shader POSITION

POSITION和SV_POSITION之间的区别在于它们的作用和使用方式。POSITION是在DX10之前使用的输入和输出语义，用于vertex shader的输入和输出以及fragment shader的输入参数。而SV_POSITION是在DX10之后引入的预定义语义，用于vertex shader的输出和fragment shader的输入，它代表着顶点在转换裁剪世界坐标或者像素在视图空间中的位置。如果SV_POSITION作为vertex shader的输出语义，那么最终的顶点位置就被固定了，不能再被后续改变它的空间位置；而如果作为fragment shader的输入语义，它和POSITION是一样的，代表着每个像素点在屏幕上的位置。

相关问题

shader positionVS

引用中提到，SV_POSITION作为vertex shader的输出语义，表示最终的顶点位置，这个位置是固定的，不能再被后续改变它的空间位置。它已经成为了转换裁剪世界的坐标，可以直接用来进入光栅化处理的坐标。而作为fragment shader的输入语义，它代表着每个像素点在屏幕上的位置（实际上是在view space空间中的位置）。中提到，在DX10版本之前，没有引入SV_的预定义语义，所以POSITION被用作vertex shader的输入和输出，以及fragment shader的输入参数。但是在DX10之后，推荐使用SV_POSITION作为vertex shader的输出和fragment shader的输入。但是要注意的是，vertex shader的输入仍然使用POSITION。中提到，shader positionVS是指在vertex shader中计算的位置向量在view space空间中的值。具体来说，在GetVertexPositionInputs方法中，positionOS是物体局部坐标系中的位置向量，通过一系列的坐标变换，得到positionVS，表示这个位置向量在view space空间中的位置。<span class="em">1</span><span class="em">2</span><span class="em">3</span>
#### 引用[.reference_title]
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Cesium Shader

Cesium Shader is a set of shader programs and techniques used to render 3D graphics in the Cesium JavaScript library. These shaders are designed to run on the GPU (graphics processing unit) and provide high-performance rendering of various types of visual effects such as lighting, shadows, reflections, and more.

The Cesium Shader system is built on top of WebGL, a standard API for rendering 3D graphics in web browsers. Cesium Shader uses a combination of vertex shaders and fragment shaders to render 3D models with high fidelity and realism.

The vertex shader is responsible for transforming the 3D model's vertices into screen space coordinates. It also calculates lighting and other effects based on the position and orientation of the camera and other factors.

The fragment shader is responsible for rendering each pixel of the 3D model based on the lighting and other effects calculated by the vertex shader. This includes determining the color and intensity of each pixel, as well as handling transparency and other visual effects.

Cesium Shader also includes advanced techniques such as deferred shading, which allows for complex lighting effects with multiple light sources and shadows. This technique involves rendering the scene in multiple passes, with each pass generating a separate buffer of information that is then combined to produce the final image.

Overall, Cesium Shader provides a powerful and flexible system for rendering 3D graphics in web-based applications. Its use of WebGL and GPU acceleration allows for high-performance rendering of complex scenes and effects, making it a popular choice for a wide range of applications, from games and simulations to scientific data visualization and more.