전체코드

#include <sb7.h>

// Undefine this to take color from screen space
#define INTERPOLATE_COLOR

class colorfromposition_app : public sb7::application
{
    void init()
    {
        static const char title[] = "OpenGL SuperBible - Simple Triangle";

        sb7::application::init();

        memcpy(info.title, title, sizeof(title));
    }

    virtual void startup()
    {
#ifndef INTERPOLATE_COLOR
        static const char * vs_source[] =
        {
            "#version 420 core                                                          \n"
            "                                                                           \n"
            "void main(void)                                                            \n"
            "{                                                                          \n"
            "    const vec4 vertices[] = vec4[](vec4( 0.25, -0.25, 0.5, 1.0),           \n"
            "                                   vec4(-0.25, -0.25, 0.5, 1.0),           \n"
            "                                   vec4( 0.25,  0.25, 0.5, 1.0));          \n"
            "                                                                           \n"
            "    gl_Position = vertices[gl_VertexID];                                   \n"
            "}                                                                          \n"
        };

        static const char * fs_source[] =
        {
            "#version 420 core                                                          \n"
            "                                                                           \n"
            "out vec4 color;                                                            \n"
            "                                                                           \n"
            "void main(void)                                                            \n"
            "{                                                                          \n"
            "    color = vec4(sin(gl_FragCoord.x * 0.25) * 0.5 + 0.5,                   \n"
            "                 cos(gl_FragCoord.y * 0.25) * 0.5 + 0.5,                   \n"
            "                 sin(gl_FragCoord.x * 0.15) * cos(gl_FragCoord.y * 0.1),  \n"
            "                 1.0);                                                     \n"
            "}                                                                          \n"
        };
#else
        static const char * vs_source[] =
        {
            "#version 420 core                                                          \n"
            "                                                                           \n"
            "out vec4 vs_color; \n"
            "void main(void)                                                            \n"
            "{                                                                          \n"
            "    const vec4 vertices[] = vec4[](vec4( 0.25, -0.25, 0.5, 1.0),           \n"
            "                                   vec4(-0.25, -0.25, 0.5, 1.0),           \n"
            "                                   vec4( 0.25,  0.25, 0.5, 1.0));          \n"
            "    const vec4 colors[] = vec4[](vec4(1.0, 0.0, 0.0, 1.0),                 \n"
            "                                 vec4(0.0, 1.0, 0.0, 1.0),                 \n"
            "                                 vec4(0.0, 0.0, 1.0, 1.0));                \n"
            "                                                                           \n"
            "    gl_Position = vertices[gl_VertexID];                                   \n"
            "    vs_color = colors[gl_VertexID];                                        \n"
            "}                                                                          \n"
        };

        static const char * fs_source[] =
        {
            "#version 420 core                                                          \n"
            "                                                                           \n"
            "in vec4 vs_color;                                                          \n"
            "out vec4 color;                                                            \n"
            "                                                                           \n"
            "void main(void)                                                            \n"
            "{                                                                          \n"
            "    color = vs_color;                                                      \n"
            "}                                                                          \n"
        };
#endif

        program = glCreateProgram();
        GLuint fs = glCreateShader(GL_FRAGMENT_SHADER);
        glShaderSource(fs, 1, fs_source, NULL);
        glCompileShader(fs);

        GLuint vs = glCreateShader(GL_VERTEX_SHADER);
        glShaderSource(vs, 1, vs_source, NULL);
        glCompileShader(vs);

        glAttachShader(program, vs);
        glAttachShader(program, fs);

        glLinkProgram(program);

        glGenVertexArrays(1, &vao);
        glBindVertexArray(vao);
    }

    virtual void render(double currentTime)
    {
        static const GLfloat green[] = { 0.0f, 0.25f, 0.0f, 1.0f };
        glClearBufferfv(GL_COLOR, 0, green);

        glUseProgram(program);
        glDrawArrays(GL_TRIANGLES, 0, 3);
    }

    virtual void shutdown()
    {
        glDeleteVertexArrays(1, &vao);
        glDeleteProgram(program);
    }

private:
    GLuint          program;
    GLuint          vao;
};

DECLARE_MAIN(colorfromposition_app)

설명

        static const char * vs_source[] =
        {
            "#version 420 core                                                          \n"
            "                                                                           \n"
            "out vec4 vs_color; \n"
            "void main(void)                                                            \n"
            "{                                                                          \n"
            "    const vec4 vertices[] = vec4[](vec4( 0.25, -0.25, 0.5, 1.0),           \n"
            "                                   vec4(-0.25, -0.25, 0.5, 1.0),           \n"
            "                                   vec4( 0.25,  0.25, 0.5, 1.0));          \n"
            "    const vec4 colors[] = vec4[](vec4(1.0, 0.0, 0.0, 1.0),                 \n"
            "                                 vec4(0.0, 1.0, 0.0, 1.0),                 \n"
            "                                 vec4(0.0, 0.0, 1.0, 1.0));                \n"
            "                                                                           \n"
            "    gl_Position = vertices[gl_VertexID];                                   \n"
            "    vs_color = colors[gl_VertexID];                                        \n"
            "}                                                                          \n"
        };

vs_source 안의

vs_color를 out으로 선언한후

        static const char * fs_source[] =
        {
            "#version 420 core                                                          \n"
            "                                                                           \n"
            "in vec4 vs_color;                                                          \n"
            "out vec4 color;                                                            \n"
            "                                                                           \n"
            "void main(void)                                                            \n"
            "{                                                                          \n"
            "    color = vs_color;                                                      \n"
            "}                                                                          \n"
        };

fs_source 안에서 vs_color를 in으로 받아서 color를 결정 한다.