Talking about 3 common shadow rendering techniques in games (3): shadow map

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Third, shadow map

3.1 Shadow Map Features

• Shadow mapping is a shadow rendering method officially adopted by Unity. The official has done a lot of work in order to integrate the shadow mapping method. As developers, we only need to set the lights in the scene and set the in-game lighting.Whether the gameobject can generate shadows can be completed
• An additional ShadowCaster channel is required
• Easy to implement soft shadows

3.2 Shadow Map Implementation

1. The first step: generate a depth map at the position of the light, and render the depth value in the scene into the depth map, as shown in the following figure, the part of the ground and the place where the block is illuminated by the light need to be rendered, then we willRender their depth values ​​into our depth map.The information of these scenes will be stored in an additional pass called ShadowCaster.

ShadowCaster is a pass specially used to obtain the depth information of the scene. The depth information of this Pass is obtained from the position of the light

2. Step 2:
   • If we want to render the ground plane, and the ground plane is composed of points, if we want to render point P, if we look at it with our naked eyes, then it is easy to see that point P is in shadow,But how does the computer know if point P should be rendered?
   • Compare the rendered depth map with the depth value of point P in the light space, which involves converting the depth value of the camera space of point P into the light space (this involves a lot of low-level knowledge points, you canWatch our open class to learn more).After the point P is transferred to the light space, it can be understood that the point P is 0.9 away from the light and 0.4 away from the camera. Because 0.9>0.4, the point P is in the shadow and does not need to be rendered.
   • More about the underlying knowledge, such as the underlying API, the implementation details of the spatial transformation of point P at the engine level, are also explained in our open courses.

3.3 Soft Shadows

• ShadowMap can also achieve the effect of soft shadow. Soft shadow is an important shadow effect in the game. A shadow is composed of umbra and penumbra. Soft shadow is the so-called penumbra, such as the picture in the lower right corner, around the shadowWith the blurred shadow, how to achieve the effect of soft shadow, you can pay attention to our ShadowMap course, we will tell you the specific implementation method
  

Summary

• Further study content:
  • The solution to the depth jitter problem.
    • A plane on the left of the picture is parked on the runway, because the depth value of the runway map and the shadow of the plane is the same, so there will be jitter.
  • Multi-light real-time shadowing and its performance optimization.
    • If there are multiple light sources in the scene, it will cause multiple shadows to the same object. How to realize real-time shadowing of multiple light sources and its performance optimization, you can continue to pay attention to our course.
• In this article, I mainly explain two aspects of knowledge, the implementation of plane shadows and the use of stencil buffers, and the implementation principles of shadow cones and shadow maps, as well as the realization of shadow effects in some commercial projects.possible problems.
• If you want to learn more about shadow rendering and the learning route in TA, you can scan the QR code to join our open class and receive relevant materials.
  

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For more learning resources, please add QQ: 1517069595 (/enterprise-level performance optimization/hot update/Shader special effects/server/commercial project combat/weekly live broadcast/one-to-one guidance)