diff --git a/examples/CMakeLists.txt b/examples/CMakeLists.txt index 138a7816..fe946f5c 100644 --- a/examples/CMakeLists.txt +++ b/examples/CMakeLists.txt @@ -11,6 +11,10 @@ if (MSVC) add_definitions(-D_CRT_SECURE_NO_WARNINGS) endif() +if (GLFW_USE_OSMESA) + add_definitions(-DUSE_NATIVE_OSMESA) +endif() + include_directories("${GLFW_SOURCE_DIR}/deps") if (WIN32) @@ -31,6 +35,7 @@ set(TINYCTHREAD "${GLFW_SOURCE_DIR}/deps/tinycthread.h" add_executable(boing WIN32 MACOSX_BUNDLE boing.c ${ICON} ${GLAD}) add_executable(gears WIN32 MACOSX_BUNDLE gears.c ${ICON} ${GLAD}) add_executable(heightmap WIN32 MACOSX_BUNDLE heightmap.c ${ICON} ${GLAD}) +add_executable(offscreen offscreen.c ${ICON} ${GLAD}) add_executable(particles WIN32 MACOSX_BUNDLE particles.c ${ICON} ${TINYCTHREAD} ${GETOPT} ${GLAD}) add_executable(simple WIN32 MACOSX_BUNDLE simple.c ${ICON} ${GLAD}) add_executable(splitview WIN32 MACOSX_BUNDLE splitview.c ${ICON} ${GLAD}) diff --git a/examples/offscreen.c b/examples/offscreen.c new file mode 100644 index 00000000..68ac8dbf --- /dev/null +++ b/examples/offscreen.c @@ -0,0 +1,171 @@ +//======================================================================== +// Offscreen rendering example +// Copyright (c) Camilla Berglund +// +// This software is provided 'as-is', without any express or implied +// warranty. In no event will the authors be held liable for any damages +// arising from the use of this software. +// +// Permission is granted to anyone to use this software for any purpose, +// including commercial applications, and to alter it and redistribute it +// freely, subject to the following restrictions: +// +// 1. The origin of this software must not be misrepresented; you must not +// claim that you wrote the original software. If you use this software +// in a product, an acknowledgment in the product documentation would +// be appreciated but is not required. +// +// 2. Altered source versions must be plainly marked as such, and must not +// be misrepresented as being the original software. +// +// 3. This notice may not be removed or altered from any source +// distribution. +// +//======================================================================== + +#include +#include + +#if USE_NATIVE_OSMESA + #define GLFW_EXPOSE_NATIVE_OSMESA + #include +#endif + +#include "linmath.h" + +#include +#include + +#define STB_IMAGE_WRITE_IMPLEMENTATION +#include + +static const struct +{ + float x, y; + float r, g, b; +} vertices[3] = +{ + { -0.6f, -0.4f, 1.f, 0.f, 0.f }, + { 0.6f, -0.4f, 0.f, 1.f, 0.f }, + { 0.f, 0.6f, 0.f, 0.f, 1.f } +}; + +static const char* vertex_shader_text = +"uniform mat4 MVP;\n" +"attribute vec3 vCol;\n" +"attribute vec2 vPos;\n" +"varying vec3 color;\n" +"void main()\n" +"{\n" +" gl_Position = MVP * vec4(vPos, 0.0, 1.0);\n" +" color = vCol;\n" +"}\n"; + +static const char* fragment_shader_text = +"varying vec3 color;\n" +"void main()\n" +"{\n" +" gl_FragColor = vec4(color, 1.0);\n" +"}\n"; + +static void error_callback(int error, const char* description) +{ + fprintf(stderr, "Error: %s\n", description); +} + +int main(void) +{ + GLFWwindow* window; + GLuint vertex_buffer, vertex_shader, fragment_shader, program; + GLint mvp_location, vpos_location, vcol_location; + float ratio; + int width, height; + mat4x4 mvp; + char* buffer; + + glfwSetErrorCallback(error_callback); + + if (!glfwInit()) + exit(EXIT_FAILURE); + + glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 2); + glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0); + glfwWindowHint(GLFW_VISIBLE, GLFW_FALSE); + + window = glfwCreateWindow(640, 480, "Simple example", NULL, NULL); + if (!window) + { + glfwTerminate(); + exit(EXIT_FAILURE); + } + + glfwMakeContextCurrent(window); + gladLoadGLLoader((GLADloadproc) glfwGetProcAddress); + + // NOTE: OpenGL error checks have been omitted for brevity + + glGenBuffers(1, &vertex_buffer); + glBindBuffer(GL_ARRAY_BUFFER, vertex_buffer); + glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW); + + vertex_shader = glCreateShader(GL_VERTEX_SHADER); + glShaderSource(vertex_shader, 1, &vertex_shader_text, NULL); + glCompileShader(vertex_shader); + + fragment_shader = glCreateShader(GL_FRAGMENT_SHADER); + glShaderSource(fragment_shader, 1, &fragment_shader_text, NULL); + glCompileShader(fragment_shader); + + program = glCreateProgram(); + glAttachShader(program, vertex_shader); + glAttachShader(program, fragment_shader); + glLinkProgram(program); + + mvp_location = glGetUniformLocation(program, "MVP"); + vpos_location = glGetAttribLocation(program, "vPos"); + vcol_location = glGetAttribLocation(program, "vCol"); + + glEnableVertexAttribArray(vpos_location); + glVertexAttribPointer(vpos_location, 2, GL_FLOAT, GL_FALSE, + sizeof(vertices[0]), (void*) 0); + glEnableVertexAttribArray(vcol_location); + glVertexAttribPointer(vcol_location, 3, GL_FLOAT, GL_FALSE, + sizeof(vertices[0]), (void*) (sizeof(float) * 2)); + + glfwGetFramebufferSize(window, &width, &height); + ratio = width / (float) height; + + glViewport(0, 0, width, height); + glClear(GL_COLOR_BUFFER_BIT); + + mat4x4_ortho(mvp, -ratio, ratio, -1.f, 1.f, 1.f, -1.f); + + glUseProgram(program); + glUniformMatrix4fv(mvp_location, 1, GL_FALSE, (const GLfloat*) mvp); + glDrawArrays(GL_TRIANGLES, 0, 3); + +#if USE_NATIVE_OSMESA + glfwGetOSMesaColorBuffer(window, &width, &height, NULL, (void**) &buffer); +#else + buffer = calloc(4, width * height); + glReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, buffer); +#endif + + // Write image Y-flipped because OpenGL + stbi_write_png("offscreen.png", + width, height, 4, + buffer + (width * 4 * (height - 1)), + -width * 4); + +#if USE_NATIVE_OSMESA + // Here is where there's nothing +#else + free(buffer); +#endif + + glfwDestroyWindow(window); + + glfwTerminate(); + exit(EXIT_SUCCESS); +} +