public class Star {
 // Our vertices.
 protected float vertices[];
 // Our vertex buffer.
 protected FloatBuffer vertexBuffer;
 public Star() {
 float a=(float)(1.0f/(2.0f-2f\*Math.cos(72f\*Math.PI/180.f)));
 float bx=(float)(a\*Math.cos(18\*Math.PI/180.0f));
 float by=(float)(a\*Math.sin(18\*Math.PI/180f));
 float cy=(float)(-a \* Math.cos(18\*Math.PI/180f));
 vertices=new float[]{
 0,a,0.5f,cy,-bx,by,bx,by,-0.5f,cy
 };
 ByteBuffer vbb
 = ByteBuffer.allocateDirect(vertices.length \* 4);
 vbb.order(ByteOrder.nativeOrder());
 vertexBuffer = vbb.asFloatBuffer();
 vertexBuffer.put(vertices);
 vertexBuffer.position(0);
 }
 /**
 * This function draws our star on screen.
 * @param gl
 */
 public void draw(GL10 gl) {
 // Counter-clockwise winding.
 gl.glFrontFace(GL10.GL\_CCW);
 // Enable face culling.
 gl.glEnable(GL10.GL\_CULL\_FACE);
 // What faces to remove with the face culling.
 gl.glCullFace(GL10.GL\_BACK);
 // Enabled the vertices buffer for writing
 //and to be used during
 // rendering.
 gl.glEnableClientState(GL10.GL\_VERTEX\_ARRAY);
 // Specifies the location and data format of
 //an array of vertex
 // coordinates to use when rendering.
 gl.glVertexPointer(2, GL10.GL\_FLOAT, 0,
 vertexBuffer);
 gl.glDrawArrays(GL10.GL_LINE_LOOP, 0,5);
 // Disable the vertices buffer.
 gl.glDisableClientState(GL10.GL\_VERTEX\_ARRAY);
 // Disable face culling.
 gl.glDisable(GL10.GL\_CULL\_FACE);
 }
}

Star 定義了五角星的五個(gè)頂點(diǎn)，并使用 glDrawArrays 來(lái)繪制五角星，因此 vertices 頂點(diǎn)的順序比較重要。

然后定義一個(gè) DrawSolarSystem 來(lái)繪制這個(gè)迷你太陽(yáng)系：

public class DrawSolarSystem extends OpenGLESActivity
 implements IOpenGLDemo{
 private Star sun=new Star();
 private Star earth=new Star();
 private Star moon=new Star();
 private int angle=0;
 /** Called when the activity is first created. */
 \@Override
 public void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 }
 public void DrawScene(GL10 gl) {
 super.DrawScene(gl);
 gl.glLoadIdentity();
 GLU.gluLookAt(gl,0.0f, 0.0f, 15.0f,
 0.0f, 0.0f, 0.0f,
 0.0f, 1.0f, 0.0f);
 // Star A
 // Save the current matrix.
 gl.glPushMatrix();
 // Rotate Star A counter-clockwise.
 gl.glRotatef(angle, 0, 0, 1);
 gl.glColor4f(1.0f, 0.0f, 0.0f, 1.0f);
 // Draw Star A.
 sun.draw(gl);
 // Restore the last matrix.
 gl.glPopMatrix();
 // Star B
 // Save the current matrix
 gl.glPushMatrix();
 // Rotate Star B before moving it,
 //making it rotate around A.
 gl.glRotatef(-angle, 0, 0, 1);
 // Move Star B.
 gl.glTranslatef(3, 0, 0);
 // Scale it to 50% of Star A
 gl.glScalef(.5f, .5f, .5f);
 gl.glColor4f(0.0f, 0.0f, 1.0f, 1.0f);
 // Draw Star B.
 earth.draw(gl);
 // Star C
 // Save the current matrix
 gl.glPushMatrix();
 // Make the rotation around B
 gl.glRotatef(-angle, 0, 0, 1);
 gl.glTranslatef(2, 0, 0);
 // Scale it to 50% of Star B
 gl.glScalef(.5f, .5f, .5f);
 // Rotate around it's own center.
 gl.glRotatef(angle\*10, 0, 0, 1);
 gl.glColor4f(1.0f, 1.0f, 1.0f, 1.0f);
 // Draw Star C.
 moon.draw(gl);
 // Restore to the matrix as it was before C.
 gl.glPopMatrix();
 // Restore to the matrix as it was before B.
 gl.glPopMatrix();
 // Increse the angle.
 angle++;
 }
}

使用 GLU 的 gluLookAt 來(lái)定義 modelview Matrix ，把相機(jī)放在正對(duì)太陽(yáng)中心(0,0,0)，距離 15 (0,0,15)。

使用 glPushMatrix 和 glPopMatrix 來(lái)將當(dāng)前 Matrix 入?；蚴浅鰲?。

首先將當(dāng)前 matrix 入棧，以紅色繪制太陽(yáng)，并逆向轉(zhuǎn)動(dòng)，將當(dāng)前 matrix 入棧的目的是在能夠在繪制地球時(shí)恢復(fù)當(dāng)前棧。

然后繪制地球，使用局部坐標(biāo)系來(lái)想象地球和太陽(yáng)之間的相對(duì)運(yùn)動(dòng)，地球離開一距離繞太陽(yáng)公轉(zhuǎn)，相當(dāng)于先旋轉(zhuǎn)地球的局部坐標(biāo)系，然后再平移地球的局部坐標(biāo)系。對(duì)應(yīng)到代碼為先 glRotatef ,然后 glTranslate.

最后是繪制月亮，使用類似的空間想象方法。

http://wiki.jikexueyuan.com/project/opengl-es-guide/images/85.png" alt="" />

本例下載

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繪制迷你太陽(yáng)系