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Diffstat (limited to 'examples/opengl3_hello.c')
| -rw-r--r-- | examples/opengl3_hello.c | 199 |
1 files changed, 199 insertions, 0 deletions
diff --git a/examples/opengl3_hello.c b/examples/opengl3_hello.c new file mode 100644 index 0000000..7cc9070 --- /dev/null +++ b/examples/opengl3_hello.c @@ -0,0 +1,199 @@ +/* + Minimal SDL2 + OpenGL3 example. + + Author: https://github.com/koute + + This file is in the public domain; you can do whatever you want with it. + In case the concept of public domain doesn't exist in your jurisdiction + you can also use this code under the terms of Creative Commons CC0 license, + either version 1.0 or (at your option) any later version; for details see: + http://creativecommons.org/publicdomain/zero/1.0/ + + This software is distributed without any warranty whatsoever. + + Compile and run with: gcc opengl3_hello.c `sdl2-config --libs --cflags` -lGL -Wall && ./a.out +*/ + +#define GL_GLEXT_PROTOTYPES + +#include <SDL.h> +#include <SDL_opengl.h> + +#include <stdio.h> + +typedef float t_mat4x4[16]; + +static inline void mat4x4_ortho( t_mat4x4 out, float left, float right, float bottom, float top, float znear, float zfar ) +{ + #define T(a, b) (a * 4 + b) + + out[T(0,0)] = 2.0f / (right - left); + out[T(0,1)] = 0.0f; + out[T(0,2)] = 0.0f; + out[T(0,3)] = 0.0f; + + out[T(1,1)] = 2.0f / (top - bottom); + out[T(1,0)] = 0.0f; + out[T(1,2)] = 0.0f; + out[T(1,3)] = 0.0f; + + out[T(2,2)] = -2.0f / (zfar - znear); + out[T(2,0)] = 0.0f; + out[T(2,1)] = 0.0f; + out[T(2,3)] = 0.0f; + + out[T(3,0)] = -(right + left) / (right - left); + out[T(3,1)] = -(top + bottom) / (top - bottom); + out[T(3,2)] = -(zfar + znear) / (zfar - znear); + out[T(3,3)] = 1.0f; + + #undef T +} + +static const char * vertex_shader = + "#version 130\n" + "in vec2 i_position;\n" + "in vec4 i_color;\n" + "out vec4 v_color;\n" + "uniform mat4 u_projection_matrix;\n" + "void main() {\n" + " v_color = i_color;\n" + " gl_Position = u_projection_matrix * vec4( i_position, 0.0, 1.0 );\n" + "}\n"; + +static const char * fragment_shader = + "#version 130\n" + "in vec4 v_color;\n" + "out vec4 o_color;\n" + "void main() {\n" + " o_color = v_color;\n" + "}\n"; + +typedef enum t_attrib_id +{ + attrib_position, + attrib_color +} t_attrib_id; + +int main( int argc, char * argv[] ) +{ + SDL_Init( SDL_INIT_VIDEO ); + SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 ); + SDL_GL_SetAttribute( SDL_GL_ACCELERATED_VISUAL, 1 ); + SDL_GL_SetAttribute( SDL_GL_RED_SIZE, 8 ); + SDL_GL_SetAttribute( SDL_GL_GREEN_SIZE, 8 ); + SDL_GL_SetAttribute( SDL_GL_BLUE_SIZE, 8 ); + SDL_GL_SetAttribute( SDL_GL_ALPHA_SIZE, 8 ); + + SDL_GL_SetAttribute( SDL_GL_CONTEXT_MAJOR_VERSION, 3 ); + SDL_GL_SetAttribute( SDL_GL_CONTEXT_MINOR_VERSION, 2 ); + SDL_GL_SetAttribute( SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE ); + + static const int width = 800; + static const int height = 600; + + SDL_Window * window = SDL_CreateWindow( "", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, width, height, SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN ); + SDL_GLContext context = SDL_GL_CreateContext( window ); + + GLuint vs, fs, program; + + vs = glCreateShader( GL_VERTEX_SHADER ); + fs = glCreateShader( GL_FRAGMENT_SHADER ); + + int length = strlen( vertex_shader ); + glShaderSource( vs, 1, ( const GLchar ** )&vertex_shader, &length ); + glCompileShader( vs ); + + GLint status; + glGetShaderiv( vs, GL_COMPILE_STATUS, &status ); + if( status == GL_FALSE ) + { + fprintf( stderr, "vertex shader compilation failed\n" ); + return 1; + } + + length = strlen( fragment_shader ); + glShaderSource( fs, 1, ( const GLchar ** )&fragment_shader, &length ); + glCompileShader( fs ); + + glGetShaderiv( fs, GL_COMPILE_STATUS, &status ); + if( status == GL_FALSE ) + { + fprintf( stderr, "fragment shader compilation failed\n" ); + return 1; + } + + program = glCreateProgram(); + glAttachShader( program, vs ); + glAttachShader( program, fs ); + + glBindAttribLocation( program, attrib_position, "i_position" ); + glBindAttribLocation( program, attrib_color, "i_color" ); + glLinkProgram( program ); + + glUseProgram( program ); + + glDisable( GL_DEPTH_TEST ); + glClearColor( 0.5, 0.0, 0.0, 0.0 ); + glViewport( 0, 0, width, height ); + + GLuint vao, vbo; + + glGenVertexArrays( 1, &vao ); + glGenBuffers( 1, &vbo ); + glBindVertexArray( vao ); + glBindBuffer( GL_ARRAY_BUFFER, vbo ); + + glEnableVertexAttribArray( attrib_position ); + glEnableVertexAttribArray( attrib_color ); + + glVertexAttribPointer( attrib_color, 4, GL_FLOAT, GL_FALSE, sizeof( float ) * 6, 0 ); + glVertexAttribPointer( attrib_position, 2, GL_FLOAT, GL_FALSE, sizeof( float ) * 6, ( void * )(4 * sizeof(float)) ); + + const GLfloat g_vertex_buffer_data[] = { + /* R, G, B, A, X, Y */ + 1, 0, 0, 1, 0, 0, + 0, 1, 0, 1, width, 0, + 0, 0, 1, 1, width, height, + + 1, 0, 0, 1, 0, 0, + 0, 0, 1, 1, width, height, + 1, 1, 1, 1, 0, height + }; + + glBufferData( GL_ARRAY_BUFFER, sizeof( g_vertex_buffer_data ), g_vertex_buffer_data, GL_STATIC_DRAW ); + + t_mat4x4 projection_matrix; + mat4x4_ortho( projection_matrix, 0.0f, (float)width, (float)height, 0.0f, 0.0f, 100.0f ); + glUniformMatrix4fv( glGetUniformLocation( program, "u_projection_matrix" ), 1, GL_FALSE, projection_matrix ); + + for( ;; ) + { + glClear( GL_COLOR_BUFFER_BIT ); + + SDL_Event event; + while( SDL_PollEvent( &event ) ) + { + switch( event.type ) + { + case SDL_KEYUP: + if( event.key.keysym.sym == SDLK_ESCAPE ) + return 0; + break; + } + } + + glBindVertexArray( vao ); + glDrawArrays( GL_TRIANGLES, 0, 6 ); + + SDL_GL_SwapWindow( window ); + SDL_Delay( 1 ); + } + + SDL_GL_DeleteContext( context ); + SDL_DestroyWindow( window ); + SDL_Quit(); + + return 0; +} + |