OpenGL Introduction

A introduction to OpenGL for beginners

Transcript

1. OpenGL Introduction Bruce Tsai
2. State machine! Primitives! Buffers! Shaders! Attributes and uniforms! Drawing
4. Port Crane Crates inside each container are our instances! Containers are OpenGL ’s objects ! textures, shaders, meshes! Port crane is OpenGL API 4 State Machine
5. Primitives GL_POINTS! GL_LINES! GL_LINE_STRIP! GL_LINE_LOOP! GL_TRIANGLES! GL_TRIANGLE_STRIP! GL_TRIANGLE_FAN 5
8. Rendering Settings void glPolygonMode(GLenum face, GLenum mode);! ! void glFrontFace(GLenum mode);! ! void glCullFace(GLenum mode); GL_FRONT_AND_BACK GL_POINT GL_LINE GL_FILL GL_CW GL_CCW GL_FRONT GL_BACK GL_FRONT_AND_BACK 8
9. Buffers Temporary optimized storage! Render buffers! Frame buffers! Buffer objects 9
10. Render Buffer Color! Store final colored (RGB) image! Depth! Store final Z depth information! Stencil! Store visible part of object 10
11. Frame Buffer Store final image! Combination of render buffers 11
12. Buffer Object Hold informations about 3D objects! Structures! Indices 12
13. Structures vs. Indices {v1, v2, v3}, {v1, v3, v4}, …! ! {v1, v2, v3, v4, …}
 (0, 1, 2, 0, 2, 3, …) 13
14. One Buffer at a Time OpenGL GL_ARRAY_BUFFER GL_ELEMENT_ARRAY_BUFFER GL_TEXTURE_BUFFER Buffer1 Buffer2 Buffer3 Buffer4
15. Create Buffer void glGenBuffers(GLsizei n, GLuint *buffers);! ! void glBindBuffers(GLenum target, GLuint buffer); GL_ARRAY_BUFFER GL_ELEMENT_ARRAY_BUFFER 15
16. Set Buffer Data void glBufferData(GLenum target, GLsizeiptr size, const GLvoid *data, GLenum usage);! ! ! void glBufferSubData(GLenum target, GLintptr offset, GLsizeiptr size, const GLvoid *data); _STATIC_ _DYNAMIC_ _STREAM_ _DRAW _READ _COPY GL_STATIC_DRAW 16
17. Copy Buffer Data void glCopyBufferSubData(GLenum readtarget, GLenum writetarget, GLintptr readoffset, GLintptr writeoffset, GLsizeiptr size); 17
18. Get Buffer Data void glGetBufferSubData(GLenum target, GLintptr offset, GLsizeiptr size, GLvoid *data); 18
19. Access Content Buffer void* glMapBuffer(GLenum target, GLenum access);! ! GLboolean glUnmapBuffer(GLenum target) GL_READ_ONLY GL_WRITE_ONLY GL_READ_WRITE 19
21. Create Shader GLuint glCreateShader(GLenum type);! ! void glShaderSource(GLuint shader, GLsizei count, const GLchar **string, const GLint *length);! void glCompileShader(GLuint shader); 21 GL_VERTEX_SHADER GL_FRAGMENT_SHADER
22. Create Program GLuint glCreateProgram(void);! void glAttachShader(GLuint program, GLuint shader);! void glLinkProgram(GLuint program);! void glUseProgram(GLuint program); 22
23. Attributes and Uniforms
24. Attribute Location 1. Defined fixed location in shader! 2. Bind attribute location before linking shader code! void glBindAttribLocation(GLuint program, GLuint index, const GLchar *name);! 3. Get attribute location after linking shader code! GLint glGetAttribLocation(GLuint program, const GLchar *name); 24
25. Uniform Location Get uniform location after linking shader code! GLint glGetUniformLocation(GLuint program, const GLchar *name); 25
26. Define Attribute Values void glVertexAttrib{1234}f(GLuint index, GLfloat value[N]);! void glVertexAttrib{1234}fv(GLuint index, const GLfloat *values); 26
27. Attribute Pointer void glVertexAttribPointer(GLuint index, GLint size, GLenum type, GLboolean normalized, GLsizei stride, const GLvoid *ptr);! ! void glGenVertexArrays(GLsizei n, GLuint *arrays);! void glBindVertexArrays(GLuint array); 27 Required while using glVertexAttribPointer
28. Using Attribute Pointer void glEnableVertexAttribArray(GLuint index);! void glDisableVertexAttribArray(GLuint index); 28
29. Define Uniform Values void glUniform{1234}{if}(GLint index, T value[N]);! void glUniform{1234}{if}v(GLint index, GLsizei count, const T *value);! void glUniformMatrix{234}fv(GLint index, GLsizei count, GLboolean transpose, const GLfloat *value); 29
30. Clear void glClearColor(GLflozt red, GLfloat green, GLfloat blue, GLfloat alpha);! void glClear(GLbitfield mask); 30 GL_COLOR_BUFFER_BIT GL_DEPTH_BUFFER_BIT GL_STENCIL_BUFFER_BIT
31. Drawing void glDrawArrays(GLenum mode, GLint first, GLsizei count);! ! ! void glDrawElements(GLenum mode, GLsizei count, GLenum type, const GLvoid *indices); 31 GL_POINTS GL_LINES GL_LINE_STRIP GL_LINE_LOOP GL_TRIANGLES GL_TRIANGLE_STRIP GL_TRIANGLE_FAN GL_UNSIGNED_BYTE GL_UNSIGNED_SHORT GL_UNSIGNED_INT
32. Restarting Index void glPrimitiveRestartIndex(GLuint index); 32
33. Sample v0! p(-1,-1,0,1)! c(1,1,1,1) v1! p(1,-1,0,1)! c(1,1,0,1) v2! p(-1,1,0,1)! c(1,0,1,1) v3! p(1,1,0,1)! c(0,1,1,1)
34. References http://blog.db-in.com/all-about-opengl-es-2-x-part-1/! http://www.dreamstime.com/stock-images-port-cranes- image25107404! http://blog.db-in.com/all-about-opengl-es-2-x-part-2/! OpenGL Programming Guide