渲染顶点缓冲区阵列OenGL ES2

Question

我想渲染一个VBO数组，但结果不正确。当我第一次使用GLPaint（OpenGLES v2）设置绘制它们时，我将它们保存到一个数组中。如果你想帮助我，这里是我有的示例项目。 https://drive.google.com/file/d/0B0pG5vRVzBTzUTZPYWNoenhkcWs/edit?usp=sharing

////// Store VBOs when drawing this is done in renderLineFromPoint (from GLPaint) 
- (void) renderLineFromPoint:(CGPoint)start toPoint:(CGPoint)end 
{ 

static GLfloat*  vertexBuffer = NULL; 
static NSUInteger vertexMax = 64; 
NSUInteger   vertexCount = 0, 
count, 
i; 

[EAGLContext setCurrentContext:context]; 
glBindFramebuffer(GL_FRAMEBUFFER, viewFramebuffer); 

// Convert locations from Points to Pixels 
CGFloat scale = self.contentScaleFactor; 
start.x *= scale; 
start.y *= scale; 
end.x *= scale; 
end.y *= scale; 

// Allocate vertex array buffer 
if(vertexBuffer == NULL) 
    vertexBuffer = malloc(vertexMax * 2 * sizeof(GLfloat)); 

// Add points to the buffer so there are drawing points every X pixels 
count = MAX(ceilf(sqrtf((end.x - start.x) * (end.x - start.x) + (end.y - start.y) * (end.y - start.y))/kBrushPixelStep), 1); 

for(i = 0; i < count; ++i) 
{ 
    if(vertexCount == vertexMax) 
    { 
     vertexMax = 2 * vertexMax; 
     vertexBuffer = realloc(vertexBuffer, vertexMax * 2 * sizeof(GLfloat)); 
    } 

    vertexBuffer[2 * vertexCount + 0] = start.x + (end.x - start.x) * ((GLfloat)i/(GLfloat)count); 
    vertexBuffer[2 * vertexCount + 1] = start.y + (end.y - start.y) * ((GLfloat)i/(GLfloat)count); 
    vertexCount += 1; 
} 

glBindBuffer(GL_ARRAY_BUFFER, vboId); 
glBufferData(GL_ARRAY_BUFFER, vertexCount*2*sizeof(GLfloat), vertexBuffer, GL_DYNAMIC_DRAW); 

glEnableVertexAttribArray(ATTRIB_VERTEX); 
glVertexAttribPointer(ATTRIB_VERTEX, 2, GL_FLOAT, GL_FALSE, 0, 0); 

// Render the vertex array 
glVertexPointer(2, GL_FLOAT, 0, vertexBuffer); 
glDrawArrays(GL_POINTS, 0, vertexCount); 

// Display the buffer 
glBindRenderbuffer(GL_RENDERBUFFER, viewRenderbuffer); 
[context presentRenderbuffer:GL_RENDERBUFFER]; 

// Store VBO for undo 
VBOHolder *vboHolder = [[VBOHolder alloc]init]; 
vboHolder.vertexCount = vertexCount; 
vboHolder.vbo = vertexBuffer; 
[vboHolderArray addObject:vboHolder]; 

} 

////// Here is the problem: I clear the screen and then try to re-render the VBOs 
-(void)renderSavedVertexBufferes 
{ 

    for (VBOHolderModel *vboh in vboHolderArray) 
    { 
    if (vboh.vertexCount == 0) 
    { 
     continue; 
    } 

    NSUInteger vertexCount = vboh.vertexCount; 

    glBindBuffer(GL_ARRAY_BUFFER, vboId); 
    glBufferData(GL_ARRAY_BUFFER, vertexCount*2*sizeof(GLfloat), vboh.vbo, GL_DYNAMIC_DRAW); 

    glEnableVertexAttribArray(ATTRIB_VERTEX); 
    glVertexAttribPointer(ATTRIB_VERTEX, 2, GL_FLOAT, GL_FALSE, 0, 0); 

    // Render the vertex array 
    glVertexPointer(2, GL_FLOAT, 0, vboh.vbo); 
    glDrawArrays(GL_POINTS, 0, vertexCount); 

    // Display the buffer 
    glBindRenderbuffer(GL_RENDERBUFFER, viewRenderbuffer); 
    [context presentRenderbuffer:GL_RENDERBUFFER]; 

    } 
} 


////// VBOHolderModel looks like this, it wraps the vbo so it can be put in NSMutableArray 
@interface VBOHolderModel : NSObject 
{ 
    GLfloat *vbo; 
    NSUInteger vertexCount; 

} 

它基本上是一个撤消...当按下撤消它应该只删除3，因为这是最后一搏，但删除了一切，并绘制第二图像中显示的点。

Answer 1

我找到了这个问题的答案在下面的行

// Allocate vertex array buffer
if(vertexBuffer == NULL)
vertexBuffer = malloc(vertexMax * 2 * sizeof(GLfloat));

的问题是，存储顶点数组都是一样的！当vertexBuffer为null时，它仅在init上分配一次内存。其他一些代码有所改变，如果你想更新，请告诉我。