I write this note to record general ideas and notable details to let me pick them up easily in the following procedure.
I decide to sort them after I find it is easy to forget the chapters you reads before.
1 Image synthesis
Introduce pinhole camera model and determination the average light (color) in one pixel.
2 Tracing rays
2.1 Forward rat tracing
follow photons from their origin at the light and into the scene, tracing their path in a forward direction, just as the photons themselves would have traveled it. unworkable: too much calculation, low computation efficiency
2.2 Backward ray tracing
Follow a ray backwards to find out where it may have begun.
note: ”first object hit by a ray” = ”the first object might have emitted that ray”
Term ”ray tracing” is often referred to backward ray tracing.
2.3 Ray combination
pixel ray/eye ray
illumination ray/shadow ray
2.4 ~ 2.7
These sections introduce the above concepts in detail.
1.Illumination ray or shadow ray are those coming from light source directly.
2. Don’t be confused of the literal meaning of incident ray. We are using backward ray tracing, so incident ray refers to rays into our eye or reflected from the surface.
3 Recursive visibility
Use recursive algorithm in ray tracing
3.1 Surface physics
Introduction of an eye ray propagated through a scene and a ray tree.
4 Aliasing common in signal processing
4.1 Spatial aliasing
cause jaggies with low sampling rate and resolution.
4.2 Temporal aliasing
1.Things are happening too fast to record accurately.
2. Small objects move across the screen and they will blink on or off, or pop.
3. Smoothly moving edges are another kind of pop.
list some popular approaches to solve aliasing
4.4 ~ 4.7
adaptive super sampling
stochastic ray tracing
statistical ray tracing
The above approaches seem to relative with many algorithms in other fields. Maybe I can use some popular methods in signal processing, control theory and machine learning to get better performance in image.
The rendering equation can express how light bounces around in a scene mathematically. It is useful and one powerful way to solve it is ray tracing.