c++ opengl es 2.0 - create rectangle and circle

In OpenGL ES 2.0, GL_QUADS and GL_POLYGON is not supported. Also fixed function pipeline is disabled in OpenGL ES 2.0. You need to create a shader program, and attach vertex shader and pixel shader with this program. Then set vertex data to the this program.

Here is a sample code in OpenGLES2.0.

Vertex shader source

// Vertex shader program.
attribute vec4 Position;
attribute vec4 SourceColor;
varying vec4 DestinationColor;

void main(void)
{
    DestinationColor = SourceColor;
    gl_Position = Position;
}

Pixel shader source

// Pixel shader.
varying lowp vec4 DestinationColor;

void main(void)
{
    gl_FragColor = DestinationColor;
}

Setup vertex data

private final float TriangleVerticesData[]                           =
{// X, Y, Z,
-1.0f, -1.0f, 0.0f, 
-1.0f, 1.0f, 0.0f, 
1.0f, -1.0f, 0.0f, 
1.0f, 1.0f, 0.0f,};

ByteBuffer temp     = ByteBuffer.allocateDirect( TriangleVerticesData.length * 4);
temp.order( ByteOrder.nativeOrder());
mTriangleVertices   = temp.asFloatBuffer();
mTriangleVertices.put( TriangleVerticesData ).position( 0 );

Prepare shader program

// Prepare program, vertex and pixel shader setup.
nShaderProgram = GLES20.glCreateProgram();

// Vertex shader
int VSshader = GLES20.glCreateShader( GLES20.GL_VERTEX_SHADER );
GLES20.glShaderSource( VSshader, VSshaderSource);
GLES20.glCompileShader( VSshader );

int compiled[] = new int[1];
            GLES20.glGetShaderiv( shader, GLES20.GL_COMPILE_STATUS, compiled, 0 );
            if ( 0 == compiled[0] ) { // compilation failed.
                GLES20.glDeleteShader( shader );
                shader = 0;
            }

// Pixel shader.
int PSshader = GLES20.glCreateShader( GLES20.GL_PIXEL_SHADER );
GLES20.glShaderSource( VSshader, PSshaderSource);
GLES20.glCompileShader( PSshader );

{
int compiled[] = new int[1];
            GLES20.glGetShaderiv( shader, GLES20.GL_COMPILE_STATUS, compiled, 0 );
            if ( 0 == compiled[0] ) { // compilation failed.
                GLES20.glDeleteShader( shader );
                shader = 0;
            }
}

Bind vertex data and draw quad to screen.

GLES20.glUseProgram( nShaderProgram );
       int nParam = GLES20.glGetAttribLocation( nShaderProgram, "Position" );

       mTriangleVertices.position( 0);
       GLES20.glVertexAttribPointer( nParam, 3, GLES20.GL_FLOAT, false,
                                     4 * sizeof(, // 3 vertices for 4 vertices
                   mTriangleVertices );
       GLES20.glEnableVertexAttribArray( nParam );


           // Draw
           GLES20.glClear( GLES20.GL_COLOR_BUFFER_BIT );
           GLES20.glDrawArrays( GLES20.GL_TRIANGLE_STRIP, 0, 4 );

GL_POLYGON is also allowed in OpenGLES 2.0, therefore you have to prepare equivalent vertex buffers for the POLYGON
object.

Please refer following link for more details.

http://developer.android.com/training/graphics/opengl/draw.html