package com.example.bogdankyuchukov.glexample;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;
import java.nio.ShortBuffer;

import javax.microedition.khronos.opengles.GL10;

/**
 * Created by Bogdan Kyuchukov on 25.10.2016.
 */

public class GLTriangleEx {

    private float vertices[] = {0f, 1f,
                               1f, -1f,
                             -1f, -1f};

    private FloatBuffer verticesBuffer;
    private short[] pointIndex = {0, 1, 2};
    private ShortBuffer pointBuffer;

    public GLTriangleEx()
    {
        ByteBuffer byteBuffer = ByteBuffer.allocateDirect(vertices.length * 4);
        byteBuffer.order(ByteOrder.nativeOrder());
        verticesBuffer = byteBuffer.asFloatBuffer();
        verticesBuffer.put(vertices);
        verticesBuffer.position(0);

        ByteBuffer pointByteBuffer = ByteBuffer.allocateDirect(pointIndex.length * 2);
        pointByteBuffer.order(ByteOrder.nativeOrder());
        pointBuffer = pointByteBuffer.asShortBuffer();
        pointBuffer.put(pointIndex);
        pointBuffer.position(0);
    }

    public void draw(GL10 gl)
    {
        gl.glFrontFace(GL10.GL_CW);
        gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);

        gl.glVertexPointer(2, GL10.GL_FLOAT, 0, verticesBuffer);
        gl.glDrawElements(GL10.GL_TRIANGLES, pointIndex.length, GL10.GL_UNSIGNED_SHORT, pointBuffer);
        gl.glDisableClientState(GL10.GL_VERTEX_ARRAY);
    }
}