Games202-1 Recap of CG Basics

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a). Graphics Pipeline

GraphicsPipeline

b). OpenGL

OpenGL01a

A. Place objects/models

  • Model specification(模型信息)
  • Model transformation

OpenGL_A

B. Set up an easel(画架)

  • View transformation
  • Create /use a framebuffer

OpenGL_B

C. Attach a canvas to the easel

指定Pass到framebuffer，就和Unity中FS的SV_TARGET一样。

E. you can also paint multiple pictures using the same easel

  • 一个Rendering Pass，使用一个framebuffer，渲染一个或多个texture（shading, depth, etc.）作为输出

  • 即一个framebuffer可以绑定多个纹理（MRT）

  • Multiple Render Target（MRT）是一种指可以使绘制程序在单帧中同时渲染多个Render Target

D. Paint to the canvas

  • This is when vertex / fragment shaders will be used
  • For each vertex in parallel
    • OpenGL calls user-specified vertex shader: Transform vertex (ModelView, Projection), other ops
  • For each primitive, OpenGL rasterizes
    • Generates a fragment for each pixel the fragment covers
  • For each fragment in parallel
    • OpenGL calls user-specified fragment shader: Shading and lighting calculations
    • OpenGL handles z-buffer depth test unless overwritten

Summary: in each pass

  • Specify objects, camera, MVP, etc.

  • Specify framebuffer and input/output textures

  • Specify vertex / fragment shaders

  • (When you have everything specified on the GPU) Render

c). Shading Language(GLSL)

c.1). Initializing

  • Create shader(Vertex and Fragment)

  • Compile shader

  • Attach shader to program

  • Link program

  • Use program

Shader Initialization Code

LinkingShaderProgram

c.2). Phong Shader in Assignment 0

  • Vertex Shader

    VertexShader

    • attribute: 顶点附带的属性，FS中不会出现
    • uniform: 全局变量，由CPU直接传递给GPU
    • varying: 需要插值的变量
    • highp: 高精度
    • gl_Position: 类似于Unity的SV_Position，裁剪空间中的顶点位置；

  • Fragment Shader

    FragmentShader