Textures and coordinates systems

Unity Engine
,
1

I’m writing an augmented reality app. So far I’ve got the camera data and am rendering it to a GUITexture in a plugin using glTexSubImage2D. But it comes out flipped and rotated because of the different coordinate systems used by the iPhone and OpenGL.

So I’ve looked at:

  1. Rotating the view and flipping/rotating the image using CGContext.
  2. Drawing a textured quad and transforming that.

Number 1 didn’t behave itself. The CGContext stuff didn’t have any effect at all. So I’m doing something wrong there.

I’m stumped on number 2 because of my lack of knowledge of GLES 2.0. I can’t just set verts, texs and render anymore. I just want to do a glDrawArrays().

This is compounded by:

  • I’ll need get a better quality image and only render a portion of the texture when it is rotated.
  • The camera capture using AVFoundation does funny rotation stuff. If I turn the phone 180 the image goes through 360!

Any hints or ideas?

John

2

Solved with something like this, drops frame rate by about 5 frames:

	bitmap = CGBitmapContextCreate(NULL, displayWidth, displayHeight, CGImageGetBitsPerComponent(imageRef), CGImageGetBytesPerRow(imageRef), colorSpaceInfo, bitmapInfo);
	CGContextSaveGState(bitmap);
	
 	float sw = 0.4f; // scale width, fudge factor
	float sh = 1.3333333333f; // scale height, ratio of dest to source
	
	CGContextRotateCTM(bitmap, radians(90));  // rotate
	CGContextScaleCTM(bitmap, sw, -sh);       // flip and scale to size
	CGContextTranslateCTM (bitmap, 300, 0);   // adjust for rotation, scaling and flipping, 300 matching scale fudge
	
	CGRect destRect = CGRectMake(0, 0, displayWidth, displayHeight);
	CGContextDrawImage(bitmap, destRect, imageRef);