#include <sb7.h>

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

        sb7::application::init();

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

    virtual void startup()
    {
        static const char * vs_source[] =
        {
            "#version 410 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 * tcs_source[] =
        {
            "#version 410 core                                                                 \n"
            "                                                                                  \n"
            "layout (vertices = 3) out;                                                        \n"
            "                                                                                  \n"
            "void main(void)                                                                   \n"
            "{                                                                                 \n"
            "    if (gl_InvocationID == 0)                                                     \n"
            "    {                                                                             \n"
            "        gl_TessLevelInner[0] = 5.0;                                               \n"
            "        gl_TessLevelOuter[0] = 5.0;                                               \n"
            "        gl_TessLevelOuter[1] = 5.0;                                               \n"
            "        gl_TessLevelOuter[2] = 5.0;                                               \n"
            "    }                                                                             \n"
            "    gl_out[gl_InvocationID].gl_Position = gl_in[gl_InvocationID].gl_Position;     \n"
            "}                                                                                 \n"
        };

        static const char * tes_source[] =
        {
            "#version 410 core                                                                 \n"
            "                                                                                  \n"
            "layout (triangles, equal_spacing, cw) in;                                         \n"
            "                                                                                  \n"
            "void main(void)                                                                   \n"
            "{                                                                                 \n"
            "    gl_Position = (gl_TessCoord.x * gl_in[0].gl_Position) +                       \n"
            "                  (gl_TessCoord.y * gl_in[1].gl_Position) +                       \n"
            "                  (gl_TessCoord.z * gl_in[2].gl_Position);                        \n"
            "}                                                                                 \n"
        };

        static const char * fs_source[] =
        {
            "#version 410 core                                                 \n"
            "                                                                  \n"
            "out vec4 color;                                                   \n"
            "                                                                  \n"
            "void main(void)                                                   \n"
            "{                                                                 \n"
            "    color = vec4(0.0, 0.8, 1.0, 1.0);                             \n"
            "}                                                                 \n"
        };

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

        GLuint tcs = glCreateShader(GL_TESS_CONTROL_SHADER);
        glShaderSource(tcs, 1, tcs_source, NULL);
        glCompileShader(tcs);

        GLuint tes = glCreateShader(GL_TESS_EVALUATION_SHADER);
        glShaderSource(tes, 1, tes_source, NULL);
        glCompileShader(tes);

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

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

        glLinkProgram(program);

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

        glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
    }

    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_PATCHES, 0, 3);
    }

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

private:
    GLuint          program;
    GLuint          vao;
};

DECLARE_MAIN(tessellatedtri_app)

전체코드

#include <sb7.h>
#include <math.h>

class singlepoint_app : public sb7::application
{
    void init()
    {
        static const char title[] = "OpenGL SuperBible - Single Point";

        sb7::application::init();

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

    virtual void startup()
    {
        static const char * vs_source[] =
        {
            "#version 410 core                                                 \n"
            "                                                                  \n"
            "layout (location = 0) in vec4 offset;                             \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"
            "    // Add 'offset' to our hard-coded vertex position             \n"
            "    gl_Position = vertices[gl_VertexID] + offset;                 \n"
            "}                                                                 \n"
        };

        static const char * fs_source[] =
        {
            "#version 410 core                                                 \n"
            "                                                                  \n"
            "out vec4 color;                                                   \n"
            "                                                                  \n"
            "void main(void)                                                   \n"
            "{                                                                 \n"
            "    color = vec4(0.0, 0.8, 1.0, 1.0);                             \n"
            "}                                                                 \n"
        };
		
        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);

        GLfloat attrib[] = { (float)sin(currentTime) * 0.5f,
                             (float)cos(currentTime) * 0.6f,
                             0.0f, 0.0f };

        glVertexAttrib4fv(0, attrib); // 1번째 파라미터 쉐이더의 layout (location = 0) 와 대칭

        glDrawArrays(GL_TRIANGLES, 0, 3);
    }

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

private:
    GLuint          program;
    GLuint          vao;
};

DECLARE_MAIN(singlepoint_app)

설명

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

        glUseProgram(program);

        GLfloat attrib[] = { (float)sin(currentTime) * 0.5f,
                             (float)cos(currentTime) * 0.6f,
                             0.0f, 0.0f };

        glVertexAttrib4fv(0, attrib); // 1번째 파라미터 쉐이더의 layout (location = 0) 와 대칭

        glDrawArrays(GL_TRIANGLES, 0, 3);
    }

render 함수내

        GLfloat attrib[] = { (float)sin(currentTime) * 0.5f,
                             (float)cos(currentTime) * 0.6f,
                             0.0f, 0.0f };

        glVertexAttrib4fv(0, attrib); // 1번째 파라미터 쉐이더의 layout (location = 0) 와 대칭 

부분을 보면 0값은 

static const char * vs_source[] =
        {
            "#version 410 core                                                 \n"
            "                                                                  \n"
            "layout (location = 0) in vec4 offset;                             \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"
            "    // Add 'offset' to our hard-coded vertex position             \n"
            "    gl_Position = vertices[gl_VertexID] + offset;                 \n"
            "}                                                                 \n"
        };

layout (location = 0) in vec4 offset; 의 offset 변수 인덱스번호를 의미 한다.

전체코드

#include <sb7.h>

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

        sb7::application::init();

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

    virtual void startup()
    {
        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(0.0, 0.8, 1.0, 1.0);                             \n"
            "}                                                                 \n"
        };

        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(singlepoint_app)

설명

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"
        };

vs_source[] 코드 내의 gl_VertexID는

render 함수안 glDrawArrays(GL_TRIANGLES, 0, 3); 호출시

인자값 3에 따라 0,1,2가 gl_VertexID로 입력됨

2.2 쉐이더 사용하기

[예제 2-5]

#include <sb7.h>

class singlepoint_app : public sb7::application
{
    void init()
    {
        static const char title[] = "OpenGL SuperBible - Single Point";

        sb7::application::init();

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

    virtual void startup()
    {
        static const char * vs_source[] =
        {
            "#version 420 core                             \n"
            "                                              \n"
            "void main(void)                               \n"
            "{                                             \n"
            "    gl_Position = vec4(0.0, 0.0, 0.5, 1.0);   \n"
            "}                                             \n"
        };

        static const char * fs_source[] =
        {
            "#version 420 core                             \n"
            "                                              \n"
            "out vec4 color;                               \n"
            "                                              \n"
            "void main(void)                               \n"
            "{                                             \n"
            "    color = vec4(0.0, 0.8, 1.0, 1.0);         \n"
            "}                                             \n"
        };



		/* 쉐이더 */
		// Vertex Shader 위치 정보
		// Fragment Shader 색상
		// Geometry Shader 정점 변환

        program = glCreateProgram(); // 쉐이더 프로그램 생성


        GLuint fs = glCreateShader(GL_FRAGMENT_SHADER); // 1번 쉐이더 생성
        glShaderSource(fs, 1, fs_source, NULL);
        glCompileShader(fs);

        GLuint vs = glCreateShader(GL_VERTEX_SHADER); // 2번 쉐이더 생성
        glShaderSource(vs, 1, vs_source, NULL);
        glCompileShader(vs);



        glAttachShader(program, vs); // 프로그램에 사용될 쉐이더 등록
		glAttachShader(program, fs); // 프로그램에 사용될 쉐이더 등록

        glLinkProgram(program);

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

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

        glUseProgram(program);

        glPointSize(40.0f);

        glDrawArrays(GL_POINTS, 0, 1);
    }

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

private:
    GLuint          program;
    GLuint          vao;
};

DECLARE_MAIN(singlepoint_app)

쉐이더 종류

 - Vertex Shader 위치 정보
 - Fragment Shader 색상
 - Geometry Shader 정점 변환