Study notes: unity customsrp-10-point and spot shadows

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This section is mainly based on the previous section Add live shadows .

Similarly, this section contains a lot of content , It's also a bit complicated , If you look at the directional light shadow in front , It should be easy to understand .

summary ：
1. Blend baking and real-time shadows for point and spot lights
2. Add a second shadow set
3. Use perspective projection to render and sample shadows （ Spotlights ）
4. Use custom cube maps （ Point source ）

The overall idea of real-time shadow ：
1. Apply for shadow space , Cache the shadow map of the current frame .
2. Render shadow to shadow map .
3. Sample shadow maps , Mix colors .

notes ： In the second step , For different types of light , There are different details .
1. For directional light , Using orthogonal projection rendering , The shadow map is rendered in different regions according to the number of cascades . Find the correct area when sampling .
2. For spotlights , Render with perspective projection
3. For point lights , Perspective projection rendering 6 Time , Find the correct area when sampling

Each kind of light can be cascaded , But it will lead to more complexity , And more performance consuming , For example, a point light source plus 4 Cascades , Rendering required 4x6=24 Time .

One last point ： There are many shadow problems in the whole process of rendering sampling , The authors have given general answers , Think for yourself .