Function #

Buffer #

• glClearBuffer

void glClearBufferfv (GLenum buffer, GLint drawBuffer, const GLfloat *value);

clear buffer of drawBuffer with value

Shader & Program object manage #

• glCreateShader

GLuint glCreateShader (GLenum type);

create type of shader(structure that manage shader code compile and linking it) and return GLuint as identifier.

• glShaderSource

void glShaderSource (GLuint shader, GLsizei count, const GLchar* const *string, const GLint *length);

will add more explains

• glCompileShader

void glCompileShader (GLuint shader);

Compile shader indenfied shader.

• glCreateProgram

GLuint glCreateProgram (void);

create a program object and return its identifier.

• glAttachShader

void glAttachShader (GLuint program, GLuint shader);

attach shader to program

• glLinkProgram

void glLinkProgram (GLuint program);

as its name

• glDeleteShader

void glDeleteShader (GLuint shader);

as its name

• glDeleteProgram

void glDeleteProgram (GLuint program);

as its name

Vertex Shader manage #

Vertex Array #

• glGenVertexArrays

void glGenVertexArrays (GLsizei n, GLuint *arrays);

Generate n number of VAO(Vertex Array Object)s in arrays.
since this function access GLuint as array, it requires arrays’ address as parameter.

• glBindVertexArray

void glBindVertexArray (GLuint array);

bind array(VAO) to current context.

ood #

• glDrawArrays

void glDrawArrays (GLenum mode, GLint first, GLsizei count);

send vertices to pipeline. started from first, count of vertices with premitive mode
mode example: GL_POINTS, GL_LINES, GL_TRIANGLES, GL_TRIANGLE_STRIP, GL_TRIANGLE_FAN, GL_PATCHES, …

• glVertexAttrib

void glVertexAttrib4fv(GLuint index, const GLfloat *v);

set 4fv of vertex attribute to layout(loaction = index).
4fv means 4 float vector(array)

Tessellation Shader manage #

• glPatchParameteri

void glPatchParameteri (GLenum pname, GLint value);

tname example: GL_PATCH_VETICES

Geometry Shader manage #

Shader Built-in variable #

• gl_Position

(out) represents transform of vertex

• gl_VertexID

specify id used in vertex shader
(in) Ex: glDrawArrays) started from first , count number of vertex

• gl_InvocationID

(in) used fo 0-based index of gl_in, gl_out

• gl_TessLevelInner
• gl_TessLevelOuter

(out) Tessellation factor variable array
contain tessellation level

• gl_TessCoord

(in)barycentric coodinate of vertex

EmitVertex()

make vertex with gl_Position of geometry shader

EndPrimitive()

automatically called when geometry shader end

• gl_FragCoord

(in)coordinate of fragment to manipulate

General #

• gl_in
• gl_out

not simple variable, but array

• floor

float floor (float f);

floor function in glsl.
i.e. return integer part of f.
trunc funtion is used in absolute value’s case.

• fract

float fract (float f);

return fractional part of f.

• mix

vec4 mix (vec4 A, vec4 B, float t);

linear interpolation.
has sevelar verstions take different dimensional vectors or scalars as A and B,
t shows iterpolating parameter represented by scalar or matching vector.

layout #

• Vertex
  layout (location = 0) in vec4 variablename;
  //location used as attribute index

• Tesselation Control
  layout (vertices = 3) out;
  //output control point(vertices) per patch

• Tesselation Evaluation
  layout (triangles, equal_spacing, cw) in;
  //setting for tessellation mode

• Geometry
  layout (triangles) in;
  layout (points, max_vertices = 3) out;
  //get input as triangle and divide them into points

• Fragment

• Compute
  layout (local_size_x = 32, local_size_y = 32) in;
  //local workgroup szie is 32*32

extension #

#extension GL_extension_feature_en : enable  //enable feature both device support it or not    
#extension GL_extension_feature_re : required  //if this extensio is not replaceable, use required for assertive code    
    
#if GL_extension_feature_en    
//extension's name will be defined with macro so you can manage code    
#else    
//alternative codes if extension doesn't supported    
#endif

Fixed Block #

Pixel Operations #

scissor test => stencil test => depth test => 

Coordinate space #

• Model space (=object space)
  local origin following coordinate space

• World space
  global origin following coordinate space

• View space (=camera, =eye space)
  relative coordinate space to viewer

• Clip space
  coordniate space after projection on homogeneous coordinate

• Normalized device coordinate(NDC) space
  coordinate space after dividing clip space by w component

• Window space
  window origin following coordinate space

Transform #

• View - Clip Transform
  can be performed by projection matrix : orthographic, perspective, etc…
  occurs after Model - View Transform.

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