Real-Time Lens Blur Effects and Focus Control Sungkil Lee, Elmar Eisemann, and Hans-Peter Seidel Sunyeong Kim Nov. 23 nd. 2010

2 Goal ● Real-time Rendering system for defocus blur and lens effects. ● Efficient algorithm for DOF and lens blur effects ● Interactive and intuitive focus control system ● Generalized method for expressive DOF rendering

3 Overview ● Rendering Algorithm ● Optical Aberration ● Controlling Focus and Lens Effects

4 Realistic Lens Blur ● Two steps 1. An Image-based layered representation of the scene using a modified depth-peeling strategy 2. Tracing several rays for each sensor (pixels)

5 Layer Construction ● Layered-image based representation using depth peeling ● Important Observation ● Layer pixels that cannot be reached by any lens rays do not need to be extracted ● A depth-peeled representation is point- sampled at the pixel centers

6 Lens Ray Tracing 1.Intersection test of the aperture and the lens surface 2.Intersection test of the ray against the layer ● Using footprint ● All lens rays in parallel

7 Lens Ray Tracing ● Two challenges ● Bounding footprint for all lens ray in a depth interval ● Computing the min/max values in a footprint region.

8 Bounding the Footprint ● For a depth interval [d 1,d 2 ], It is enough to take the maximum of the COCs at d 1 and d 2. ● Collect intersection point and compute the bounding quad in image space ● Given the bounding quad, Min/Max depth value can be computed

9 Min/Max Depth Value ● Using N-buffer [Décoret 2005] ● Set of textures {T i } of identical resolution ● T 0 is the original image ● Pixel p in T i contains the minimum and maximum value of T 0 inside a square of size 2 i x2 i around p. ● Some pixels are empty. Then, depth is 0.

10 Multi-Layer Packing ● Packing four depth values into a single RGBA texture ● Share one N-Buffer ● Simultaneously testing all four depth values

11 Optical Aberration ● Spherical Aberration ● Curvature of Field (COF) ● Chromatic Aberration ● An empirical equation by Sellmeier

12 Control Focus and Lens Effect ● Controlling Focus for Standard Lens Models ● Thin Lens ● Spherical thick Lens ● Tilt-Shift Photography ● Expressive Focus Control ● Focal Surface ● DOF Interpolation ● Expressive Aberration Effects ● Less accurate simulation with more intuitive control.

13 Result

14 Result

15 Result

16 Result ● Result Video Result Video

17 Discussion ● Extended umbra peeling ● Artifact-free rendering ● In comparison to the single-pass decomposition ● Slower depth peeling ● More cache efficient ● Multiple layers in parallel ● Less and more-predictable arithmetic operations

18 Conclusion ● This is a real-time lens-blur rendering system ● Managing many lens aberration effects ● Simply controlling DOF blur

19 THANK YOU Question or Comment?