)

• face : 在OpenGL ES中只能使用GL_FRONT_AND_BACK，表示修改物體的前面和后面的材質(zhì)光線屬性。
• pname: 參數(shù)類型，可以有GL_AMBIENT, GL_DIFFUSE, GL_SPECULAR, GL_EMISSION, GL_SHININESS。這些參數(shù)用在光照方程。
• param：參數(shù)的值。

其中 GL_AMBIENT,GL_DIFFUSE,GL_SPECULAR ，GL_EMISSION 為顏色 RGBA 值，GL_SHININESS 值可以從0到128，值越大，光的散射越小：

http://wiki.jikexueyuan.com/project/opengl-es-guide/images/103.png" alt="" />

此外，方法 glLightModleXX 給出了光照模型的參數(shù)

public void glLightModelf(int pname,float param)
public void glLightModelfv(int pname,float[] params,int offset)
public void glLightModelfv(int pname,FloatBuffer params)

• pname：參數(shù)類型，可以為GL_LIGHT_MODEL_AMBIENT和GL_LIGHT_MODEL_TWO_SIDE
• params：參數(shù)的值。

最終頂點(diǎn)的顏色由這些參數(shù)（光源，材質(zhì)光學(xué)屬性，光照模型）綜合決定（光照方程計(jì)算出）。

下面例子在場(chǎng)景中設(shè)置一個(gè)白色光源：

public void initScene(GL10 gl){
 float[] amb = { 1.0f, 1.0f, 1.0f, 1.0f, };
 float[] diff = { 1.0f, 1.0f, 1.0f, 1.0f, };
 float[] spec = { 1.0f, 1.0f, 1.0f, 1.0f, };
 float[] pos = { 0.0f, 5.0f, 5.0f, 1.0f, };
 float[] spot_dir = { 0.0f, -1.0f, 0.0f, };
 gl.glEnable(GL10.GL\_DEPTH\_TEST);
 gl.glEnable(GL10.GL\_CULL\_FACE);
 gl.glEnable(GL10.GL\_LIGHTING);
 gl.glEnable(GL10.GL\_LIGHT0);
 ByteBuffer abb
 = ByteBuffer.allocateDirect(amb.length\*4);
 abb.order(ByteOrder.nativeOrder());
 FloatBuffer ambBuf = abb.asFloatBuffer();
 ambBuf.put(amb);
 ambBuf.position(0);
 ByteBuffer dbb
 = ByteBuffer.allocateDirect(diff.length\*4);
 dbb.order(ByteOrder.nativeOrder());
 FloatBuffer diffBuf = dbb.asFloatBuffer();
 diffBuf.put(diff);
 diffBuf.position(0);
 ByteBuffer sbb
 = ByteBuffer.allocateDirect(spec.length\*4);
 sbb.order(ByteOrder.nativeOrder());
 FloatBuffer specBuf = sbb.asFloatBuffer();
 specBuf.put(spec);
 specBuf.position(0);
 ByteBuffer pbb
 = ByteBuffer.allocateDirect(pos.length\*4);
 pbb.order(ByteOrder.nativeOrder());
 FloatBuffer posBuf = pbb.asFloatBuffer();
 posBuf.put(pos);
 posBuf.position(0);
 ByteBuffer spbb
 = ByteBuffer.allocateDirect(spot_dir.length\*4);
 spbb.order(ByteOrder.nativeOrder());
 FloatBuffer spot_dirBuf = spbb.asFloatBuffer();
 spot_dirBuf.put(spot_dir);
 spot_dirBuf.position(0);
 gl.glLightfv(GL10.GL\_LIGHT0, GL10.GL\_AMBIENT, ambBuf);
 gl.glLightfv(GL10.GL\_LIGHT0, GL10.GL\_DIFFUSE, diffBuf);
 gl.glLightfv(GL10.GL\_LIGHT0, GL10.GL\_SPECULAR, specBuf);
 gl.glLightfv(GL10.GL\_LIGHT0, GL10.GL\_POSITION, posBuf);
 gl.glLightfv(GL10.GL\_LIGHT0, GL10.GL\_SPOT\_DIRECTION,
 spot_dirBuf);
 gl.glLightf(GL10.GL\_LIGHT0, GL10.GL\_SPOT_EXPONENT, 0.0f);
 gl.glLightf(GL10.GL\_LIGHT0, GL10.GL\_SPOT\_CUTOFF, 45.0f);
 gl.glLoadIdentity();
 GLU.gluLookAt(gl,0.0f, 4.0f, 4.0f, 0.0f, 0.0f, 0.0f,
 0.0f, 1.0f, 0.0f);
}  

繪制一個(gè)球，并使用藍(lán)色材質(zhì)：

public void drawScene(GL10 gl) {
 super.drawScene(gl);
 float[] mat_amb = {0.2f \* 0.4f, 0.2f \* 0.4f,
 0.2f \* 1.0f, 1.0f,};
 float[] mat\_diff = {0.4f, 0.4f, 1.0f, 1.0f,};
 float[] mat\_spec = {1.0f, 1.0f, 1.0f, 1.0f,};
 ByteBuffer mabb
 = ByteBuffer.allocateDirect(mat\_amb.length*4);
 mabb.order(ByteOrder.nativeOrder());
 FloatBuffer mat\_ambBuf = mabb.asFloatBuffer();
 mat\_ambBuf.put(mat\_amb);
 mat\_ambBuf.position(0);
 ByteBuffer mdbb
 = ByteBuffer.allocateDirect(mat\_diff.length\*4);
 mdbb.order(ByteOrder.nativeOrder());
 FloatBuffer mat\_diffBuf = mdbb.asFloatBuffer();
 mat\_diffBuf.put(mat\_diff);
 mat\_diffBuf.position(0);
 ByteBuffer msbb
 = ByteBuffer.allocateDirect(mat\_spec.length\*4);
 msbb.order(ByteOrder.nativeOrder());
 FloatBuffer mat\_specBuf = msbb.asFloatBuffer();
 mat\_specBuf.put(mat\_spec);
 mat\_specBuf.position(0);
 gl.glMaterialfv(GL10.GL\_FRONT\_AND\_BACK,
 GL10.GL\_AMBIENT, mat\_ambBuf);
 gl.glMaterialfv(GL10.GL\_FRONT\_AND\_BACK,
 GL10.GL\_DIFFUSE, mat\_diffBuf);
 gl.glMaterialfv(GL10.GL\_FRONT\_AND\_BACK,
 GL10.GL\_SPECULAR, mat\_specBuf);
 gl.glMaterialf(GL10.GL\_FRONT\_AND\_BACK,
 GL10.GL\_SHININESS, 64.0f);
 sphere.draw(gl);
}  

http://wiki.jikexueyuan.com/project/opengl-es-guide/images/104.png" alt="" />

本例下載