通過 OpenGL 應用的紋理在渲染時不可見

Question

正如上面的標題所說，我嘗試使用 GLubyte 和 glTeximage 以及 glTexCoord2f 將棋盤樣式紋理應用到下面的 model，我之前應用了一個完美工作的材料，並且出於某種原因，我的紋理根本不會顯示，我似乎無法看到或弄清楚為什么，因為查看我正在遵循的示例，一切都應該正常工作。

視覺形象我應該擁有什么

#include <glut.h>


float angle[4];
float LightAngle;
bool LowerFrontLegDown = true;
bool LowerBackLegDown = true;


GLfloat corners[8][3] = { {-0.5,0.5,-0.5},{0.5,0.5,-0.5},
                        {0.5,-0.5,-0.5},{-0.5,-0.5,-0.5},
                        {-0.5,0.5,0.5},{0.5,0.5,0.5},
                        {0.5,-0.5,0.5},{-0.5,-0.5,0.5} };

//Two Dimensional Array for corners

GLfloat normals[][3] = { {0.0,0.0,1.0},
                                      {1.0,0.0,0.0},
                                      {0.0,-1.0,0.0},
                                      {0.0,1.0,0.0},
                                      {0.0,0.0,-1.0},
                                      {-1.0,0.0,0.0} };

typedef struct materialStruct {
    GLfloat ambient[4];
    GLfloat diffuse[4];
    GLfloat specular[4];
    GLfloat shininess;
};

materialStruct brassMaterial = {
       { 0.33, 0.22, 0.03, 1.00 },
       { 0.78, 0.57, 0.11, 1.00 },
       { 0.99, 0.91, 0.81, 1.00 },
       27.80 };

materialStruct redPlasticMaterial = {
       { 0.30, 0.00, 0.00, 1.00 },
       { 0.60, 0.00, 0.00, 1.00 },
       { 0.80, 0.60, 0.60, 1.00 },
       32.00 };


materialStruct* currentMaterial;

void setMaterial(materialStruct* materials) {
    glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT, materials->ambient);
    glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, materials->diffuse);
    glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR, materials->specular);
    glMaterialf(GL_FRONT_AND_BACK, GL_SHININESS, materials->shininess);
}

void drawFace(int a, int b, int c, int d) {
    glBegin(GL_POLYGON);
    glTexCoord2f(0.0, 0.0);
    glVertex3fv(corners[a]);
    glTexCoord2f(0.0, 1.0);
    glVertex3fv(corners[b]);
    glTexCoord2f(1.0, 1.0);
    glVertex3fv(corners[c]);
    glTexCoord2f(1.0, 0.0);
    glVertex3fv(corners[d]);
    glEnd();
} //Turns the corners from the two dimensional array into corner pieces for the model, allowing faces to be drawn

void ArrayCube() {
    glNormal3fv(normals[0]);
    drawFace(0, 3, 2, 1);
    glNormal3fv(normals[1]);
    drawFace(3, 0, 4, 7);
    glNormal3fv(normals[2]);
    drawFace(2, 3, 7, 6);
    glNormal3fv(normals[3]);
    drawFace(1, 2, 6, 5);
    glNormal3fv(normals[4]);
    drawFace(4, 5, 6, 7);
    glNormal3fv(normals[5]);
    drawFace(5, 4, 0, 1);
}
//Draws the faces of the model and creates a cube we can call later for the individual parts of the model.

void rotate() {

    angle[0] += 1.0;
    if (angle[0] > 360) angle[0] -= 360;

    if (LowerFrontLegDown) angle[1] -= 0.2;
    else angle[1] += 0.2;

    if (angle[1] < 315) LowerFrontLegDown = false;
    if (angle[1] > 360) LowerFrontLegDown = true;

    angle[0] += 1.0;
    if (angle[0] > 360) angle[0] -= 360;

    if (LowerBackLegDown) angle[1] -= 0.2;
    else angle[1] += 0.2;

    if (angle[1] < 315) LowerBackLegDown = false;
    if (angle[1] > 360) LowerBackLegDown = true;

    glutPostRedisplay();
}






void MainBody()
{
    glPushMatrix();
    glScalef(1.25, 0.25, 0.5);
    ArrayCube();
    glPopMatrix();
}

void LowerNeck()
{
    glPushMatrix();
    glTranslatef(0.5, 0.25, 0);
    glScalef(0.15, 0.5, 0.15);
    ArrayCube();
    glPopMatrix();
}

void UpperNeck()
{
    glPushMatrix();
    glTranslatef(0.5, 0.75, 0);
    glScalef(0.15, 0.5, 0.15);
    ArrayCube();
    glPopMatrix();
}

void Head()
{
    glPushMatrix();
    glRotatef(90, 0.0, 0.0,1.0);
    glTranslatef(1, -0.6, 0);
    glScalef(0.1, 0.4, 0.15);
    ArrayCube();
    glPopMatrix();
}

void RightHorn()
{
    glPushMatrix();
    glRotatef(0, 0.0, 0.0,1);
    glTranslatef(0.5, 1.15, 0.035);
    glScalef(0.05, 0.15, 0.05);
    ArrayCube();
    glPopMatrix();
}

void LeftHorn()
{
    glPushMatrix();
    glRotatef(0, 0.0, 0.0, 1);
    glTranslatef(0.5, 1.15, -0.035);
    glScalef(0.05, 0.15, 0.05);
    ArrayCube();
    glPopMatrix();
}

void FrontUpperRightLeg()
{
    glPushMatrix();
    glTranslatef(0.5, -0.35, 0.15);
    glScalef(0.15, 0.5, 0.15);
    ArrayCube();
    glPopMatrix();
}

void FrontLowerRightLeg()
{
    glPushMatrix();
 
    glTranslatef(0.5, -0.75, 0.15);
    glRotatef(angle[1], 0.0, 0.0, 1.0);
    glScalef(0.15, 0.5, 0.15);
    ArrayCube();
    glPopMatrix();
}

void FrontUpperLeftLeg()
{
    glPushMatrix();
    glTranslatef(0.5, -0.35, -0.15);
    glScalef(0.15, 0.5, 0.15);
    ArrayCube();
    glPopMatrix();
}

void FrontLowerLeftLeg()
{
    glPushMatrix();
    glTranslatef(0.5, -0.75, -0.15);
    glRotatef(angle[1], 0.0, 0.0, 1.0);
    glScalef(0.15, 0.5, 0.15);
    ArrayCube();
    glPopMatrix();
}

void BackUpperRightLeg()
{
    glPushMatrix();
    glTranslatef(-0.5, -0.35, -0.15);
    glScalef(0.15, 0.5, 0.15);
    ArrayCube();
    glPopMatrix();
}

void BackLowerRightLeg()
{
    glPushMatrix();
    glTranslatef(-0.5, -0.75, -0.15);
    glRotatef(angle[1], 0.0, 0.0, 1.0);
    glScalef(0.15, 0.5, 0.15);
    ArrayCube();
    glPopMatrix();
}

void BackUpperLeftLeg()
{
    glPushMatrix();
    glTranslatef(-0.5, -0.35, 0.15);
    glScalef(0.15, 0.5, 0.15);
    ArrayCube();
    glPopMatrix();
}

void BackLowerLeftLeg()
{
    glPushMatrix();
    glTranslatef(-0.5, -0.75, 0.15);
    glRotatef(angle[1], 0.0, 0.0, 1.0);
    glScalef(0.15, 0.5, 0.15);
    ArrayCube();
    glPopMatrix();
}

void Tail()
{
    glPushMatrix();
    glTranslatef(-0.65, -0.25, 0);
    glScalef(0.05, 0.75, 0.05);
    ArrayCube();
    glPopMatrix();
}

//Each of the below functions draws an individual part of the whole model and places those parts where they need to go once the program runs

void DrawGiraffe()
{
    MainBody();
    LowerNeck();
    UpperNeck();
    Head();
    RightHorn();
    LeftHorn();
    FrontUpperRightLeg();
    FrontLowerRightLeg(); 
    FrontUpperLeftLeg();
    FrontLowerLeftLeg();
    BackUpperRightLeg();
    BackLowerRightLeg();
    BackUpperLeftLeg();
    BackLowerLeftLeg();
    Tail();

}

//Calls the above functions to render the final model

//The rotate function allows the camera to rotate around the model

void display() {
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    gluLookAt(0.6, 0.6, 0.6, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);

    DrawGiraffe();
    glutSwapBuffers();
}


void init() {
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_TEXTURE_2D);
    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);
    currentMaterial = &redPlasticMaterial;
    setMaterial(currentMaterial);
    glColor3f(1.0, 1.0, 1.0);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(-1.0, 1.0, -1.0, 1.0, -1.0, 2.5);
    GLfloat light_pos[] = {2.0,2.0,2.0, 1.0};
    glLightfv(GL_LIGHT0, GL_POSITION, light_pos);     
}

int main(int argc, char** argv) 
{
    angle[0] = 0;
    angle[1] = 360;
    angle[2] = 315;
    angle[3] = 0;

        GLubyte image[64][64][3];
    int i, j, r, c;
    for(i = 0;i < 64; i++){
          for(j = 0;j < 64; j++){
                c = ((((i&0x8)== 0)^((j&0x8))==0))*255;
                image[i][j][0] = (GLubyte) c;
                image[i][j][1] = (GLubyte) c;
                image[i][j][2] = (GLubyte) c;
          }
    }

    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 64, 64, 0, GL_RGB, GL_UNSIGNED_BYTE, image);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);

    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
    glutInitWindowSize(500, 500);
    glutInitWindowPosition(0, 0);
    glutCreateWindow("Giraffe");
    glutDisplayFunc(display);
    glutIdleFunc(rotate);
    init();
    glutMainLoop();
}

Answer 1

您的代碼有很多問題。

1：您使用的是glTexParameterf而不是glTexParameteri 。

2：您沒有綁定紋理 object，這意味着對glTexImage2D function 的調用將毫無用處，因為glTexImage2D依賴於GL_TEXTURE_2D的有界紋理。

3：在調用glut初始化函數之前，您正在初始化紋理。 這意味着對 OpenGL 函數的任何調用都將毫無用處。

你應該用這樣的東西初始化你的紋理

// this should be declared as a global variable
GLuint texture;


glGenTextures(1, &texture); 
glBindTexture(GL_TEXTURE_2D, texture);

GLubyte image[64][64][3];
int i, j, r, c;
for(i = 0;i < 64; i++){
    for(j = 0;j < 64; j++){
          c = ((((i&0x8)== 0)^((j&0x8))==0))*255;
          image[i][j][0] = (GLubyte) c;
          image[i][j][1] = (GLubyte) c;
          image[i][j][2] = (GLubyte) c;
    }
}
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 64, 64, 0, GL_RGB, GL_UNSIGNED_BYTE, image);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);

並將紋理的初始化移動到init function，就在調用glEnable(GL_TEXTURE_2D);

當然，你需要在渲染的時候通過調用glBindTexture(GL_TEXTURE_2D, texture);來綁定這個紋理。