如何在OpenGLES中的球运动中画一条线？

目前我在iphone上使用OpenGLES进行球类游戏的应用，使用GL_TRIANGLE_STRIP从左到右画球和移动动作，然后GL_LINES画出一条线，但是画线内部不能画球运动，怎么解决呢？

我试过的示例代码：

#1 - (void)update { self.timeSinceLastSpawn += self.timeSinceLastUpdate; self.timeSinceLastSpawn = 0; if (self.timeSinceLastSpawn > 2.0) { [self target]; // Call the Method target } for (SGGSprite * sprite in self.children) //SGGSprite is a class { [sprite update:self.timeSinceLastUpdate]; // call the update method in SGGSprite class. } } #2 - (void)update:(float)dt { GLKVector2 curMove = GLKVector2MultiplyScalar(self.moveVelocity, dt); self.position = GLKVector2Add(self.position, curMove); } #3 - (void)target { SGGSprite * target = [[SGGSprite alloc] initWithFile:@"Ballimage.png" effect:self.effect]; [self.children addObject:target]; int minY = target.contentSize.height/2; int maxY = 320 - target.contentSize.height/2; int rangeY = maxY - minY; int actualY = (arc4random() % rangeY) + minY; if(actualY <= 100) { actualY = 215; } target.position = GLKVector2Make(480 + (target.contentSize.width), actualY); int minVelocity = 480.0/12.0; int maxVelocity = 480.0/6.0; int rangeVelocity = maxVelocity - minVelocity; int actualVelocity = (arc4random() % rangeVelocity) + minVelocity; target.moveVelocity = GLKVector2Make(-actualVelocity, 0); } #4 - (void)glkView:(GLKView *)view drawInRect:(CGRect)rect { glClearColor(1, 1, 1, 1); glClear(GL_COLOR_BUFFER_BIT); glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); glEnable(GL_BLEND); for (SGGSprite * sprite in self.children) // SGGSprite is a class, render method in SGGSprite class { [sprite render]; } } #5 - (void)render { self.effect.texture2d0.name = self.textureInfo.name; self.effect.texture2d0.enabled = YES; self.effect.transform.modelviewMatrix = self.modelMatrix; // Call the method modelMatrix [self.effect prepareToDraw]; long offset = (long)&_quad; glEnableVertexAttribArray(GLKVertexAttribPosition); glEnableVertexAttribArray(GLKVertexAttribTexCoord0); glVertexAttribPointer(GLKVertexAttribPosition, 2, GL_FLOAT, GL_FALSE, sizeof(TexturedVertex), (void *) (offset + offsetof(TexturedVertex, geometryVertex))); glVertexAttribPointer(GLKVertexAttribTexCoord0, 2, GL_FLOAT, GL_FALSE, sizeof(TexturedVertex), (void *) (offset + offsetof(TexturedVertex, textureVertex))); glDrawArrays(GL_TRIANGLE_STRIP, 0, 4); } #6 - (GLKMatrix4) modelMatrix { GLKMatrix4 modelMatrix = GLKMatrix4Identity; modelMatrix = GLKMatrix4Translate(modelMatrix, -self.position.x, -self.position.y, 0); modelMatrix = GLKMatrix4Translate(modelMatrix, self.contentSize.width, self.contentSize.height+140, 0); return modelMatrix; } // To draw a line, when the user tab on a screen. -(void) touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { UITouch *touch = [[event allTouches] anyObject]; CGPoint location = [touch locationInView:touch.view]; float xPosition = location.x; float yPosition = location.y; X = xPosition/50; resultX = X - 4.8; Y = yPosition/61.538461538461538; resultY = Y - 3.2; self.effect = [[GLKBaseEffect alloc] init]; [self.effect prepareToDraw]; Test1 = YES; const GLfloat line[] = { 0.0f, 0.5f, resultX, resultY, }; // Create buffer object array GLuint bufferObjectNameArray; // Have OpenGL generate a buffer name and store the buffer object array glGenBuffers(1, &bufferObjectNameArray); // Bind the buffer object array to the GL_ARRAY_BUFFER target buffer glBindBuffer(GL_ARRAY_BUFFER, bufferObjectNameArray); // Send the line data over to the target buffer glBufferData( GL_ARRAY_BUFFER, // the target buffer sizeof(line), // the number of bytes to put into the buffer line, // a pointer to the data being copied GL_STATIC_DRAW); // the usage pattern of the data // Enable vertex data to be fed down the graphics pipeline to be drawn glEnableVertexAttribArray(GLKVertexAttribPosition); // Specify how the GPU looks up the data glVertexAttribPointer( GLKVertexAttribPosition, // the currently bound buffer holds the data 2, // number of coordinates per vertex GL_FLOAT, // the data type of each component GL_FALSE, // can the data be scaled 2*4, // how many bytes per vertex (2 floats per vertex) NULL); glDrawArrays(GL_LINES, 0, 2); }