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我发现从 opengles 开始真的很难。我在网上到处找教程。找到一本 Philips Rideout 的免费书,尝试了几章,但由于缺乏良好的 C++ 技能,我把它放在了中间。然后尝试了 Ray Wenderlich 的教程,但被着色器卡住了,无法制作一个非常简单的教程。现在,我在 Jeff Lamarche 的旧博客上徘徊。我知道有一个相当不错的面向对象框架,叫做 COCOS2D,它几乎可以完成 2D 游戏和图形所需的一切,但我想在实际尝试 COCOS2D 之前打好基础。但是,似乎我永远也达不到那里。我一个接一个地遇到麻烦,我没有办法找到解决办法。所以,我一次又一次地来堆栈溢出来澄清我的误解。

我对 OpenGLES 中一个非常简单的三角形有疑问。此示例使用 OpenGLES 1.0。在我看来渲染图形的代码是这样的,

struct Vertex3D{
    GLfloat x;
    GLfloat y;
    GLfloat z;

};


struct Triangle3D{
    Vertex3D v1;
    Vertex3D v2;
    Vertex3D v3;

};


static inline Triangle3D Triangle3DMake(Vertex3D vertex1, Vertex3D vertex2, Vertex3D vertex3){
    Triangle3D triangle;
    triangle.v1 = vertex1;
    triangle.v2 = vertex2;
    triangle.v3 = vertex3;
    return triangle;
};

static inline Vertex3D vertex3DMake(GLfloat x, GLfloat y, GLfloat z){
    Vertex3D vertex;
    vertex.x = x;
    vertex.y = y;
    vertex.z = z;
    return vertex;
}


static inline GLfloat Vertex3DCalculateDistanceBetweemVertices(Vertex3D first, Vertex3D second){
    GLfloat deltaX = second.x - first.x;
    GLfloat deltaY = second.y - first.y;
    GLfloat deltaZ = second.z - first.z;
    return sqrtf(powf(deltaX, 2) + powf(deltaY, 2) + powf(deltaZ, 2));
}


@implementation GLView{
    GLuint renderbuffer;
    GLuint framebuffer;
    EAGLContext *_context;
    CAEAGLLayer *layer;
    GLuint depthbuffer;
}

+(Class)layerClass{
    return [CAEAGLLayer class];
}

-(void)setUpLayer{
    layer = (CAEAGLLayer*)super.layer;
}

-(void)setUpContext{
    EAGLRenderingAPI api = kEAGLRenderingAPIOpenGLES1;
    _context = [[EAGLContext alloc] initWithAPI:api];
    if(!_context){
        NSLog(@"Could not create context");
        abort();
    }

    if(![EAGLContext setCurrentContext:_context]){
        NSLog(@"Could not set current context");
        abort();
    }
}

-(void)setUpRenderBuffer{
    glGenRenderbuffersOES(1, &renderbuffer);
    glBindRenderbufferOES(GL_RENDERBUFFER_OES, renderbuffer);

    glGenRenderbuffers(1, &depthbuffer);
    glBindRenderbufferOES(GL_DEPTH_COMPONENT16_OES, depthbuffer);
    [_context renderbufferStorage:GL_RENDERBUFFER_OES fromDrawable:layer];
    [_context renderbufferStorage:GL_DEPTH_COMPONENT16_OES fromDrawable:layer];
}

-(void)setUpFrameBuffer{
    glGenFramebuffersOES(1, &framebuffer);
    glBindFramebufferOES(GL_FRAMEBUFFER_OES, framebuffer);
    glFramebufferRenderbufferOES(GL_FRAMEBUFFER_OES, GL_COLOR_ATTACHMENT0_OES, GL_RENDERBUFFER_OES, renderbuffer);
    glFramebufferRenderbufferOES(GL_FRAMEBUFFER_OES, GL_DEPTH_ATTACHMENT_OES, GL_DEPTH_COMPONENT16_OES, depthbuffer);
}

-(void)render{
    Vertex3D    vertex1 = vertex3DMake(0,1,0);
    Vertex3D    vertex2 = vertex3DMake(1.0, 0.0, 0);
    Vertex3D    vertex3 = vertex3DMake(-1.0, 0.0, 0.);
    Triangle3D  triangle = Triangle3DMake(vertex1, vertex2, vertex3);
    glViewport(0, 0, self.bounds.size.width, self.bounds.size.height);
    glClearColor(0.7, 0.7, 0.7, 1.0);
    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
    glEnableClientState(GL_VERTEX_ARRAY);
    glColor4f(1.0, 0.0, 0.0, 1.0);
    glVertexPointer(3, GL_FLOAT, 0, &triangle);
    glDrawArrays(GL_TRIANGLES, 0, 9);
    [_context presentRenderbuffer:GL_RENDERBUFFER_OES];
    glDisableClientState(GL_VERTEX_ARRAY);


}
- (id)initWithFrame:(CGRect)frame
{
    self = [super initWithFrame:frame];
    if (self) {
        [self setUpLayer];
        [self setUpContext];
        [self setUpRenderBuffer];
        [self setUpFrameBuffer];

        [self render];
    }
    return self;
}

此代码产生的图形如下图所示;

在此处输入图像描述

因为,我使用的是(1,0),(-1,0),(1,0)的二维坐标,所以我假设它应该给我这样的数字;

在此处输入图像描述

我确信我做错了一些非常小的事情。如果有人能指出我,这对我来说将是一个很大的帮助。再次感谢你。

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1 回答 1

2

看起来您只是渲染了太多顶点,而 OpenGL 正在将顶点数组的末尾读取到未初始化的内存中。线

glDrawArrays(GL_TRIANGLES, 0, 9);

应该是

glDrawArrays(GL_TRIANGLES, 0, 3);

如果你只想画一个三角形。第三个参数是要渲染的顶点总数。

于 2013-01-09T21:57:14.527 回答