Color each vertex.</LI> </HEAD> <BODY> <H1>Color each vertex.</H1> <H2>Create the project</H2> <P> Choose the “OpenGL ES Application” template for your project. Do not remove the <CODE>MainWindow.xib</CODE> file from the project. In the method <CODE><A HREF = "https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIApplicationDelegate_Protocol/Reference/Reference.html#//apple_ref/occ/intfm/UIApplicationDelegate/applicationDidFinishLaunching:">applicationDidFinishLaunching:</A></CODE> in the file <CODE>TriangleAppDelegate.m</CODE>, comment out the call to <CODE>startAnimation</CODE> and insert the following statement. <PRE> [<A HREF = "https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIApplication_Class/Reference/Reference.html">UIApplication</A> <A HREF = "https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIApplication_Class/Reference/Reference.html#//apple_ref/occ/clm/UIApplication/sharedApplication">sharedApplication</A>].<A HREF = "https://developer.apple.com/library/ios/documentation/UIKit/Reference/UIApplication_Class/Reference/Reference.html#//apple_ref/occ/instp/UIApplication/statusBarHidden">statusBarHidden</A> = <A HREF = "https://developer.apple.com/libary/ios/documentation/Cocoa/Reference/ObjCRuntimeRef/Reference/reference.html#//apple_ref/doc/c_ref/YES">YES</A>; </PRE> In the file <CODE>EAGLView.m</CODE>, change the macro <CODE>USE_DEPTH_BUFFER</CODE> from 0 to 1. Replace the <CODE>drawView</CODE> method with the following. </P> <PRE> #define COORDINATES_PER_VERTEX 3 typedef GLfloat vertex_t[COORDINATES_PER_VERTEX]; #define VERTICES_PER_TRIANGLE 3 typedef vertex_t triangle_t[VERTICES_PER_TRIANGLE]; typedef GLfloat color_t[4]; //red, green, blue, alpha //Convert degrees to radians. #define RADIANS(degrees) ((degrees) * M_PI / 180.0) - (void) drawView { [EAGLContext setCurrentContext: context]; glBindFramebufferOES(GL_FRAMEBUFFER_OES, viewFramebuffer); glEnable(GL_DEPTH_TEST); glMatrixMode(GL_PROJECTION); glLoadIdentity(); GLfloat near = .01; //distance from viewer to near surface of frustum GLfloat length = near * tan(RADIANS(45) / 2.0);//45 degree field of view GLfloat ratio = self.bounds.size.height / self.bounds.size.width; glFrustumf( -length, //left length, //right -length * ratio, //bottom length * ratio, //top near, //near 10.0 //far ); glViewport(0, 0, backingWidth, backingHeight); glMatrixMode(GL_MODELVIEW); glClearColor(0.5, 0.5, 0.5, 1.0); //gray background glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glEnableClientState(GL_VERTEX_ARRAY); glEnableClientState(GL_COLOR_ARRAY); //The three coordinates of a vertex at distance 1 from the origin. #define V(theta) {cos(RADIANS(theta)), sin(RADIANS(theta)), 0.0} const triangle_t triangle = { V(90.0 + 0.0 * 120.0), V(90.0 + 1.0 * 120.0), V(90.0 + 2.0 * 120.0) }; static const color_t color[] = { {1.0, 0.0, 0.0, 1.0}, {0.0, 1.0, 0.0, 1.0}, {0.0, 0.0, 1.0, 1.0} }; glTranslatef(0.0, 0.0, -3.0); glVertexPointer(COORDINATES_PER_VERTEX, GL_FLOAT, 0, &triangle); glColorPointer(4, GL_FLOAT, 0, color); glDrawArrays(GL_TRIANGLES, 0, VERTICES_PER_TRIANGLE); glDisableClientState(GL_COLOR_ARRAY); glDisableClientState(GL_VERTEX_ARRAY); glBindRenderbufferOES(GL_RENDERBUFFER_OES, viewRenderbuffer); [context presentRenderbuffer: GL_RENDERBUFFER_OES]; } </PRE> <IMG WIDTH = 320 HEIGHT = 480 SRC = "color.png"> <H2>Things to try</H2> <OL> <LI>Make all three vertices the same color.</LI> </OL> </BODY> </HTML>