c++ - 尝试实现渲染到纹理

Question

我在使用 OpenGL 3 实现纹理渲染时遇到问题。

我的问题是，在渲染到帧缓冲区之后，渲染的对象看起来变形了，这可能意味着某处发生了错误的转换。这没有意义，因为当不使用我的帧缓冲区时对象渲染良好(见帖子底部)。

目前的结果是这样的:

Current result http://k.minus.com/jZVgUuLYRtapv.jpg

预期的结果是这样的(或类似的东西，这刚刚被 GIMP 处理过): Expected http://k.minus.com/jA5rLM8lmXQYL.jpg

因此这意味着我在我的帧缓冲区设置代码或其他地方做错了什么。但是我看不到什么。

---

FBO是通过以下函数设置的:

unsigned int fbo_id;
unsigned int depth_buffer;
int m_FBOWidth, m_FBOHeight;
unsigned int m_TextureID;

void initFBO() {
    m_FBOWidth = screen_width;
    m_FBOHeight = screen_height;

    glGenRenderbuffers(1, &depth_buffer);
    glBindRenderbuffer(GL_RENDERBUFFER, depth_buffer);
    glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, m_FBOWidth, m_FBOHeight);

    glGenTextures(1, &m_TextureID);
    glBindTexture(GL_TEXTURE_2D, m_TextureID);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, m_FBOWidth, m_FBOHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0);
    glBindTexture(GL_TEXTURE_2D, 0);

    glGenFramebuffers(1, &fbo_id);
    glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fbo_id);

    glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depth_buffer);
    glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, m_TextureID, 0);

    assert(glCheckFramebufferStatus(GL_FRAMEBUFFER) == GL_FRAMEBUFFER_COMPLETE);
    glBindFramebuffer(GL_FRAMEBUFFER, 0);
}

这是我的绘图框代码，它只需要一个变换矩阵并调用适当的函数。 P的当前值是一个投影矩阵，是 View 矩阵(V)的单位矩阵。

void drawBox(const Matrix4& M) {
    const Matrix4 MVP = M * V * P;

    if (boundshader) {
        glUniformMatrix4fv((*boundshader)("MVP"), 1, GL_FALSE, &MVP[0]);
    }

    glBindVertexArray(vaoID);
    glDrawElements(GL_TRIANGLES, sizeof(cube.polygon)/sizeof(cube.polygon[0]), GL_UNSIGNED_INT, 0);
}

void drawStaticBox() {
    Matrix4 M(1);
    translate(M, Vector3(0,0,-50));

    drawBox(M);
}

void drawRotatingBox() {
    Matrix4 M(1);
    rotate(M, rotation(Vector3(1, 0, 0), rotation_x));
    rotate(M, rotation(Vector3(0, 1, 0), rotation_y));
    rotate(M, rotation(Vector3(0, 0, 1), rotation_z));
    translate(M, Vector3(0,0,-50));

    drawBox(M);
}

以及GLUT调用的显示函数。

void OnRender() {
    /////////////////////////////////////////
    // Render to FBO

    glClearColor(0, 0, 0.2f,0);

    glBindFramebuffer(GL_FRAMEBUFFER, fbo_id);
    glViewport(0, 0, m_FBOWidth, m_FBOHeight);
    glClear(GL_COLOR_BUFFER_BIT| GL_DEPTH_BUFFER_BIT);
    GL_CHECK_ERRORS

    colorshader.Use();
    boundshader = &colorshader;

    drawRotatingBox();

    colorshader.UnUse();

    /////////////////////////////////////////
    // Render to Window

    glClearColor(0, 0, 0, 0);

    glBindFramebuffer(GL_FRAMEBUFFER, 0);
    glViewport(0, 0, screen_width, screen_height);
    glClear(GL_COLOR_BUFFER_BIT| GL_DEPTH_BUFFER_BIT);
    GL_CHECK_ERRORS

    texshader.Use();
    boundshader = &texshader;

    glBindTexture(GL_TEXTURE_2D, m_TextureID);
    drawStaticBox();

    texshader.UnUse();

    // Swap le buffers
    glutSwapBuffers();
}

---

还有...强制性纹理着色器代码

顶点

#version 330

in vec2 vUV;
in vec3 vVertex;
smooth out vec2 vTexCoord;

uniform mat4 MVP;
void main()
{
   vTexCoord = vUV;
   gl_Position = MVP*vec4(vVertex,1);
}

片段

#version 330
smooth in vec2 vTexCoord;
out vec4 vFragColor;

uniform sampler2D textureMap;

void main(void)
{
   vFragColor = texture(textureMap, vTexCoord);
}

---

以下是不使用 FBO 逻辑时呈现的内容: What is rendered to the FBO http://k.minus.com/jiP7kTOSLLvHk.jpg

---

...帮助？

关于我可能做错了什么的任何想法？可应要求提供更多来源。

Answer 1

无需仔细查看您的代码，这是一些肯定有效的示例 FBO 代码(将茶壶设置为纹理动画，将纹理绘制到旋转立方体的侧面)。

#include <GL/glew.h>
#include <GL/glut.h>

#include <cmath>
#include <iostream>

using namespace std;

namespace render
{
    int width, height;
    float aspect;

    void init();
    void reshape(int width, int height);
    void display();

    int const fbo_width = 512;
    int const fbo_height = 512;

    GLuint fb, color, depth;
};

void idle();

int main(int argc, char *argv[])
{
    glutInit(&argc, argv);
    glutInitDisplayMode( GLUT_RGBA | GLUT_DOUBLE | GLUT_DEPTH );

    glutCreateWindow("FBO test");
    glutDisplayFunc(render::display);
    glutReshapeFunc(render::reshape);
    glutIdleFunc(idle);

    glewInit();

    render::init();
    glutMainLoop();

    return 0;
}

void idle()
{
    glutPostRedisplay();
}

void CHECK_FRAMEBUFFER_STATUS()
{                                                         
    GLenum status;
    status = glCheckFramebufferStatus(GL_DRAW_FRAMEBUFFER); 
    switch(status) {
    case GL_FRAMEBUFFER_COMPLETE:
        break;

    case GL_FRAMEBUFFER_UNSUPPORTED:
    /* choose different formats */
        break;

    default:
        /* programming error; will fail on all hardware */
        throw "Framebuffer Error";
    }
}

namespace render
{
    float const light_dir[]={1,1,1,0};
    float const light_color[]={1,0.95,0.9,1};

    void init()
    {
        glGenFramebuffers(1, &fb);
        glGenTextures(1, &color);
        glGenRenderbuffers(1, &depth);

        glBindFramebuffer(GL_FRAMEBUFFER, fb);

        glBindTexture(GL_TEXTURE_2D, color);
        glTexImage2D(   GL_TEXTURE_2D, 
                0, 
                GL_RGBA, 
                fbo_width, fbo_height,
                0, 
                GL_RGBA, 
                GL_UNSIGNED_BYTE, 
                NULL);

        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
        glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, color, 0);

        glBindRenderbuffer(GL_RENDERBUFFER, depth);
        glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT24, fbo_width, fbo_height);
        glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depth);

        CHECK_FRAMEBUFFER_STATUS();
    }

    void reshape(int width, int height)
    {
        render::width=width;
        render::height=height;
        aspect=float(width)/float(height);
        glutPostRedisplay();
    }

    void prepare()
    {
        static float a=0, b=0, c=0;

        glBindTexture(GL_TEXTURE_2D, 0);
        glEnable(GL_TEXTURE_2D);
        glBindFramebuffer(GL_FRAMEBUFFER, fb);

        glViewport(0,0,fbo_width, fbo_height);

        glClearColor(1,1,1,0);
        glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        gluPerspective(45, 1, 1, 10);

        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();

        glEnable(GL_LIGHT0);
        glEnable(GL_LIGHTING);

        glEnable(GL_DEPTH_TEST);
        glDisable(GL_CULL_FACE);

        glLightfv(GL_LIGHT0, GL_POSITION, light_dir);
        glLightfv(GL_LIGHT0, GL_DIFFUSE, light_color);

        glTranslatef(0,0,-5);

        glRotatef(a, 1, 0, 0);
        glRotatef(b, 0, 1, 0);
        glRotatef(c, 0, 0, 1);

        glutSolidTeapot(0.75);

        a=fmod(a+0.1, 360.);
        b=fmod(b+0.5, 360.);
        c=fmod(c+0.25, 360.);
    }

    void final()
    {
        static float a=0, b=0, c=0;

        glBindFramebuffer(GL_FRAMEBUFFER, 0);

        glViewport(0,0, width, height);

        glClearColor(1.,1.,1.,0.);
        glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        gluPerspective(45, aspect, 1, 10);

        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();
        glTranslatef(0,0,-5);

        glRotatef(b, 0, 1, 0);

        b=fmod(b+0.5, 360.);

        glEnable(GL_TEXTURE_2D);
        glBindTexture(GL_TEXTURE_2D, color);

        glEnable(GL_DEPTH_TEST);
        glEnable(GL_CULL_FACE);

        glEnable(GL_BLEND);
        glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

        glDisable(GL_LIGHTING);

        float cube[][5]=
        {
            {-1, -1, -1,  0,  0},
            { 1, -1, -1,  1,  0},
            { 1,  1, -1,  1,  1},
            {-1,  1, -1,  0,  1},

            {-1, -1,  1, -1,  0},
            { 1, -1,  1,  0,  0},
            { 1,  1,  1,  0,  1},
            {-1,  1,  1, -1,  1},
        };
        unsigned int faces[]=
        {
            0, 1, 2, 3,
            1, 5, 6, 2,
            5, 4, 7, 6,
            4, 0, 3, 7,
            3, 2, 6, 7,
            4, 5, 1, 0
        };

        glEnableClientState(GL_VERTEX_ARRAY);
        glEnableClientState(GL_TEXTURE_COORD_ARRAY);

        glVertexPointer(3, GL_FLOAT, 5*sizeof(float), &cube[0][0]);
        glTexCoordPointer(2, GL_FLOAT, 5*sizeof(float), &cube[0][3]);

        glCullFace(GL_BACK);
        glDrawElements(GL_QUADS, 24, GL_UNSIGNED_INT, faces);

        glCullFace(GL_FRONT);
        glDrawElements(GL_QUADS, 24, GL_UNSIGNED_INT, faces);

        glDisableClientState(GL_VERTEX_ARRAY);
        glDisableClientState(GL_TEXTURE_COORD_ARRAY);

    }

    void display()
    {
        prepare();
        final();

        glutSwapBuffers();
    }
}

仅供引用。