例如，我有以下代码（例如，我正在构建而不是游戏，我正在尝试通过 OpenGL ES 构建 KNOB 控件，Quartz2D 不适合，不要问为什么）：
代码在屏幕上绘制以下图像，以后我将用我的旋钮替换这些图像：
基本上我只对旋转播放器（左侧区域的人）感兴趣。我希望他从 0 到 360 度连续旋转。我尝试了以下代码，但是...
self.effect.transform.modelviewMatrix = GLKMatrix4Rotate(self.effect.transform.modelviewMatrix, radians(10), 0, 0, -1);
我提供全屏旋转（也有怪物），但我只想旋转一个对象（在这个例子中只有左侧区域的玩家）。还要注意怪物在移动。
函数[sprite render]的代码；见下文。
这是主要代码：
//
// SGGViewController.m
// SimpleGLKitGame
//
// Created by Ray Wenderlich on 1/30/12.
// Copyright (c) 2012 __MyCompanyName__. All rights reserved.
//
#import "SGGViewController.h"
#import "SGGSprite.h"
@interface SGGViewController ()
@property (strong, nonatomic) EAGLContext *context;
@property (strong) GLKBaseEffect * effect;
@property (strong) SGGSprite * player;
@property (strong) NSMutableArray * children;
@property (assign) float timeSinceLastSpawn;
@end
@implementation SGGViewController
@synthesize effect = _effect;
@synthesize context = _context;
@synthesize player = _player;
@synthesize children = _children;
@synthesize timeSinceLastSpawn = _timeSinceLastSpawn;
- (void)viewDidLoad
{
[super viewDidLoad];
self.context = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
if (!self.context) {
NSLog(@"Failed to create ES context");
}
GLKView *view = (GLKView *)self.view;
view.context = self.context;
[EAGLContext setCurrentContext:self.context];
self.effect = [[GLKBaseEffect alloc] init];
GLKMatrix4 projectionMatrix = GLKMatrix4MakeOrtho(0, 1024, 0, 768, -1, 1);
self.effect.transform.projectionMatrix = projectionMatrix;
self.player = [[SGGSprite alloc] initWithFile:@"2.png" effect:self.effect];
self.player.position = GLKVector2Make(self.player.contentSize.width/2, 160);
self.children = [NSMutableArray array];
[self.children addObject:self.player];
}
- (void)addTarget {
SGGSprite * target = [[SGGSprite alloc] initWithFile:@"Target.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;
target.position = GLKVector2Make(480 + (target.contentSize.width/2), actualY);
int minVelocity = 480.0/4.0;
int maxVelocity = 480.0/2.0;
int rangeVelocity = maxVelocity - minVelocity;
int actualVelocity = (arc4random() % rangeVelocity) + minVelocity;
target.moveVelocity = GLKVector2Make(-actualVelocity, 0);
}
- (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation
{
return UIInterfaceOrientationIsLandscape(interfaceOrientation);
}
#pragma mark - GLKViewDelegate
static inline double radians (double degrees) {return degrees * M_PI/180;}
- (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) {
[sprite render];
}
}
- (void)update {
self.timeSinceLastSpawn += self.timeSinceLastUpdate;
if (self.timeSinceLastSpawn > 1.0) {
self.timeSinceLastSpawn = 0;
[self addTarget];
}
for (SGGSprite * sprite in self.children) {
[sprite update:self.timeSinceLastUpdate];
}
}
@end
这是函数 [sprite render] 的代码；
//
// SGGSprite.m
// SimpleGLKitGame
//
// Created by Ray Wenderlich on 1/30/12.
// Copyright (c) 2012 __MyCompanyName__. All rights reserved.
//
#import "SGGSprite.h"
typedef struct {
CGPoint geometryVertex;
CGPoint textureVertex;
} TexturedVertex;
typedef struct {
TexturedVertex bl;
TexturedVertex br;
TexturedVertex tl;
TexturedVertex tr;
} TexturedQuad;
@interface SGGSprite()
@property (strong) GLKBaseEffect * effect;
@property (assign) TexturedQuad quad;
@property (strong) GLKTextureInfo * textureInfo;
@end
@implementation SGGSprite
@synthesize position = _position;
@synthesize contentSize = _contentSize;
@synthesize effect = _effect;
@synthesize quad = _quad;
@synthesize textureInfo = _textureInfo;
@synthesize moveVelocity = _moveVelocity;
- (id)initWithFile:(NSString *)fileName effect:(GLKBaseEffect *)effect {
if ((self = [super init])) {
self.effect = effect;
NSDictionary * options = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithBool:YES],
GLKTextureLoaderOriginBottomLeft,
nil];
NSError * error;
NSString *path = [[NSBundle mainBundle] pathForResource:fileName ofType:nil];
self.textureInfo = [GLKTextureLoader textureWithContentsOfFile:path options:options error:&error];
if (self.textureInfo == nil) {
NSLog(@"Error loading file: %@", [error localizedDescription]);
return nil;
}
self.contentSize = CGSizeMake(self.textureInfo.width, self.textureInfo.height);
TexturedQuad newQuad;
newQuad.bl.geometryVertex = CGPointMake(0, 0);
newQuad.br.geometryVertex = CGPointMake(self.textureInfo.width, 0);
newQuad.tl.geometryVertex = CGPointMake(0, self.textureInfo.height);
newQuad.tr.geometryVertex = CGPointMake(self.textureInfo.width, self.textureInfo.height);
newQuad.bl.textureVertex = CGPointMake(0, 0);
newQuad.br.textureVertex = CGPointMake(1, 0);
newQuad.tl.textureVertex = CGPointMake(0, 1);
newQuad.tr.textureVertex = CGPointMake(1, 1);
self.quad = newQuad;
}
return self;
}
- (GLKMatrix4) modelMatrix {
GLKMatrix4 modelMatrix = GLKMatrix4Identity;
modelMatrix = GLKMatrix4Translate(modelMatrix, self.position.x, self.position.y, 0);
modelMatrix = GLKMatrix4Translate(modelMatrix, -self.contentSize.width/2, -self.contentSize.height/2, 0);
return modelMatrix;
}
static inline double radians (double degrees) {return degrees * M_PI/180;}
- (void)render {
self.effect.texture2d0.name = self.textureInfo.name;
self.effect.texture2d0.enabled = YES;
self.effect.transform.modelviewMatrix = self.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);
}
- (void)update:(float)dt {
GLKVector2 curMove = GLKVector2MultiplyScalar(self.moveVelocity, dt);
self.position = GLKVector2Add(self.position, curMove);
}
@end