关于 ios:Swift: glDrawElements 因 EXC_BAD_ACCESS 代码=1 而崩溃

Swift: glDrawElements crashing with EXC_BAD_ACCESS code=1

我正在通过本指南在 iOS 上学习 OpenGL，我想在 swift 上实现所有内容。所以，有一些代码让我崩溃了：

内存结构：

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private struct Vertex {
var Position: (GLfloat, GLfloat, GLfloat)
var Color: (GLfloat, GLfloat, GLfloat, GLfloat)
}

private static var Vertices = [
Vertex(Position: (1, -1, 0) , Color: (1, 0, 0, 1)),
Vertex(Position: (1, 1, 0) , Color: (0, 1, 0, 1)),
Vertex(Position: (-1, 1, 0) , Color: (0, 0, 1, 1)),
Vertex(Position: (-1, -1, 0), Color: (0, 0, 0, 1))
]

private static var Indices: [GLubyte] = [
0, 1, 2,
2, 3, 0
]

创建顶点缓冲区：

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var vertexBuffer = GLuint()
glGenBuffers(1, &vertexBuffer)
glBindBuffer(GLenum(GL_ARRAY_BUFFER), vertexBuffer)
glBufferData(GLenum(GL_ARRAY_BUFFER), Vertices.size, Vertices, GLenum(GL_STATIC_DRAW))

var indexBuffer = GLuint()
glGenBuffers(1, &indexBuffer)
glBindBuffer(GLenum(GL_ELEMENT_ARRAY_BUFFER), indexBuffer)
glBufferData(GLenum(GL_ELEMENT_ARRAY_BUFFER), Indices.size, Indices, GLenum(GL_STATIC_DRAW))

设置内存偏移：

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var positionPtr = 0
glVertexAttribPointer(GLuint(positionSlot), 3, GLenum(GL_FLOAT), GLboolean(GL_FALSE), GLsizei(strideofValue(Vertex)), &positionPtr)
var colorPtr = strideof(GLfloat) * 3
glVertexAttribPointer(GLuint(colorSlot), 4, GLenum(GL_FLOAT), GLboolean(GL_FALSE), GLsizei(strideofValue(Vertex)), &colorPtr)

崩溃(尝试绘制)：

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var startPtr = 0
// EXC_BAD_ACCESS code=1 here!
glDrawElements(GLenum(GL_TRIANGLES), GLsizei(Indices.count / 3), GLenum(GL_UNSIGNED_BYTE), &startPtr)

所有着色器都编译没有任何错误并且 glClear() 绘制良好，所以我想我的问题与 VBO 有关。

这里我如何计算数组的大小：

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extension Array
{
var size: Int {
get { return self.count * strideof(Element) }
}
}

UPD：我正在使用 OpenGLES 2.0。

我在 4 个月前从你的指南中学到了金额。我试图将它从objective-c转换为swift，直到在图片下绘制相同的矩形。

现在我运行它并转换为 Swift 2.1。它仍然有效并在下面显示相同的图像。

enter image description here

这是我的代码(方法 setupVBO、渲染和结构)

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// Track of all our per-vertex information (currently just color and position)
struct Vertex {
var Position: (CFloat, CFloat, CFloat)
var Color: (CFloat, CFloat, CFloat, CFloat)
}

// Array with all the info for each vertex
var Vertices = [
Vertex(Position: (1, -1, 0) , Color: (1, 0, 0, 1)),
Vertex(Position: (1, 1, 0) , Color: (0, 1, 0, 1)),
Vertex(Position: (-1, 1, 0) , Color: (0, 0, 1, 1)),
Vertex(Position: (-1, -1, 0), Color: (0, 0, 0, 1))
]

// Array that gives a list of triangles to create, by specifying the 3 vertices that make up each triangle
var Indices: [GLubyte] = [
0, 1, 2,
2, 3, 0
]

//helper extensions to pass arguments to GL land
extension Array {
func size () -> Int {
return self.count * sizeofValue(self[0])
}
}

//The best way to send data to OpenGL is through something called Vertex Buffer Objects.
func setupVBOs() { // VBO : Vertex Buffer Objects.

//There are two types of vertex buffer objects – one to keep track of the per-vertex data (like we have in the Vertices array), and one to keep track of the indices that make up triangles (like we have in the Indices array).
glGenBuffers(1, &vertexBuffer)
glBindBuffer(GLenum(GL_ARRAY_BUFFER), vertexBuffer)
glBufferData(GLenum(GL_ARRAY_BUFFER), Vertices.count * sizeofValue(Vertices[0]), Vertices, GLenum(GL_STATIC_DRAW)) // send the data over to OpenGL-land.

glGenBuffers(1, &indexBuffer)
glBindBuffer(GLenum(GL_ELEMENT_ARRAY_BUFFER), indexBuffer)
glBufferData(GLenum(GL_ELEMENT_ARRAY_BUFFER), Indices.count * sizeofValue(Indices[0]), Indices, GLenum(GL_STATIC_DRAW))
}

func render() {
glClearColor(0, 104.0/255.0, 55.0/255.0, 1.0)
glClear(GLbitfield(GL_COLOR_BUFFER_BIT))

//glViewport(0, 0, GLint(frame.size.width), GLint(frame.size.height))
glViewport(0, GLint(frame.size.height/2)/2, GLint(frame.size.width), GLint(frame.size.height/2))

// feed the correct values to the two input variables for the vertex shader – the Position and SourceColor attributes.
glVertexAttribPointer(positionSlot, 3, GLenum(GL_FLOAT), GLboolean(UInt8(GL_FALSE)), GLsizei(sizeof(Vertex)), nil)
glVertexAttribPointer(colorSlot, 4, GLenum(GL_FLOAT), GLboolean(UInt8(GL_FALSE)), GLsizei(sizeof(Vertex)), UnsafePointer<Int>(bitPattern: sizeof(Float) * 3))

// This actually ends up calling your vertex shader for every vertex you pass in, and then the fragment shader on each pixel to display on the screen.
glDrawElements(GLenum(GL_TRIANGLES), GLsizei(Indices.count), GLenum(GL_UNSIGNED_BYTE), nil)

_context.presentRenderbuffer(Int(GL_RENDERBUFFER))
}