1: Intro
In this article/tutorial I ll present how to create *cough* simple *cough* – well simple after you make it, cube with shadow effect. The idea is to make our android based device to display cube that will rotate around it own and – well that happened without my intention – around light source. Problems I meet ware mostly based on me being not familiar with GL API.. but.. one step at time.. in next post I ll present how to add bitmap on the surface of cube..
2: Cube class
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 | package mobile.napier; import java.nio.ByteBuffer; import java.nio.ByteOrder; import java.nio.IntBuffer; import javax.microedition.khronos.opengles.GL10; /** * A vertex shaded cube. */ class Cube { public Cube() { int one = 0x10000; int vertices[] = { -one, -one, -one, one, -one, -one, one, one, -one, -one, one, -one, -one, -one, one, one, -one, one, one, one, one, -one, one, one, }; int colors[] = { 0, 0, 0, one, one, 0, 0, one, one, one, 0, one, 0, one, 0, one, 0, 0, one, one, one, 0, one, one, one, one, one, one, 0, one, one, one, }; byte indices[] = { 0, 4, 5, 0, 5, 1, 1, 5, 6, 1, 6, 2, 2, 6, 7, 2, 7, 3, 3, 7, 4, 3, 4, 0, 4, 7, 6, 4, 6, 5, 3, 0, 1, 3, 1, 2 }; //Buffers ByteBuffer vbb = ByteBuffer.allocateDirect(vertices.length*4); vbb.order(ByteOrder.nativeOrder()); mVertexBuffer = vbb.asIntBuffer(); mVertexBuffer.put(vertices); mVertexBuffer.position(0); ByteBuffer cbb = ByteBuffer.allocateDirect(colors.length*4); cbb.order(ByteOrder.nativeOrder()); mColorBuffer = cbb.asIntBuffer(); mColorBuffer.put(colors); mColorBuffer.position(0); mIndexBuffer = ByteBuffer.allocateDirect(indices.length); mIndexBuffer.put(indices); mIndexBuffer.position(0); } public void draw(GL10 gl) { gl.glFrontFace(gl.GL_CW); gl.glVertexPointer(3, gl.GL_FIXED, 0, mVertexBuffer); gl.glColorPointer(4, gl.GL_FIXED, 0, mColorBuffer); gl.glDrawElements(gl.GL_TRIANGLES, 36, gl.GL_UNSIGNED_BYTE, mIndexBuffer); } private IntBuffer mVertexBuffer; private IntBuffer mColorBuffer; private ByteBuffer mIndexBuffer; } |
I have found this class online but not sure where so there will be no link.. if the owner wants.. drop me an email. 🙂
3: Below Renderer for Cube class
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 | package mobile.napier; import javax.microedition.khronos.egl.EGL10; import javax.microedition.khronos.egl.EGLConfig; import javax.microedition.khronos.opengles.GL10; import android.opengl.GLSurfaceView.Renderer; public class CubeRenderer implements Renderer { public CubeRenderer(boolean useTranslucentBackground) { mTranslucentBackground = useTranslucentBackground; mCube = new Cube(); } @Override public void onDrawFrame(GL10 gl) { // TODO Auto-generated method stub /* * Usually, the first thing one might want to do is to clear * the screen. The most efficient way of doing this is to use * glClear(). */ gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT); /* * Now we're ready to draw some 3D object */ gl.glMatrixMode(GL10.GL_MODELVIEW); gl.glLoadIdentity(); gl.glTranslatef(0, 0, -3.0f); gl.glRotatef(mAngle, 0, 1, 0); gl.glRotatef(mAngle*0.25f, 1, 0, 0); gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); gl.glEnableClientState(GL10.GL_COLOR_ARRAY); mCube.draw(gl); mAngle += 1.2f; } public void onSurfaceChanged(GL10 gl, int width, int height) { gl.glViewport(0, 0, width, height); /* * Set our projection matrix. This doesn't have to be done * each time we draw, but usually a new projection needs to * be set when the viewport is resized. */ float ratio = (float) width / height; gl.glMatrixMode(GL10.GL_PROJECTION); gl.glLoadIdentity(); gl.glFrustumf(-ratio, ratio, -1, 1, 1, 10); } public void onSurfaceCreated(GL10 gl, EGLConfig config) { /* * By default, OpenGL enables features that improve quality * but reduce performance. One might want to tweak that * especially on software renderer. */ gl.glDisable(GL10.GL_DITHER); /* * Some one-time OpenGL initialization can be made here * probably based on features of this particular context */ gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_FASTEST); //lights on! gl.glEnable(GL10.GL_LIGHTING); gl.glEnable(GL10.GL_LIGHT0); float lightAmbient[] = new float[] { 0.2f, 0.3f, 0.6f, 1.0f }; gl.glLightfv(GL10.GL_LIGHT0, GL10.GL_AMBIENT, lightAmbient, 0); // position float[] light0Position = new float[] { 0, 0, 3, 1 }; gl.glLightfv(GL10.GL_LIGHT0, GL10.GL_POSITION, light0Position, 0); gl.glLightfv(GL10.GL_LIGHT0, GL10.GL_AMBIENT, lightAmbient, 0); gl.glLightfv(GL10.GL_LIGHT0, GL10.GL_POSITION, light0Position, 0); gl.glEnable(GL10.GL_DEPTH_TEST); gl.glDepthFunc(GL10.GL_LEQUAL); gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); gl.glClearColor(0.0f, 0.0f, 0.0f, 1.0f); gl.glClearDepthf(1.0f); gl.glEnable(GL10.GL_CULL_FACE); gl.glShadeModel(GL10.GL_SMOOTH); gl.glClearStencil(0); gl.glClearStencil(0); } private boolean mTranslucentBackground; private Cube mCube; private float mAngle; } |
4: Notes
I had a problem with this lines:
1 2 3 4 5 | float lightAmbient[] = new float[] { 0.2f, 0.3f, 0.6f, 1.0f }; gl.glLightfv(GL10.GL_LIGHT0, GL10.GL_AMBIENT, lightAmbient, 0); // position float[] light0Position = new float[] { 0, 0, 3, 1 }; gl.glLightfv(GL10.GL_LIGHT0, GL10.GL_POSITION, light0Position, 0); |
In many tutorials they were using GLfloat and for some reason my eclipse was throwing out some weird errors that I cannot use it.. need to find a reason why that is happening.. anyway.. easy fix.. use floats!
now one global variable
1 | private GLSurfaceView mGLSurfaceView; |
5: Main Class
and one small change for main class
1 2 3 4 5 6 7 8 9 | @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); mGLSurfaceView = new GLSurfaceView(this); mGLSurfaceView.setRenderer(new CubeRenderer(false)); setContentView(mGLSurfaceView); } |
to use GLSurfaceView instead of standard.
I hope it will help someone to save a couple hours of struggling with code,