Question

以下是README所说的示例：“使用旋转灯在一个多边形上凹凸贴图”。让我补充一点：多边形是一个正方形，其上的凹凸贴图应该在原始多边形正方形内产生一个凸起的正方形。 main（）中第二个'for'循环中的i和j（像素迭代）的值表示该内部正方形图案。

问题：当我运行它时，显示窗口出现但是它是空白。也许您可以尝试自己运行它：如果它有效，让我们在设置中找到差异;如果它，请不要帮助找到代码的错误。代码在这里：http://www.cs.unm.edu/~angel/BOOK/INTERACTIVE_COMPUTER_GRAPHICS/SIXTH_EDITION/。单击“代码”，然后单击“第07条/”。这是例子7.3。另外，下面是参考代码。注意：我在fshader73.glsl中添加了“#version 150”以在运行时删除版本错误。

example3.cpp ：

/* sets up flat mesh */
/* sets up elapsed time parameter for use by shaders */

#include "Angel.h"

#define N 256

GLfloat normals[N][N][3];
GLuint         program;
GLuint        texMapLocation;
GLfloat tangent[3] = {1.0, 0.0, 0.0};

typedef Angel::vec4  point4;
typedef Angel::vec4  color4;

point4 points[6];
vec2 tex_coord[6];
mat4 ctm, projection;

vec4 normal = point4(0.0, 1.0, 0.0, 0.0);
color4 light_diffuse = color4(1.0, 1.0, 1.0, 1.0);
color4 material_diffuse = color4(0.7, 0.7, 0.7, 1.0);
point4  light_position = point4(0.0, 10.0, 0.0, 1.0);
vec4 eye =  vec4(2.0, 2.0, 2.0, 1.0);
vec4 at = vec4(0.5, 0.0, 0.5, 1.0);
vec4 up = vec4(0.0, 1.0, 0.0, 1.0);



GLuint loc, loc2;
GLuint buffers[2];

GLuint normal_loc;
GLuint diffuse_product_loc;
GLuint light_position_loc;
GLuint ctm_loc, projection_loc;
GLuint tangent_loc;


/* standard OpenGL initialization */

vec4 product(vec4 a, vec4 b)
{
  return vec4(a[0]*b[0], a[1]*b[1], a[2]*b[2], a[3]*b[3]);
}
static void init()
{
    const float meshColor[]     = {0.7f, 0.7f, 0.7f, 1.0f}; 

    glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, meshColor);

    glClearColor(1.0f, 1.0f, 1.0f, 1.0f);

    glBindTexture(GL_TEXTURE_2D, 0);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, N, N, 0, GL_RGB, GL_FLOAT, normals);
    glEnable(GL_TEXTURE_2D);


    glEnable(GL_DEPTH_TEST);

   loc = glGetAttribLocation(program, "vPosition");
   glEnableVertexAttribArray(loc);
   glVertexAttribPointer(loc, 4, GL_FLOAT, GL_FALSE, 0, points);

   loc2 = glGetAttribLocation(program, "texcoord");
   glEnableVertexAttribArray(loc2);
   glVertexAttribPointer(loc2, 2, GL_FLOAT, GL_FALSE, 0, tex_coord);

   glGenBuffers(2, buffers);
   glBindBuffer(GL_ARRAY_BUFFER, buffers[0]);
   glBufferData(GL_ARRAY_BUFFER, sizeof(points), points, GL_STATIC_DRAW);

   tangent_loc = glGetUniformLocation(program, "objTangent");
   glUniform3fv(tangent_loc, 3, tangent);

   normal_loc = glGetUniformLocation(program, "Normal");
   glUniform4fv(normal_loc, 4, normal);

   vec4 diffuse_product = product(light_diffuse, material_diffuse);
   diffuse_product_loc = glGetUniformLocation(program, "DiffuseProduct");
   glUniform4fv(diffuse_product_loc, 4, diffuse_product);

   light_position_loc = glGetUniformLocation(program, "LightPosition");
   glUniform4fv(light_position_loc, 4, light_position);

   ctm_loc = glGetUniformLocation(program, "ModelView");
   ctm = LookAt(eye, at , up);
   glUniformMatrix4fv(ctm_loc, 16, GL_TRUE, ctm);

   mat4 nm;
   GLfloat det;
   det = ctm[0][0]*ctm[1][1]*ctm[2][2]+ctm[0][1]*ctm[1][2]*ctm[2][1]
     -ctm[2][0]*ctm[1][1]*ctm[0][2]-ctm[1][0]*ctm[0][1]*ctm[2][2]-ctm[0][0]*ctm[1][2]*ctm[2][1];
   nm[0][0] = (ctm[1][1]*ctm[2][2]-ctm[1][2]*ctm[2][1])/det;
   nm[0][1] = -(ctm[0][1]*ctm[2][2]-ctm[0][2]*ctm[2][1])/det;
   nm[0][2] = (ctm[0][1]*ctm[2][0]-ctm[2][1]*ctm[2][2])/det;
   nm[1][0] = -(ctm[0][1]*ctm[2][2]-ctm[0][2]*ctm[2][1])/det;
   nm[1][1] = (ctm[0][0]*ctm[2][2]-ctm[0][2]*ctm[2][0])/det;
   nm[1][2] = -(ctm[0][0]*ctm[2][1]-ctm[2][0]*ctm[0][1])/det;
   nm[2][0] = (ctm[0][1]*ctm[1][2]-ctm[1][1]*ctm[0][2])/det;
   nm[2][1] = -(ctm[0][0]*ctm[1][2]-ctm[0][2]*ctm[1][0])/det;
   nm[2][2] = (ctm[0][0]*ctm[1][1]-ctm[1][0]*ctm[0][1])/det;

    GLuint nm_loc;
    nm_loc = glGetUniformLocation(program, "NormalMatrix");
    glUniformMatrix4fv(nm_loc, 16, GL_TRUE, nm);

    projection_loc = glGetUniformLocation(program, "Projection");
    projection = Ortho(-0.75,0.75,-0.75,0.75,-5.5,5.5);
    glUniformMatrix4fv(projection_loc, 16, GL_TRUE, projection);

    texMapLocation = glGetUniformLocation(program, "texMap");

}

    /* set up uniform parameter */

void mesh()
{
      point4 vertices[4] = {point4(0.0, 0.0, 0.0, 1.0), point4(1.0, 0.0, 0.0, 1.0),
         point4(1.0, 0.0, 1.0, 1.0), point4(0.0, 0.0, 1.0, 1.0)};

       points[0] = vertices[0];
       tex_coord[0] = vec2(0.0, 0.0);
       points[1] = vertices[1];
       tex_coord[1] = vec2(1.0, 0.0);
       points[2] = vertices[2];
       tex_coord[2] = vec2(1.0, 1.0);
       points[3] = vertices[2];
       tex_coord[3] = vec2(1.0, 1.0);
       points[4] = vertices[3];
       tex_coord[4] = vec2(0.0, 1.0);
       points[5] = vertices[0];
       tex_coord[5] = vec2(0.0, 0.0);
}

static void draw()
{

    glUniform1i(texMapLocation, 0);

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    mesh(); 

    glDrawArrays(GL_TRIANGLES, 0, 6);

    glutSwapBuffers();
}

static void reshape(int w, int h)
{
    glViewport(0, 0, w, h);
    glutPostRedisplay();
}

static void keyboard(unsigned char key, int x, int y)
{
    switch (key) {
    case 27:
    case 'Q':
    case 'q':
        exit(EXIT_SUCCESS);
    }
}

void idle()
{
   int t;
   t = glutGet(GLUT_ELAPSED_TIME);
   light_position[0] = 5.5*sin(0.001*t);
   light_position[2] = 5.5*cos(0.001*t);
   glUniform4fv(light_position_loc, 4, light_position);
   glutPostRedisplay();
}

int main(int argc, char** argv)
{
    int i,j, k;
    float d;

    float data[N+1][N+1];
    for(i=0;i<N+1;i++) for(j=0;j<N+1;j++) data[i][j]=0.0;
    for(i=N/4; i< 3*N/4; i++) for(j=N/4;j<3*N/4;j++) data[i][j] = 1.0;

    for(i=0;i<N;i++) for(j=0;j<N;j++)
    {
       normals[i][j][0] = data[i][j]-data[i+1][j];
       normals[i][j][2] = data[i][j]-data[i][j+1];
       normals[i][j][1]= 1.0;
    }


    for(i=0;i<N;i++) for(j=0;j<N;j++)
    {
       d = 0.0;
       for(k=0;k<3;k++) d+=normals[i][j][k]*normals[i][j][k];
       d=sqrt(d);
       for(k=0;k<3;k++) normals[i][j][k]= 0.5*normals[i][j][k]/d+0.5;
    }

    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_DEPTH);
    glutInitWindowSize(1024, 1024);

    glutInitContextVersion( 3, 2 );
    glutInitContextProfile( GLUT_CORE_PROFILE );

    glutCreateWindow("Simple GLSL example");
    glutDisplayFunc(draw);
    glutReshapeFunc(reshape);
    glutKeyboardFunc(keyboard);
    glutIdleFunc(idle);

    glewInit();

    program = InitShader("vshader73.glsl", "fshader73.glsl");
    init();


    glutMainLoop();
    return 0;
}

vshader73.glsl ：

/* bump map vertex shader */

#version 150

out vec3 L; /* light vector in texture-space coordinates */
out vec3 V; /* view vector in texture-space coordinates */

in vec2 texcoord;
in vec4 vPosition;

uniform vec4 Normal;
uniform vec4 LightPosition;
uniform mat4 ModelView;
uniform mat4 Projection;
uniform mat4 NormalMatrix;
uniform vec3 objTangent; /* tangent vector in object coordinates */

out vec2 st;

void main()
{
    mat3 NM3;

    NM3[0][0] = NormalMatrix[0][0];
    NM3[0][1] = NormalMatrix[0][1];
    NM3[0][2] = NormalMatrix[0][2];
    NM3[1][0] = NormalMatrix[1][0];
    NM3[1][1] = NormalMatrix[1][1];
    NM3[1][2] = NormalMatrix[1][2];
    NM3[2][0] = NormalMatrix[2][0];
    NM3[2][1] = NormalMatrix[2][1];
    NM3[2][2] = NormalMatrix[2][2];

    gl_Position = Projection*ModelView*vPosition;


    st = texcoord;

    vec3 eyePosition = vec3(ModelView*vPosition);
    vec3 eyeLightPos = LightPosition.xyz;

   /* normal, tangent and binormal in eye coordinates */

    vec3 N = normalize(NM3*Normal.xyz);
    vec3 T  = normalize(NM3*objTangent);
    vec3 B = cross(N, T);

    /* light vector in texture space */

    L.x = dot(T, eyeLightPos-eyePosition);
    L.y = dot(B, eyeLightPos-eyePosition);
    L.z = dot(N, eyeLightPos-eyePosition);

    L = normalize(L);

    /* view vector in texture space */

    V.x = dot(T, -eyePosition);
    V.y = dot(B, -eyePosition);
    V.z = dot(N, -eyePosition);

    V = normalize(V);
}

fshader73.glsl ：

#version 150

in vec3 L;
in vec3 V;
uniform sampler2D texMap;
in vec2 st;
uniform vec4 DiffuseProduct;

out vec4 fColor;

void main()
{

   vec4 N = texture2D(texMap, st);
   vec3 NN =  normalize(2.0*N.xyz-1.0);
   vec3 LL = normalize(L);
   float Kd = max(dot(NN.xyz, LL), 0.0);
   fColor = Kd*DiffuseProduct;
}

修改：

根据Brett的评论，我用以下内容替换了glBindTexture(GL_TEXTURE_2D, 0) - 仍然是一个空白的白色窗口：

GLuint texture;
glGenTextures( 1, &texture );
glBindTexture(GL_TEXTURE_2D, texture);
...
glActiveTexture(GL_TEXTURE0);

Answer 1

我的评论超出了角色的限制，所以希望这值得回答。

我唯一能看到的问题可能是你的glUniformMatrix4fv电话。根据{{3}}，第二个参数将其描述为要更改的矩阵数。 3.2核心参考页面未在其网站上链接，因此我无法查找该特定上下文。因此对于glUniformMatrix4fv(projection_loc, 16, GL_TRUE, projection);，它打算在一个名为“Projection”的数组中找到16个矩阵，但是你只定义了uniform mat4 Projection;。这可能是也可能不是你问题的一部分，而且我甚至可能不正确，特别是如果这是其他人编译/使用的已知教程。

此外，glEnable（GL_TEXTURE_2D）不需要（OpenGl 4 language reference），其OpenGL上下文版本为3.2核心，在此设置：

glutInitContextVersion( 3, 2 );
glutInitContextProfile( GLUT_CORE_PROFILE );

如果编译器没有给您任何错误，请尝试在您认为可能有问题的行之后添加glGetError()。返回值映射到OpenGL头文件中的枚举值（or even usable, i think?将列出它们），我认为文档也会列出它们。

除此之外，您可能只想检查“normals”三维数组是否按照您期望的方式在内存中进行布局，因为我从未尝试过手动构建数组以用作纹理自己（虽然图像基本上都是字节数据的字符串，所以在这种情况下我不知道它是怎么回事。）

希望这有助于您，或者至少指出您正确的方向。祝你好运。

编辑＃1 ：我意识到我对着色器检查的评论不是很完整，因为我没有提到一些API调用。这是一个例子：

      char * dataBuffer;
      struct _stat fileStat;
      long fLen;
      FILE * vSh;
      FILE * fSh;
      int desc;

      GLint status;
      GLint logLength;

      GLuint vShader = glCreateShader(GL_VERTEX_SHADER);
      //errort = glGetError();
      GLuint fShader = glCreateShader(GL_FRAGMENT_SHADER);
      GLuint program = glCreateProgram();
      /*__________________________________________________*/

      vSh = fopen("vShader.vSh", "r");
      desc = _fileno(vSh);
      _fstat(desc, &fileStat);

      fLen = fileStat.st_size;

      dataBuffer = (char *) calloc((fLen + 1), sizeof(char));
      if (dataBuffer == NULL)
      {
            MessageBox(NULL, "Malloc failure: VS", "Create Program", MB_OK | MB_ICONINFORMATION);
            return 1;
      }


      if(feof(vSh) == 0)
      {
            MessageBox(NULL, "Did not reach EoF for VS", "Create Program", MB_OK | MB_ICONINFORMATION);
            return 2;
      }
      fclose(vSh);

      glShaderSource(vShader, 1, &dataBuffer, NULL);
      glCompileShader(vShader);

      //Error checking
      glGetShaderiv(vShader, GL_COMPILE_STATUS, &status);
      if (status == GL_FALSE)
      {
            glGetShaderiv(vShader, GL_INFO_LOG_LENGTH, &logLength);
            char resultV[logLength+1];
            glGetShaderInfoLog(vShader, logLength, NULL, resultV);

            MessageBox(NULL, resultV, "Vertex Compile Error", MB_OK);
      }
      free(dataBuffer);

我获取着色器的方式并不是真正重要的部分，所以希望这并不会让你感到困惑。当谈到检查着色器是否存在错误时，标记为//Error checking的部分就是我的意思。

Answer 2

Alex我的朋友你很亲密！基本上，只有glUniform...个glUniformMatrix...来1进行调用，需要{{1}}作为第二个参数。

GL＆amp; GLSL：凹凸贴图：这个教科书示例有什么问题？

2 个答案: