draw OpenGL Circle - Android android.opengl

Android examples for android.opengl:OpenGL

  1. HOME
  2. Android
  3. android.opengl
  4. OpenGL

Description

draw OpenGL Circle

Demo Code


//package com.java2s;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;
import java.util.Hashtable;
import javax.microedition.khronos.opengles.GL10;

public class Main {
    private static Hashtable<Integer, float[]> verticesPool = new Hashtable<Integer, float[]>();
    private static Hashtable<Integer, FloatBuffer> polygonVerticesPool = new Hashtable<Integer, FloatBuffer>();

    public static final void drawCircle(GL10 gl, float x, float y,
            int divides, float radius, float r, float g, float b, float a) {

        float[] vertices = getVertices(divides * 3 * 2);

        int vertexId = 0; 
        for (int i = 0; i < divides; i++) {
       /*www  .ja  v  a2 s  . c  o m*/
            float theta1 = 2.0f / (float) divides * (float) i
                    * (float) Math.PI;
    
            float theta2 = 2.0f / (float) divides * (float) (i + 1)
                    * (float) Math.PI;


            vertices[vertexId++] = x;
            vertices[vertexId++] = y;


            vertices[vertexId++] = (float) Math.cos((double) theta1)
                    * radius + x; // xW
            vertices[vertexId++] = (float) Math.sin((double) theta1)
                    * radius + y; // yW

            // iOp`2_Zbgi~i+1_j
            vertices[vertexId++] = (float) Math.cos((double) theta2)
                    * radius + x; // xW
            vertices[vertexId++] = (float) Math.sin((double) theta2)
                    * radius + y; // yW
        }
        FloatBuffer polygonVertices = makeVerticesBuffer(vertices);

        // |SFw
        gl.glColor4f(r, g, b, a);
        gl.glDisableClientState(GL10.GL_COLOR_ARRAY);

        gl.glVertexPointer(2, GL10.GL_FLOAT, 0, polygonVertices);
        gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);

        gl.glDrawArrays(GL10.GL_TRIANGLES, 0, divides * 3);
    }

    public static float[] getVertices(int n) {
        if (verticesPool.containsKey(n)) {

            return verticesPool.get(n);
        }
        // p\zAnbVe[u
        float[] vertices = new float[n];
        verticesPool.put(n, vertices);
        // g
        return vertices;
    }

    public static final FloatBuffer makeVerticesBuffer(float[] arr) {
        FloatBuffer fb = null;
        if (polygonVerticesPool.containsKey(arr.length)) {
            fb = polygonVerticesPool.get(arr.length);
            fb.clear();
            fb.put(arr);
            fb.position(0);
            return fb;
        }
        fb = makeFloatBuffer(arr);
        polygonVerticesPool.put(arr.length, fb);
        return fb;
    }

    public static final FloatBuffer makeFloatBuffer(float[] arr) {
        ByteBuffer bb = ByteBuffer.allocateDirect(arr.length * 4);
        bb.order(ByteOrder.nativeOrder());
        FloatBuffer fb = bb.asFloatBuffer();
        fb.put(arr);
        fb.position(0);
        return fb;
    }
}

Related Tutorials