What differences should you be aware of between raytracing
and rasterization in hybrid rendering for real-time lighting.

In this article we will show you how to use rays to create different effects (for example in 3D configurator projects) and to compare the results with your rasterized counterpart.

In the following video you will find a demo for hybrid rendering:

Better rendering through hybrid raytracing.

Shading a pixel is essentially about finding its context: where it is in the world, where the light comes from, whether the light comes, whether the light is blocked by other surfaces or bounces off them. Rasterers are not particularly good at determining this, since each triangle is treated independently of the rest. There are obvious ways to circumvent this problem to some extent, but these can be unnecessary, confused, or of limited effieciency and often result in mediocre image quality. Raytracers, on the other hand, are extremely good at finding out what the environment looks like, but tend to be much slower due to the higher complexity of the calculations. A hybrid renderer can combine the speed of the raster and the context awareness of the raytracers by rasterizing a G buffer representing all visible surfaces before using its raytracing capabilities to calculate lighting and reflections for those surfaces.

Shadows.

Dealing with shadows in a grid is anything but intuitive and requires some logistics: the scene must be rendered from the perspective of each individual light, stored in a texture and projected onto itself during the lighting phase. Worse still, it is far from being even close to acceptable in terms of quality: These shadows are very susceptible to aliasing (because a pixel seen by the light does not match a pixel seen by the camera) or acne (because a shadow image texel stores a single depth value but can cover a large area). In addition, most rasters need to support special shadow map types such as cubic shadows or cascaded shadow maps, which greatly increases the complexity of the renderer.

In a raytracer, a single code path can handle all shading scenarios. More importantly, the shadowing process is as simple and intuitive as firing a ray from the surface to the light source and checking if anything was hit along the way. The PowerVR ray tracing architecture exposes so-called fast feeler rays, which only check the presence of geometry along the ray, making them particularly suitable for efficient shadow rendering.