在Swift中调用glDrawElements而在Objective-C中调用时,OpenGL EXC_BAD_ACCESS

我正在研究Ray Wenderlich 的OpenGL for iOS教程,试图将他的代码从Objective-C转换为Swift.

我是OpenGL和Swift的新手,并且相信我的问题与我如何翻译Objective-C有关.原因如下:

在我的swift文件中设置包含OpenGL内容的视图,在最后的逻辑步骤(调用glDrawElements)上,应用程序将因EXC_BAD_ACCESS警报而崩溃.但是,如果我将此部分代码移动到Objective-C文件,则应用程序将按预期工作.

Swift版本的代码:

var positionDataOffset: Int = 0
glVertexAttribPointer(self.positionSlot, 3 as GLint, GL_FLOAT.asUnsigned(), 
    GLboolean.convertFromIntegerLiteral(UInt8(GL_FALSE)), 
    VertexDataSource.sizeOfVertex(), &positionDataOffset)

var colorDataOffset = (sizeof(Float) * 3) as AnyObject
glVertexAttribPointer(self.positionSlot, 4 as GLint, GL_FLOAT.asUnsigned(), 
    GLboolean.convertFromIntegerLiteral(UInt8(GL_FALSE)), 
    VertexDataSource.sizeOfVertex(), VertexDataSource.vertexBufferOffset())

var vertexOffset: Int = 0
glDrawElements(GL_TRIANGLES.asUnsigned(), VertexDataSource.vertexCount(),
    GL_UNSIGNED_BYTE.asUnsigned(), &vertexOffset)

这是Objective-C版本:

glVertexAttribPointer(position, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex), 0);
glVertexAttribPointer(color, 4, GL_FLOAT, GL_FALSE, sizeof(Vertex), 
    (GLvoid*) (sizeof(float) * 3));

glDrawElements(GL_TRIANGLES, sizeof(Indices)/sizeof(Indices[0]), GL_UNSIGNED_BYTE, 0);

正如你所看到的,Swift更加冗长......我和其他人一样都是新手.:)

另一个注意事项:在Swift版本中,您将看到对类的几个类方法的调用VertexDataSource.从本质上讲,我无法决定如何将Objective-C的某些部分转换为swift,因此决定(现在)在Objective-C中创建一个可以为Swift代码提供这些属性的小类.以下是Objective-C中的那些方法:

+ (GLint)sizeOfVertex {
    return sizeof(Vertex);
}

+ (GLint)sizeOfIndices {
    return sizeof(Indices);
}

+ (GLint)sizeOfIndicesAtPositionZero {
    return sizeof(Indices[0]);
}

+ (GLint)sizeOfVertices {
    return sizeof(Vertices);
}

+ (GLvoid *)vertexBufferOffset {
    return (GLvoid *)(sizeof(float) * 3);
}

+ (GLint)vertexCount {
    return self.sizeOfIndices / sizeof(GLubyte);
}

将这些行转换为Swift的任何帮助都会令人惊叹.

编辑#1

正如Reto Koradi指出的那样,上面的Swift代码引用了self.positionSlot两次而不是使用colorSlot.这是我在这里发布代码时犯的错误,而不是我的代码中的错误.

所以问题依然存在.

更新了Swift:

var positionDataOffset: Int = 0
glVertexAttribPointer(self.positionSlot, 3 as GLint, GL_FLOAT.asUnsigned(),
    GLboolean.convertFromIntegerLiteral(UInt8(GL_FALSE)),
    VertexDataSource.sizeOfVertex(), &positionDataOffset)
var colorDataOffset = (sizeof(Float) * 3) as AnyObject
glVertexAttribPointer(self.colorSlot, 4 as GLint, GL_FLOAT.asUnsigned(), 
    GLboolean.convertFromIntegerLiteral(UInt8(GL_FALSE)), 
    VertexDataSource.sizeOfVertex(), VertexDataSource.vertexBufferOffset())

var vertexOffset: Int = 0
glDrawElements(GL_TRIANGLES.asUnsigned(), VertexDataSource.vertexCount(), 
    GL_UNSIGNED_BYTE.asUnsigned(), &vertexOffset)

编辑#2:解决了

我最终解决了这个问题.我的问题是在几种情况下我将Objective-C转换为Swift是不正确的.为简洁起见,我将为我最初关注的部分发布Swift代码的最终版本,但是您可以在此示例GitHub repo中查看工作结果的完整源代码.

最终的Swift代码:

let positionSlotFirstComponent: CConstVoidPointer = COpaquePointer(UnsafePointer(0))
glVertexAttribPointer(self.positionSlot, 3 as GLint, GL_FLOAT.asUnsigned(), 
    GLboolean.convertFromIntegerLiteral(UInt8(GL_FALSE)), Int32(sizeof(Vertex)), 
    positionSlotFirstComponent)
let colorSlotFirstComponent: CConstVoidPointer = COpaquePointer(UnsafePointer(sizeof(Float) * 3))
glVertexAttribPointer(self.colorSlot, 4 as GLint, GL_FLOAT.asUnsigned(),
    GLboolean.convertFromIntegerLiteral(UInt8(GL_FALSE)), Int32(sizeof(Vertex)), 
    colorSlotFirstComponent)


let vertextBufferOffset: CConstVoidPointer = COpaquePointer(UnsafePointer(0))
glDrawElements(GL_TRIANGLES.asUnsigned(), Int32(GLfloat(sizeofValue(Indices)) / 
    GLfloat(sizeofValue(Indices.0))), GL_UNSIGNED_BYTE.asUnsigned(), vertextBufferOffset)

我将继续接受Reto Koradi的回答,因为它确实让我走上正轨.