如何使用glew
使用glew
glew也是一个扩展库，包含了OpenGL中许多核心及扩展函数，现在的版本是1.7，支持OpenGL4.2，可以到这里下载：http://glew.sourceforge.net/
下载了glew库的话，那么可以直接使用该扩展，但是使用之前首先要确定你的显卡是否支持该扩展。方法如下：
首先还是要判断显卡是否支持该扩展
如何判断显卡所支持的扩展:
使用函数glGetString，看一下它的原型：
const GLubyte * glGetString( GLenum name )
我们以GL_EXTENSIONS为参数调用该函数，就能获得当前显卡所支持的所有扩展，像下面这样:
const GLubyte *str = glGetString(GL_EXTENSIONS) ; cout << str << endl ;
1．包含头文件glew.h，注意这里和上面不同，这回glut.h要放在glew.h的后面了
像下面这样
#include <GL/glew.h> #include <GL/glut.h>
然后就可以在程序中直接使用glBlendEquation了，其他扩展的判断和使用方法与此类似。
最后还有一点切记！那就是还要调用glewInit() ;来初始化一下方可使用扩展，如下：
GLenum err = glewInit();
if (GLEW_OK != err)
{
MessageBoxA(NULL, "error", "My Window", 1);
}
.在project->setting中,打开link选项卡,加上glew.lib
或在文件中加上#progmma comment(lib, "glew.lib")
好了，现在可以放心使用扩展了，赶快继续你的OpenGL之旅吧！
为了查看显卡到底支持哪些扩展，折腾了好久。
#include <iostream>
#include <GL/glew.h>
using namespace std;
int main()
{
GLenum err = glewInit();
if (err != GLEW_OK )
{
fprintf(stderr, "Error: %s\n", glewGetErrorString(err));
exit (-2);
}
int NumberOfExtensions;
glGetIntegerv(GL_NUM_EXTENSIONS, &NumberOfExtensions);
for(int i=0; i<NumberOfExtensions; i++)
{
const GLubyte *ccc=glGetStringi(GL_EXTENSIONS, i);
//Now, do something with ccc
cout << ccc << endl;
}
system("pause");
}这是最初的代码，前面所说的glGetString函数在OpenGL3.0之后废除了，为了使用最新的OpenGL4.2，在官网查到了最新使用方法。
在link->input中写入glew32.lib，编译报link错误，不认识glGetIntegerv函数，但是在glew.h能发现这个函数。google了好久没发现好的解决方案。不过后来在glew官网<说明链接>查到了问题所在，使用glew必须有一个opengl context。最简单的方案是用glut创建一个context。增加了2句话后得到结果。
#include <iostream>
#include <GL/glew.h>
#include <gl/glut.h>
using namespace std;
int main()
{
glutCreateWindow("GLEW Test");//get an openGL context
GLenum err = glewInit();
if (err != GLEW_OK )
{
fprintf(stderr, "Error: %s\n", glewGetErrorString(err));
exit (-2);
}
int NumberOfExtensions;
glGetIntegerv(GL_NUM_EXTENSIONS, &NumberOfExtensions);
for(int i=0; i<NumberOfExtensions; i++)
{
const GLubyte *ccc=glGetStringi(GL_EXTENSIONS, i);
//Now, do something with ccc
cout << ccc << endl;
}
system("pause");
}结果：（其实我还是不知道显卡到底支不支持最新的OpenGL 4.2）
GL_ARB_blend_func_extended GL_ARB_color_buffer_float GL_ARB_compatibility GL_ARB_copy_buffer GL_ARB_depth_buffer_float GL_ARB_depth_clamp GL_ARB_depth_texture GL_ARB_draw_buffers GL_ARB_draw_elements_base_vertex GL_ARB_draw_instanced GL_ARB_ES2_compatibility GL_ARB_explicit_attrib_location GL_ARB_fragment_coord_conventions GL_ARB_fragment_program GL_ARB_fragment_program_shadow GL_ARB_fragment_shader GL_ARB_framebuffer_object GL_ARB_framebuffer_sRGB GL_ARB_geometry_shader4 GL_ARB_get_program_binary GL_ARB_half_float_pixel GL_ARB_half_float_vertex GL_ARB_imaging GL_ARB_instanced_arrays GL_ARB_map_buffer_range GL_ARB_multisample GL_ARB_multitexture GL_ARB_occlusion_query GL_ARB_occlusion_query2 GL_ARB_pixel_buffer_object GL_ARB_point_parameters GL_ARB_point_sprite GL_ARB_provoking_vertex GL_ARB_robustness GL_ARB_sampler_objects GL_ARB_seamless_cube_map GL_ARB_separate_shader_objects GL_ARB_shader_bit_encoding GL_ARB_shader_objects GL_ARB_shading_language_100 GL_ARB_shading_language_include GL_ARB_shadow GL_ARB_sync GL_ARB_texture_border_clamp GL_ARB_texture_buffer_object GL_ARB_texture_compression GL_ARB_texture_compression_rgtc GL_ARB_texture_cube_map GL_ARB_texture_env_add GL_ARB_texture_env_combine GL_ARB_texture_env_crossbar GL_ARB_texture_env_dot3 GL_ARB_texture_float GL_ARB_texture_mirrored_repeat GL_ARB_texture_multisample GL_ARB_texture_non_power_of_two GL_ARB_texture_rectangle GL_ARB_texture_rg GL_ARB_texture_rgb10_a2ui GL_ARB_texture_swizzle GL_ARB_timer_query GL_ARB_transpose_matrix GL_ARB_uniform_buffer_object GL_ARB_vertex_array_bgra GL_ARB_vertex_array_object GL_ARB_vertex_buffer_object GL_ARB_vertex_program GL_ARB_vertex_shader GL_ARB_vertex_type_2_10_10_10_rev GL_ARB_viewport_array GL_ARB_window_pos GL_ATI_draw_buffers GL_ATI_texture_float GL_ATI_texture_mirror_once GL_S3_s3tc GL_EXT_texture_env_add GL_EXT_abgr GL_EXT_bgra GL_EXT_bindable_uniform GL_EXT_blend_color GL_EXT_blend_equation_separate GL_EXT_blend_func_separate GL_EXT_blend_minmax GL_EXT_blend_subtract GL_EXT_compiled_vertex_array GL_EXT_Cg_shader GL_EXT_depth_bounds_test GL_EXT_direct_state_access GL_EXT_draw_buffers2 GL_EXT_draw_instanced GL_EXT_draw_range_elements GL_EXT_fog_coord GL_EXT_framebuffer_blit GL_EXT_framebuffer_multisample GL_EXTX_framebuffer_mixed_formats GL_EXT_framebuffer_object GL_EXT_framebuffer_sRGB GL_EXT_geometry_shader4 GL_EXT_gpu_program_parameters GL_EXT_gpu_shader4 GL_EXT_multi_draw_arrays GL_EXT_packed_depth_stencil GL_EXT_packed_float GL_EXT_packed_pixels GL_EXT_pixel_buffer_object GL_EXT_point_parameters GL_EXT_provoking_vertex GL_EXT_rescale_normal GL_EXT_secondary_color GL_EXT_separate_shader_objects GL_EXT_separate_specular_color GL_EXT_shadow_funcs GL_EXT_stencil_two_side GL_EXT_stencil_wrap GL_EXT_texture3D GL_EXT_texture_array GL_EXT_texture_buffer_object GL_EXT_texture_compression_dxt1 GL_EXT_texture_compression_latc GL_EXT_texture_compression_rgtc GL_EXT_texture_compression_s3tc GL_EXT_texture_cube_map GL_EXT_texture_edge_clamp GL_EXT_texture_env_combine GL_EXT_texture_env_dot3 GL_EXT_texture_filter_anisotropic GL_EXT_texture_format_BGRA8888 GL_EXT_texture_integer GL_EXT_texture_lod GL_EXT_texture_lod_bias GL_EXT_texture_mirror_clamp GL_EXT_texture_object GL_EXT_texture_shared_exponent GL_EXT_texture_sRGB GL_EXT_texture_swizzle GL_EXT_texture_type_2_10_10_10_REV GL_EXT_timer_query GL_EXT_vertex_array GL_EXT_vertex_array_bgra GL_IBM_rasterpos_clip GL_IBM_texture_mirrored_repeat GL_KTX_buffer_region GL_NV_alpha_test GL_NV_blend_minmax GL_NV_blend_square GL_NV_complex_primitives GL_NV_conditional_render GL_NV_copy_depth_to_color GL_NV_copy_image GL_NV_depth_buffer_float GL_NV_depth_clamp GL_NV_explicit_multisample GL_NV_fbo_color_attachments GL_NV_fence GL_NV_float_buffer GL_NV_fog_distance GL_NV_fragdepth GL_NV_fragment_program GL_NV_fragment_program_option GL_NV_fragment_program2 GL_NV_framebuffer_multisample_coverage GL_NV_geometry_shader4 GL_NV_gpu_program4 GL_NV_half_float GL_NV_light_max_exponent GL_NV_multisample_coverage GL_NV_multisample_filter_hint GL_NV_occlusion_query GL_NV_packed_depth_stencil GL_NV_parameter_buffer_object GL_NV_parameter_buffer_object2 GL_NV_path_rendering GL_NV_pixel_data_range GL_NV_point_sprite GL_NV_primitive_restart GL_NV_register_combiners GL_NV_register_combiners2 GL_NV_shader_buffer_load GL_NV_texgen_reflection GL_NV_texture_barrier GL_NV_texture_compression_vtc GL_NV_texture_env_combine4 GL_NV_texture_expand_normal GL_NV_texture_lod_clamp GL_NV_texture_multisample GL_NV_texture_rectangle GL_NV_texture_shader GL_NV_texture_shader2 GL_NV_texture_shader3 GL_NV_transform_feedback GL_NV_vertex_array_range GL_NV_vertex_array_range2 GL_NV_vertex_buffer_unified_memory GL_NV_vertex_program GL_NV_vertex_program1_1 GL_NV_vertex_program2 GL_NV_vertex_program2_option GL_NV_vertex_program3 GL_NVX_conditional_render GL_NVX_gpu_memory_info GL_OES_depth24 GL_OES_depth32 GL_OES_depth_texture GL_OES_element_index_uint GL_OES_fbo_render_mipmap GL_OES_get_program_binary GL_OES_mapbuffer GL_OES_packed_depth_stencil GL_OES_rgb8_rgba8 GL_OES_standard_derivatives GL_OES_texture_3D GL_OES_texture_float GL_OES_texture_float_linear GL_OES_texture_half_float GL_OES_texture_half_float_linear GL_OES_texture_npot GL_OES_vertex_array_object GL_OES_vertex_half_float GL_SGIS_generate_mipmap GL_SGIS_texture_lod GL_SGIX_depth_texture GL_SGIX_shadow GL_SUN_slice_accum GL_WIN_swap_hint WGL_EXT_swap_control