此代码绘制了数千个彩色方块的大网格。在每一帧上，它随机选取正方形并将它们设置为新颜色。我想减少CPU负载。设置缓冲区和绘制的理想代码是什么？我对VBO设置和Open GL绘图调用感兴趣。请记住，GPU内存中的顶点颜色总是在变化，但顶点位置永远不会改变。
- (id)initWithBounds:(float)pLeft right:(float)pRight bottom:(float)pBottom top:(float)pTop
{
if (self = [super init]) {
effect = [[GLKBaseEffect alloc] init];
effect.transform.projectionMatrix = GLKMatrix4MakeOrtho(pLeft, pRight, pBottom, pTop, 1, -1);;
self.left = pLeft;
self.right = pRight;
self.bottom = pBottom;
self.top = pTop;
GLfloat gridWidth = self.right - self.left;
GLfloat gridHeight = self.top - self.bottom;
GLfloat halfWidth = gridWidth / 2;
GLfloat halfHeight = gridHeight / 2;
// Create the vertices for each point of the grid
float cellSize = 8.f;
CGSize screenSize = [UIApplication currentSize];
numRows = screenSize.height / cellSize;
numCols = screenSize.width / cellSize;
int verticesPerRow = numCols + 1;
int verticesPerCell = 4;
int numVertices = numRows * numCols * verticesPerCell;
GLKVector2 *vertices = malloc(sizeof(GLKVector2) * numVertices);
int vertexIndex;
// Note use of <= as there is 1 more vertex row/col than numRows/numCols
for (int rowIndex = 0; rowIndex <= numRows; rowIndex++) {
for (int colIndex = 0; colIndex <= numCols; colIndex++) {
vertexIndex = (verticesPerRow * rowIndex) + colIndex;
vertices[vertexIndex] = GLKVector2Make((cellSize * colIndex) - halfWidth, (cellSize * rowIndex) - halfHeight);
}
}
// Create vertexIndices array which colours and vertices arrays wil be based on
int triangleVerticesPerCell = 6; // Define 2 triangles per cell = 2 x 3 vertices
numTriangleVertices = numRows * numCols * triangleVerticesPerCell;
NSLog(@"numTriangleVertices %i", numTriangleVertices);
// numTriangleVertices = 6;
int *vertexIndices = malloc(sizeof(int) * numTriangleVertices);
int i = 0;
for (int rowIndex = 0; rowIndex < numRows; rowIndex++) {
for (int colIndex = 0; colIndex < numCols; colIndex++) {
vertexIndex = (numCols * rowIndex) + colIndex + rowIndex;
vertexIndices[i++] = vertexIndex;
vertexIndices[i++] = vertexIndex + 1;
vertexIndices[i++] = vertexIndex + verticesPerRow + 1;
vertexIndices[i++] = vertexIndex;
vertexIndices[i++] = vertexIndex + verticesPerRow + 1;
vertexIndices[i++] = vertexIndex + verticesPerRow;
}
}
// grid vertices
// int numTriangleVertices = 1 * triangleVerticesPerCell; // 1 cell
triangleVertices = malloc(sizeof(GLKVector2) * numTriangleVertices);
triangleColours = malloc(sizeof(GLKVector4) * numTriangleVertices);
// Sets all values of array to 0
// memset(triangleVertices,0,sizeof(GLKVector2)*numVertices);
GLKVector4 currColour;
for (i = 0; i < numTriangleVertices; i++) {
// Give a new colour to every new set of 6 vertices
if(!(i % 6)) {
currColour = GLKVector4Make(1.0 * arc4random_uniform(101)/100,
1.0 * arc4random_uniform(101)/100,
1.0 * arc4random_uniform(101)/100,
1);
}
triangleColours[i] = currColour;
// Next vertex
triangleVertices[i] = vertices[vertexIndices[i]];
}
// Release memory later
free(vertices);
free(vertexIndices);
[NSTimer scheduledTimerWithTimeInterval:.02
target:self
selector:@selector(timerUpdate:)
userInfo:nil
repeats:YES];
}
return self;
}
-(void) timerUpdate:(NSTimer*)timer {
for(int i = 0; i < 100; i++) {
int randomCellIndex = ((numRows * numCols)-1) * arc4random_uniform(10001)/10000;
// NSLog(@"randomCellIndex %i", randomCellIndex);
// Loop through the random cell's vertices, setting thier colour
GLKVector4 currColour = GLKVector4Make(1.0 * arc4random_uniform(101)/100,
1.0 * arc4random_uniform(101)/100,
1.0 * arc4random_uniform(101)/100,
1);
int startIndex = randomCellIndex * 6;
for (int i = startIndex; i < startIndex + 6; i++) {
triangleColours[i] = currColour;
}
}
}
-(void)render {
// NSLog(@"in EEScene's render");
glClearColor(clearColor.r, clearColor.g, clearColor.b, clearColor.a);
glClear(GL_COLOR_BUFFER_BIT);
[effect prepareToDraw];
glEnableVertexAttribArray(GLKVertexAttribPosition);
glVertexAttribPointer(GLKVertexAttribPosition, 2,
GL_FLOAT, GL_FALSE, 0, triangleVertices);
glEnableVertexAttribArray(GLKVertexAttribColor);
glVertexAttribPointer(GLKVertexAttribColor, 4,
GL_FLOAT, GL_FALSE, 0, triangleColours);
glDrawArrays(GL_TRIANGLES, 0, numTriangleVertices);
glDisableVertexAttribArray(GLKVertexAttribPosition);
glDisableVertexAttribArray(GLKVertexAttribColor);
}