I had been achieve 3D Object picking use color coding, if anybody want the demo, please call me and tell me your e-mail.
opengl es 2.0 object picking on ios using color coding
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24-06-2023 - |
Вопрос
I have read a lot of tutorials about using color coding to achieve 3D Object picking on iOS. But I'm not sure how to do it. Anyone who can get me a demo written by Objective-C .
The related issues just like this:
OpenGL ES 2.0 Object Picking on iOS (Using Color Coding)
many thanks. luo
Решение 2
Другие советы
I have achieved picking object in OpenGL ES scene using snapshot. Here is the key code:
-(GLKVector4)pickAtX:(GLuint)x Y:(GLuint)y {
GLKView *glkView = (GLKView*)[self view];
UIImage *snapshot = [glkView snapshot];
GLKVector4 objColor = [snapshot pickPixelAtX:x Y:y];
return objColor;
}
And, then in your tapGesture method, you just need to add this:
const CGPoint loc = [recognizer locationInView:[self view]];
GLKVector4 objColor = [self pickAtX:loc.x Y:loc.y];
if (GLKVector4AllEqualToVector4(objColor, GLKVector4Make(1.0f, 0.0f, 0.0f, 1.0f)))
{
//do something.......
}
of course, you should add this :
@implementation UIImage (NDBExtensions)
- (GLKVector4)pickPixelAtX:(NSUInteger)x Y:(NSUInteger)y {
CGImageRef cgImage = [self CGImage];
size_t width = CGImageGetWidth(cgImage);
size_t height = CGImageGetHeight(cgImage);
if ((x > width) || (y > height))
{
GLKVector4 baseColor = GLKVector4Make(0.0f, 0.0f, 0.0f, 1.0f);
return baseColor;
}
CGDataProviderRef provider = CGImageGetDataProvider(cgImage);
CFDataRef bitmapData = CGDataProviderCopyData(provider);
const UInt8* data = CFDataGetBytePtr(bitmapData);
size_t offset = ((width * y) + x) * 4;
//UInt8 b = data[offset+0];
float b = data[offset+0];
float g = data[offset+1];
float r = data[offset+2];
float a = data[offset+3];
CFRelease(bitmapData);
NSLog(@"R:%f G:%f B:%f A:%f", r, g, b, a);
GLKVector4 objColor = GLKVector4Make(r/255.0f, g/255.0f, b/255.0f, a/255.0f);
return objColor;
}
it is useful to achieve object picking in OpenGL ES scene.
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