Sphere.java

package com.android.droidgraph.primitive;

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

import javax.microedition.khronos.opengles.GL10;

import com.android.droidgraph.shape.GLShape;

public class Sphere extends GLShape {

	@Override
	public void loadGLTexture() {
		// TODO Auto-generated method stub

	}

	FloatBuffer strip, fan_top, fan_bottom;
	float radius;
	int stacks, slices;

	public Sphere(int stacks, int slices, float radius) {
		this.stacks = stacks;
		this.slices = slices;
		this.radius = radius;
		unitSphere(stacks, slices);
	}

	public void draw(GL10 gl) {
//		draw(GL10.GL_TRIANGLE_FAN, gl);
		draw(GL10.GL_LINE_LOOP, gl);
	}

	public void draw(int mode, GL10 gl) {
		if (mode == GL10.GL_LINE_LOOP) {
			gl.glColor4f(1, 0, 0, 1);
		}
		gl.glVertexPointer(3, GL10.GL_FLOAT, 0, fan_top);
		gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);

		gl.glNormalPointer(GL10.GL_FLOAT, 0, fan_top);
		gl.glEnableClientState(GL10.GL_NORMAL_ARRAY);
		gl.glDrawArrays(mode, 0, slices + 2);

		gl.glVertexPointer(3, GL10.GL_FLOAT, 0, strip);
		gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);

		gl.glNormalPointer(GL10.GL_FLOAT, 0, strip);
		gl.glEnableClientState(GL10.GL_NORMAL_ARRAY);
		gl.glDrawArrays(mode, 0, (slices + 1) * 2 * stacks);

		gl.glVertexPointer(3, GL10.GL_FLOAT, 0, fan_bottom);
		gl.glEnableClientState(GL10.GL_VERTEX_ARRAY);

		gl.glNormalPointer(GL10.GL_FLOAT, 0, fan_bottom);
		gl.glEnableClientState(GL10.GL_NORMAL_ARRAY);
		gl.glDrawArrays(mode, 0, slices + 2);
	}

	protected FloatBuffer makeEndCap(int stacks, int slices, boolean top) {
		// Calculate the Triangle Fan for the endcaps
		int triangleFanVertexCount = slices + 2;
		float dtheta = (float) (2.0 * Math.PI / slices);
		float drho = (float) (Math.PI / stacks);
		float[] fanVertices = new float[triangleFanVertexCount * 3];
		float theta = 0;
		float sin_drho = (float) Math.sin(drho);
		// float cos_drho = (float)Math.cos(Math.PI / stacks);
		int index = 0;
		fanVertices[index++] = 0.0f;
		fanVertices[index++] = 0.0f;
		fanVertices[index++] = (top ? 1 : -1);
		for (int j = 0; j <= slices; j++) {
			theta = (j == slices) ? 0.0f : j * (top ? 1 : -1) * dtheta;
			float x = (float) -Math.sin(theta) * sin_drho;
			float y = (float) Math.cos(theta) * sin_drho;
			float z = (top ? 1 : -1) * (float) Math.cos(drho);
			fanVertices[index++] = x;
			fanVertices[index++] = y;
			fanVertices[index++] = z;

		}

		return makeFloatBuffer(fanVertices);
	}

	protected void unitSphere(int stacks, int slices) {
		float drho = (float) (Math.PI / stacks);
		float dtheta = (float) (2.0 * Math.PI / slices);

		fan_top = makeEndCap(stacks, slices, true);
		fan_bottom = makeEndCap(stacks, slices, false);

		// Calculate the triangle strip for the sphere body
		int triangleStripVertexCount = (slices + 1) * 2 * stacks;
		float[] stripVertices = new float[triangleStripVertexCount * 3];

		int index = 0;
		for (int i = 0; i < stacks; i++) {
			float rho = i * drho;

			for (int j = 0; j <= slices; j++) {
				float theta = (j == slices) ? 0.0f : j * dtheta;
				float x = (float) (-Math.sin(theta) * Math.sin(rho));
				float y = (float) (Math.cos(theta) * Math.sin(rho));
				float z = (float) Math.cos(rho);
				// TODO: Implement texture mapping if texture used
				// TXTR_COORD(s, t);
				stripVertices[index++] = x;
				stripVertices[index++] = y;
				stripVertices[index++] = z;

				x = (float) (-Math.sin(theta) * Math.sin(rho + drho));
				y = (float) (Math.cos(theta) * Math.sin(rho + drho));
				z = (float) Math.cos(rho + drho);
				// TODO: Implement texture mapping if texture used
				// TXTR_COORD(s, t);
				stripVertices[index++] = x;
				stripVertices[index++] = y;
				stripVertices[index++] = z;
			}
		}
		strip = makeFloatBuffer(stripVertices);
	}

	/**
	 * Make a direct NIO FloatBuffer from an array of floats
	 * 
	 * @param arr
	 *            The array
	 * @return The newly created FloatBuffer
	 */
	protected 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;
	}

	@Override
	public FloatBuffer getTextureBuffer() {
		// TODO Auto-generated method stub
		return null;
	}

}