选择在OpenGL ES 2.0(iOS)中绘制的对象的最佳方法是什么？
我在画点。
最佳答案
这是选色的工作原型(prototype)，已在大多数旧的iPad上进行了测试，并且运行良好。实际上，这是项目InCube Chess的一部分，您可以在应用商店中找到它。您将看到的主要代码位于从GLKViewController派生的类中，如下所示:
@interface IncubeViewController : GLKViewController
这意味着您具有glkview:((GLKView *)self.view)。
这也是一些属性:
@property (strong, nonatomic) EAGLContext *context;
@property (strong, nonatomic) GLKBaseEffect *effect;
不要忘记将它们合成到您的* .m文件中。
@synthesize context = _context;
@synthesize effect = _effect;
想法是您 table 上有棋子(或3d场景中的一些对象)，并且需要通过点击屏幕在棋子列表中找到棋子。也就是说，您需要将2D屏幕点击坐标(在这种情况下为@point)转换为棋子实例。
每件作品都有其唯一的ID，我称之为“印章”。您可以将密封件从1分配到某物。选择功能返回通过丝锥坐标找到的密封件。然后获得印章，您可以通过以下方式轻松地在哈希表或数组中找到您的作品:
-(Piece *)findPieceBySeal:(GLuint)seal
{
/* !!! Black background in off screen buffer produces 0 seals. This allows
to quickly filter out taps that did not select anything (will be
mentioned below) !!! */
if (seal == 0)
return nil;
PieceSeal *sealKey = [[PieceSeal alloc] init:s];
Piece *p = [sealhash objectForKey:sealKey];
[sealKey release];
return p;
}
“sealhash”是NSMutableDictionary。
现在，这是主要的选择功能。请注意，我的glkview是抗锯齿的，您不能使用其缓冲区进行颜色选择。这意味着您需要创建自己的屏幕外缓冲区，并且禁用抗锯齿功能仅出于拾取目的。
- (NSUInteger)findSealByPoint:(CGPoint)point
{
NSInteger height = ((GLKView *)self.view).drawableHeight;
NSInteger width = ((GLKView *)self.view).drawableWidth;
Byte pixelColor[4] = {0,};
GLuint colorRenderbuffer;
GLuint framebuffer;
glGenFramebuffers(1, &framebuffer);
glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
glGenRenderbuffers(1, &colorRenderbuffer);
glBindRenderbuffer(GL_RENDERBUFFER, colorRenderbuffer);
glRenderbufferStorage(GL_RENDERBUFFER, GL_RGBA8_OES, width, height);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0_OES, GL_RENDERBUFFER, colorRenderbuffer);
GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
if (status != GL_FRAMEBUFFER_COMPLETE) {
NSLog(@"Framebuffer status: %x", (int)status);
return 0;
}
[self render:DM_SELECT];
CGFloat scale = UIScreen.mainScreen.scale;
glReadPixels(point.x * scale, (height - (point.y * scale)), 1, 1, GL_RGBA, GL_UNSIGNED_BYTE, pixelColor);
glDeleteRenderbuffers(1, &colorRenderbuffer);
glDeleteFramebuffers(1, &framebuffer);
return pixelColor[0];
}
请注意，此功能考虑了显示比例(视网膜或新iPad)。
这是上面函数中使用的render()函数。请注意，出于渲染目的，它使用某种背景色清除了缓冲区，并且为了选择大小写，将其设置为黑色，以便您可以轻松检查是否轻按了任何一块。
- (void) render:(DrawMode)mode
{
if (mode == DM_RENDER)
glClearColor(backgroundColor.r, backgroundColor.g,
backgroundColor.b, 1.0f);
else
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
/* Draw all pieces. */
for (int i = 0; i < [model->pieces count]; i++) {
Piece *p = [model->pieces objectAtIndex:i];
[self drawPiece:p mode:mode];
}
}
接下来是我们如何绘制作品。
- (void) drawPiece:(Piece *)p mode:(DrawMode)mode
{
PieceType type;
[self pushMatrix];
GLKMatrix4 modelViewMatrix = self.effect.transform.modelviewMatrix;
GLKMatrix4 translateMatrix = GLKMatrix4MakeTranslation(p->drawPos.X,
p->drawPos.Y,
p->drawPos.Z);
modelViewMatrix = GLKMatrix4Multiply(modelViewMatrix, translateMatrix);
GLKMatrix4 rotateMatrix;
GLKMatrix4 scaleMatrix;
if (mode == DM_RENDER) {
scaleMatrix = GLKMatrix4MakeScale(p->scale.X,
p->scale.Y, p->scale.Z);
} else {
/* !!! Make the piece a bit bigger in off screen buffer for selection
purposes so that we always sure that we tapped it correctly by
finger.*/
scaleMatrix = GLKMatrix4MakeScale(p->scale.X + 0.2,
p->scale.Y + 0.2, p->scale.Z + 0.2);
}
modelViewMatrix = GLKMatrix4Multiply(modelViewMatrix, scaleMatrix);
self.effect.transform.modelviewMatrix = modelViewMatrix;
type = p->type;
if (mode == DM_RENDER) {
/* !!! Use real pieces color and light on for normal drawing !!! */
GLKVector4 color[pcLast] = {
[pcWhite] = whitesColor,
[pcBlack] = blacksColor
};
self.effect.constantColor = color[p->color];
self.effect.light0.enabled = GL_TRUE;
} else {
/* !!! Use piece seal for color. Important to turn light off !!! */
self.effect.light0.enabled = GL_FALSE;
self.effect.constantColor = GLKVector4Make(p->seal / 255.0f,
0.0f, 0.0f, 0.0f);
}
/* Actually normal render the piece using it geometry buffers. */
[self renderPiece:type];
[self popMatrix];
}
这是使用上面显示的功能的方法。
- (IBAction) tapGesture:(id)sender
{
if ([(UITapGestureRecognizer *)sender state] == UIGestureRecognizerStateEnded) {
CGPoint tap = [(UITapGestureRecognizer *)sender locationInView:self.view];
Piece *p = [self findPieceBySeal:[self findSealByPoint:tap]];
/* !!! Do something with your selected object !!! */
}
}
基本上就是这个。您将拥有非常精确的挑选算法，该算法比光线追踪或其他方法要好得多。
这里是推送/流行矩阵事物的助手。
- (void)pushMatrix
{
assert(matrixSP < sizeof(matrixStack) / sizeof(GLKMatrix4));
matrixStack[matrixSP++] = self.effect.transform.modelviewMatrix;
}
- (void)popMatrix
{
assert(matrixSP > 0);
self.effect.transform.modelviewMatrix = matrixStack[--matrixSP];
}
这里也使用了我使用的glkview设置/清理功能。
- (void)viewDidLoad
{
[super viewDidLoad];
self.context = [[[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2] autorelease];
if (!self.context)
NSLog(@"Failed to create ES context");
GLKView *view = (GLKView *)self.view;
view.context = self.context;
view.drawableDepthFormat = GLKViewDrawableDepthFormat24;
[self setupGL];
}
- (void)viewDidUnload
{
[super viewDidUnload];
[self tearDownGL];
if ([EAGLContext currentContext] == self.context)
[EAGLContext setCurrentContext:nil];
self.context = nil;
}
- (void)setupGL
{
[EAGLContext setCurrentContext:self.context];
self.effect = [[[GLKBaseEffect alloc] init] autorelease];
if (self.effect) {
self.effect.useConstantColor = GL_TRUE;
self.effect.colorMaterialEnabled = GL_TRUE;
self.effect.light0.enabled = GL_TRUE;
self.effect.light0.diffuseColor = GLKVector4Make(1.0f, 1.0f, 1.0f, 1.0f);
}
/* !!! Draw antialiased geometry !!! */
((GLKView *)self.view).drawableMultisample = GLKViewDrawableMultisample4X;
self.pauseOnWillResignActive = YES;
self.resumeOnDidBecomeActive = YES;
self.preferredFramesPerSecond = 30;
glDisable(GL_DITHER);
glEnable(GL_CULL_FACE);
glEnable(GL_DEPTH_TEST);
glLineWidth(2.0f);
/* Load pieces geometry */
[self loadGeometry];
}
- (void)tearDownGL
{
drawReady = NO;
[EAGLContext setCurrentContext:self.context];
[self unloadGeometry];
}
希望这会有所帮助，并可能永远解决“领料问题” :)
关于ios - iOS上的OpenGL ES 2.0对象选取，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/6774197/