삼각형 그리기

glClear

• State-setting function
  • State가 OpenGL context에 저장됨
  • glClearAccum(), glClearColor(),  glClearDepth(),  glClearIndex(),  glClearStencil()

 

• State-using function
  • OpenGL context에 저장된 State를 이용 glClear()
  • OR 연산자 가능

GL_COLOR_BUFFER_BIT	현재 색 쓰기에 사용할 수 있는 버퍼입니다.
GL_DEPTH_BUFFER_BIT	깊이 버퍼입니다.
GL_ACCUM_BUFFER_BIT	누적 버퍼입니다.
GL_STENCIL_BUFFER_BIT	스텐실 버퍼입니다.

 

---

VAO(Vertex Array Object)

• void glGenVertexArrays(GLsizei n, GLuint *arrays)
• void glBindVertexArray(GLuint array)
• void glEnableVertexAttribArray(GLuint index)
• void glVertexAttribPointer(GLuint index, GLint size, GLenum type, GLboolean normalized, GLsizei stride, const void * pointer)
  • size : 변수 갯수(ex. 3 => vec3)
  • type : 변수 타입(ex. float)
  • pointer : offset

---

VBO(Vertex Buffer Object)

• void glGenBuffers(GLsizei n, GLuint* buffers)
• void glBindBuffer(GLenum target, GLuint buffer)
  • target : GL_ARRAY_BUFFER, GL_ELEMENT_ARRAY_BUFFER, etc.. 
• void glBufferData(GLenum target, GLsizeiptr size, const void* data, GLenum usage)
  • usage : "STATIC | DYNAMIC | STREAM" && "DRAW | COPY | READ" 조합
    • ex) GL_STATIC_DRAW
  • GL_STATIC_DRAW: 딱 한번만 세팅되고 앞으로 계속 쓸 예정
  • GL_DYNAMIC_DRAW: 앞으로 데이터가 자주 바뀔 예정
  • GL_STREAM_DRAW: 딱 한번만 세팅되고 몇번 쓰다 버려질 예정

---

순서

• VAO binding
• VBO binding
• vertex attribute setting

---

Shader

• GLuint glCreateShader(GLenum shaderType)
  • shaderType : GL_VERTEX_SHADER, GL_FRAGMENT_SHADER, etc ..
• void glShaderSource(GLuint shader, GLsizei count, const GLchar **string, const GLint *length)
• void glCompileShader(GLuint shader)
  • void glGetShaderiv(GLuint shader, GLenum pname, GLint *params)
    • pname : GL_COMPILE_STATUS
  • void glGetShaderInfoLog( GLuint shader, GLsizei maxLength, GLsizei *length, GLchar *infoLog)

---

Program

• void glAttachShader( GLuint program, GLuint shader)
• void glLinkProgram( GLuint program)
  • void glGetProgramiv(GLuint program, GLenum pname, GLint *params)
    
    • pname : GL_LINK_STATUS
  • void glGetProgramInfoLog( GLuint program, GLsizei maxLength, GLsizei *length, GLchar *infoLog)