Examples of OpenGL rotating triangles

In Android, we use glsurfaceview to display OpenGL views. glsurfaceview is a very important class, which is located in Android. the OpenGL package is used to manage a special surface that can be the memory of a composite view robot system. Manage An EGL display that visualizes OpenGL. Allows a user to provide input render objects for display. A dedicated thread rendering interface is implemented from the UI thread to achieve 3D performance.So here we will first build our own Renderer class,

 
Public class helloopengles10renderer implements glsurfaceview. Renderer {}
 

In the helloopengles10renderer class, three Abstract methods of the Renderer interface must be implemented: ondrawframe, onsurfacechanged, onsurfacecreated

The following is an example:

First, we need to create a glsurfaceview:

 
Class helloopengles10surfaceview extends glsurfaceview {public helloopengles10surfaceview (context) {super (context); setrenderer (New helloopengles10renderer ());}}
 

@ Override public void oncreate (bundle savedinstancestate) {super. oncreate (savedinstancestate); glsurfaceview view = new helloopengles10surfaceview (this); setcontentview (View );}
 

Next, our core class helloopengles10renderer implements the Renderer interface:

Public class helloopengles10renderer implements glsurfaceview. renderer {float rotatetri, rotatequad; private floatbuffer trianglevb; // The four vertices of a square, private floatbuffer quatebuffer; /*** convert the float array and store it in the byte buffer array * @ Param arr * @ return */private void initquate () {float [] Four = {-0.5f,-0.5f, 0.5f, 0.5f,-0.5f, 0.5f,-0.5f, 0.5f, 0.5f, 0.5f, 0.5f, 0.5f,}; bytebuffer vBB = bytebuffer. allocatedirect (// allocate buffer space. A float occupies 4 bytes of four. length * 4); vBB. order (byteorder. nativeorder (); // you can specify byteorder. nativeorder () is to obtain the local byte order quatebuffer = vBB. asfloatbuffer (); // convert to float quatebuffer. put (four); // Add data quatebuffer. position (0); // set the starting position of the array} private void initshapes () {float trianglecoords [] = {// X, Y, Z-0.5f,-0.25f, 0, 0.5f, -0.25f, 0, 0.0f, 0.559016994f, 0}; bytebuffer vBB = bytebuffer. allocatedirect (trianglecoords. length * 4); vBB. order (byteorder. nativeorder (); trianglevb = vBB. asfloatbuffer (); trianglevb. put (trianglecoords); trianglevb. position (0);} public void onsurfacecreated (gl10 GL, eglconfig config) {// set the background color GL. glclearcolor (0.5f, 0.5f, 0.5f, 1.0f); initshapes (); initquate (); GL. glableclientstate (gl10.gl _ vertex_array);} // all plotting operations are performed in this method. Public void ondrawframe (gl10 GL) {// clear the screen and depth cache GL. glclear (gl10.gl _ color_buffer_bit | gl10.gl _ depth_buffer_bit); // switch to the model observation matrix GL. glmatrixmode (gl10.gl _ modelview); // reset the current model observation matrix GL. glloadidentity (); // you can specify the view position. glulookat (GL, 0, 0,-5, 0f, 0f, 0f, 0f, 1.0f, 0.0f); // create a rotating triangle to rotate GL along the Y axis. glrotatef (rotatetri, 0.0f, 1.0f, 0.0f); // draw a triangle // set the current color GL. glcolor4f (0.61161875f, 0.76953125f, 0.22265625f, 0.0f); GL. glvertexpointer (3, gl10.gl _ float, 0, trianglevb); GL. gldrawarrays (gl10.gl _ triangles, 0, 3); // move 1 unit GL along the X axis square. gltranslatef (1.0f, 0.0f, 0.0f); // create a rotated square to rotate GL along the X axis. glrotatef (rotatequad, 1.0f, 0.0f, 0.0f); // draw a square GL. glcolor4f (0.61161875f, 0.76953125f, 0.22265625f, 0.0f); GL. glvertexpointer (3, gl10.gl _ float, 0, quatebuffer); GL. gldrawarrays (gl10.gl _ triangle_strip, 0, 4); // change the Rotation Angle rotatetri + = 0.5f; rotatequad-= 0.5f;} public void onsurfacechanged (gl10 GL, int width, int height) {// set the OpenGL scenario size GL. glviewport (0, 0, width, height); float ratio = (float) width/height; GL. glmatrixmode (gl10.gl _ projection); // sets the projection matrix GL. glloadidentity (); // sets the matrix as the unit matrix, which is equivalent to Resetting the matrix GL. glfrustumf (-ratio, ratio,-1, 1, 3, 7); // apply the projection matrix }}

The above methods are basically commented out, and I believe everyone can understand them,

Finally, let's take a look at the running effect!