OpenGL ES 顶点数组对象和奇怪的伪影

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【中文标题】OpenGL ES 顶点数组对象和奇怪的伪影【英文标题】:OpenGL ES Vertex Array Object and strange artifacts 【发布时间】:2013-11-05 17:33:04 【问题描述】:

我正在渲染一个场景,只要方向发生变化,就必须重建一个场景,以便适当地填充屏幕。场景渲染了一些常规彩色四边形的顶点数组对象和一组纹理顶点数组对象。所有这些绘图元素,包括任何着色器和相关的顶点、索引等数组都包含在一个类中,所以我每次都把这个类吹走,并在旋转时执行一个新的 alloc/init。

第一次创建场景时,一切看起来都很好。然而,由于某种原因并且没有明显的模式,奇怪的三角形可能出现在任何后续的旋转中。对于特定场景,每次加载时的发生似乎都是确定性的。然而,从一个场景到另一个场景,有时会出现人工制品,有时一切看起来都很可爱。

我不知道这是否是我破坏记忆的方式(即使在 ARC 中,我也需要释放其中的一部分),还是我创建 VAO 的方式。但是,由于问题仅在我拆除场景并重建它时才会出现......然后我开始用这个思考过程再次旋转我的***。

我有很多代码,所以这里有一些(希望是)相关代码。

这是彩色四边形 VAO 的一些绘图代码。我正在向 NSMutableArray 添加顶点,因为我不知道会有多少个四边形。

- (void) buildNode : (NSDictionary *) nodeDictionary
            bounds : (BoundsGL) bounds

    if (!nodeDictionary)
    
        return;
    

    NSString *jobidstr = [nodeDictionary objectForKey:kNodeJobidKey];
    NSInteger jobid = jobidstr == NULL ? -1 : [jobidstr intValue];

    NSString *colorHexStr = [nodeDictionary objectForKey:kNodeColorKey];
    ColorGL color = HexidecimalStringToColorGL(colorHexStr);


    //
    // indices

    [_coloredQuadIndices addObject:[NSNumber numberWithInt:_coloredQuadVertices.count]];
    [_coloredQuadIndices addObject:[NSNumber numberWithInt:_coloredQuadVertices.count+1]];
    [_coloredQuadIndices addObject:[NSNumber numberWithInt:_coloredQuadVertices.count+2]];
    [_coloredQuadIndices addObject:[NSNumber numberWithInt:_coloredQuadVertices.count+2]];
    [_coloredQuadIndices addObject:[NSNumber numberWithInt:_coloredQuadVertices.count+1]];
    [_coloredQuadIndices addObject:[NSNumber numberWithInt:_coloredQuadVertices.count+3]];


    //
    // vertices

    GLfloat x2 = bounds.pos.x + bounds.size.w;
    GLfloat y2 = bounds.pos.y + bounds.size.h;

    PointGL blp = bounds.pos.x, bounds.pos.y;
    PointGL brp = x2, bounds.pos.y;
    PointGL tlp = bounds.pos.x, y2;
    PointGL trp = x2, y2;

    ColoredVertex bl =  .pos = blp, .color = color ;
    ColoredVertex br =  .pos = brp, .color = color ;
    ColoredVertex tl =  .pos = tlp, .color = color ;
    ColoredVertex tr =  .pos = trp, .color = color ;

    NSValue *tlv = [NSValue valueWithBytes:&tl objCType:@encode(ColoredVertex)];
    NSValue *blv = [NSValue valueWithBytes:&bl objCType:@encode(ColoredVertex)];
    NSValue *trv = [NSValue valueWithBytes:&tr objCType:@encode(ColoredVertex)];
    NSValue *brv = [NSValue valueWithBytes:&br objCType:@encode(ColoredVertex)];
    [_coloredQuadVertices addObject:tlv];
    [_coloredQuadVertices addObject:blv];
    [_coloredQuadVertices addObject:trv];
    [_coloredQuadVertices addObject:brv];

为纹理四边形创建 VAO 的一些代码:

#import "TexturedQuadVAO.h"
#import "Texture.h"
#import "ShaderUtil.h"

@interface TexturedQuadVAO()

    GLuint _textureUniformLocation;


@property (strong, nonatomic) Texture *texture;

@end


@implementation TexturedQuadVAO

@synthesize vaoid = _vaoid;

@synthesize vertexBuffer = _vertexBuffer;
@synthesize vcount = _vcount;
@synthesize vsize = _vsize;

@synthesize indexBuffer = _indexBuffer;
@synthesize icount = _icount;
@synthesize isize = _isize;

@synthesize texture = _texture;

- (id) initWithData : (TexturedVertex *) vertices
   numberOfVertices : (NSUInteger) vcount
       verticesSize : (size_t) vsize
            indices : (GLushort *) indices
    numberOfIndices : (NSUInteger) icount
        indicesSize : (size_t) isize
           viewSize : (CGSize) viewSize
               text : (NSString *) text
        textureSize : (SizeGL) textureSize
    foregroundColor : (UIColor *) fgcolor
    backgroundColor : (UIColor *) bgcolor
textureUniformLocation : (GLuint) textureUniformLocation

    self = [super init];

    if (self)
    
        //
        // geometry

        self.vcount = vcount;
        self.vsize = vsize;

        self.icount = icount;
        self.isize = isize;


        //
        // texture

        self.texture = [[Texture alloc] init];
        UIFont *font = [UIFont fontWithName:@"Arial" size:24];
        SizeGL tSize = textureSize.w * 2.5, textureSize.h * 2.5;
        UIImage *img = createTextImage(viewSize, text, tSize, font, fgcolor, bgcolor);

        [self.texture setupTextureWithImage:img];


        //
        // for shaders
        _textureUniformLocation = textureUniformLocation;


        [self createVertexArrayObject:vertices indices:indices];
    

    return self;


- (void) createVertexArrayObject : (TexturedVertex *) vertices
                         indices : (GLushort *) indices

    checkGLError(@"  TexturedQuadVAO createVertexArrayObject ");

    // vertex array object

    glGenVertexArraysOES(1, &_vaoid);
    glBindVertexArrayOES(_vaoid);


    //
    // vertices buffer

    GLuint vb;
    glGenBuffers(1, &vb);
    self.vertexBuffer = vb;
    glBindBuffer(GL_ARRAY_BUFFER, self.vertexBuffer);
    glBufferData(GL_ARRAY_BUFFER, self.vsize, vertices, GL_STATIC_DRAW);   // copy data into buffer object

    // position vertex attribute
    glEnableVertexAttribArray(GLKVertexAttribPosition);
    glVertexAttribPointer(GLKVertexAttribPosition, 2, GL_FLOAT, GL_FALSE, sizeof(TexturedVertex), (const GLvoid *) offsetof(TexturedVertex, pos));

    // color vertex attribute
    glEnableVertexAttribArray(GLKVertexAttribColor);
    glVertexAttribPointer(GLKVertexAttribColor, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof(TexturedVertex), (const GLvoid *) offsetof(TexturedVertex, color));

    // textures vertex attribute
    glEnableVertexAttribArray(GLKVertexAttribTexCoord0);
    glVertexAttribPointer(GLKVertexAttribTexCoord0, 2, GL_FLOAT, GL_FALSE, sizeof(TexturedVertex), (const GLvoid  *) offsetof(TexturedVertex, texcoord));


    //
    // index data buffer

    GLuint ib;
    glGenBuffers(1, &ib);
    self.indexBuffer = ib;
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, self.indexBuffer);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, self.isize, indices, GL_STATIC_DRAW); // copy index data into buffer object


    //
    // clear binds

    glBindVertexArrayOES(0);        // ok to unbind for now, and bind when we want to render
    glBindBuffer(GL_ARRAY_BUFFER, 0);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
    checkGLError(@"2 TexturedQuadVAO createVertexArrayObject ");


- (void) render

    checkGLError(@"  TexturedQuadVAO ");

    glBindVertexArrayOES(_vaoid);
    checkGLError(@"2 TexturedQuadVAO ");

    glActiveTexture(GL_TEXTURE0);
    checkGLError(@"3 TexturedQuadVAO ");

    [self.texture bind];
    checkGLError(@"4 TexturedQuadVAO ");

    glUniform1i(_textureUniformLocation, 0);
    checkGLError(@"5 TexturedQuadVAO ");

    //glDrawElements(GL_TRIANGLE_STRIP, self.vsize/sizeof(GLshort), GL_UNSIGNED_SHORT, 0);
    glDrawElements(GL_TRIANGLE_STRIP, self.vsize/sizeof(GLushort), GL_UNSIGNED_SHORT, 0);
    checkGLError(@"6 TexturedQuadVAO ");

    [self.texture unbind];
    checkGLError(@"7 TexturedQuadVAO ");

    glBindVertexArrayOES(0);
    checkGLError(@"8 TexturedQuadVAO ");


- (void) tearDown

    [self.texture deleteTexture];

    glDeleteBuffers(1, &_vertexBuffer);
    glDeleteBuffers(1, &_indexBuffer);
    glDeleteVertexArraysOES(1, &_vaoid);


@end

我的拆解代码:

- (void) tearDown

    // VAOs

    for (int i=0; i<_texturedQuadArray.count; i++)
    
        TexturedVAO *vao = [_texturedQuadArray objectAtIndex:i];
        [vao tearDown];
        vao = nil;
    
    [_texturedQuadArray removeAllObjects];

    if (_coloredQuadVAO)
    
       [_coloredQuadVAO tearDown];
       _coloredQuadVAO = nil;
    

    if (_coloredQuadOutlinesVAO)
    
       [_coloredQuadOutlinesVAO tearDown];
       _coloredQuadOutlinesVAO = nil;
    

    // shaders

    if (_shaders.colorShader)
    
       glDeleteProgram(_shaders.colorShader);
       _shaders.colorShader = 0;
    

    if (_shaders.textureShader)
    
       glDeleteProgram(_shaders.textureShader);
       _shaders.textureShader = 0;
    

    checkGLError(@"Main tearDown");

在过去的几天里,我在网上搜索并尝试了我能想到的一切来找出这个问题,但它开始变得非常糟糕。任何想法将不胜感激!

更新:我发现了问题!

正如我所怀疑的那样,我花了这么多天试图找到的东西非常微不足道 - 在所有错误的地方!

罪魁祸首是这一行:

glDrawElements(GL_TRIANGLE_STRIP, self.vsize/sizeof(GLushort), GL_UNSIGNED_SHORT, 0);

在我注意到这个混乱的计算并立即将其更改为:

glDrawElements(GL_TRIANGLE_STRIP, self.icount, GL_UNSIGNED_SHORT, 0);

即我改为按实际指数计数。

【问题讨论】:

所以现在一切看起来都很好,因为流数据已经改变了场景。几乎就好像四边形的位置与出现的伪影有关,但是我在不同区域使用不同的四边形进行了测试 - 没有任何乐趣。 【参考方案1】:

正如我所想的那样,我花了这么多天时间试图找到的东西非常微不足道 - 在所有错误的地方!

罪魁祸首是 TexturedQuadVAO 的第二组代码中的这一行:

glDrawElements(GL_TRIANGLE_STRIP, self.vsize/sizeof(GLushort), GL_UNSIGNED_SHORT, 0);

在我注意到这个混乱的计算并立即将其更改为:

glDrawElements(GL_TRIANGLE_STRIP, self.icount, GL_UNSIGNED_SHORT, 0);

即我改为按实际指数计数。

【讨论】:

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