用OpenGL快速給圖形新增紋理含圓柱圓錐
阿新 • • 發佈：2019-02-01
這裡討論的是二維紋理
1.圖取影象資料
void readimage(char* filename, BYTE* imagedata)//所讀圖片均為24位bmp,且寬度補齊至四位元組邊界 { BITMAPFILEHEADER bf; //檔案頭 BITMAPINFOHEADER bi; //資訊頭 int m_ImageWidth; //圖象寬度 int m_ImageHeight; //圖象高度 FILE *fp1; //檔案指標，fp1為原始檔 //開啟檔案，到檔案指標 if ((fp1 = fopen(filename, "rb")) == NULL) { MessageBox(NULL, "檔案開啟錯誤", "warning", MB_OK); } fread((LPSTR)&bf, sizeof(BITMAPFILEHEADER), 1, fp1); //讀取檔案頭，讀取以後檔案指標在檔案頭末尾（即資訊頭） fread((LPSTR)&bi, sizeof(BITMAPINFOHEADER), 1, fp1); //讀取資訊頭 m_ImageWidth = bi.biWidth; //給圖象寬度賦值 m_ImageHeight = bi.biHeight; //給圖象高度賦值 fread(imagedata, m_ImageHeight*m_ImageWidth * 3, 1, fp1); //讀取圖象資料 fclose(fp1); }
注意：讀進來的影象為BGR,要調整為RGB
void adjustimage(BYTE* imagedata, int w, int h)
{
BYTE temp;
for (int i = 0; i<w*h; i++)
{<pre name="code" class="cpp">glEnable(GL_TEXTURE_2D);temp = imagedata[i * 3];imagedata[i * 3] = imagedata[i * 3 + 2];imagedata[i * 3 + 2] = temp;}} 2.設定紋理（因為一般要用到的紋理比較多，先將所有圖片讀入，要用到那張時候就使用glBindTexture函式來指定當前所使用的紋理物件）
注意：影象的畫素要與陣列對應，下面的是256*256
//------------------------設定紋理---------------------------------- void loadtexture() { glGenTextures(2, &texName);//2表示有兩個紋理 glBindTexture(GL_TEXTURE_2D, texName); { BYTE imagemoon[256][256][3]; //牆壁2的紋理 readimage("D:\\wall2.bmp", &imagemoon[0][0][0]); adjustimage(&imagemoon[0][0][0], 256, 256); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 256, 256, 0, GL_RGB, GL_UNSIGNED_BYTE, imagemoon); } { BYTE imagesky[256][256][3]; readimage("D:\\wall1.bmp", &imagesky[0][0][0]);//牆壁1的紋理 adjustimage(&imagesky[0][0][0], 256, 256); glBindTexture(GL_TEXTURE_2D, texName + 1); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, 256, 256, 0, GL_RGB, GL_UNSIGNED_BYTE, imagesky); } }
3.啟用紋理
glEnable(GL_TEXTURE_2D);例子：座標要對應，紋理用單位表示，（0.0，0.0）表示左下角（1.0,1.0）表示右上角
void display(void)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
//printf("At:%.2f %.2f %.2f\n",r*cos(c*du),h,r*sin(c*du)); //這就是視點的座標
glLoadIdentity();
gluLookAt(r*cos(c*du), h, r*sin(c*du), 0, 0, 0, 0, 1, 0); //從視點看遠點,y軸方向(0,1,0)是上方向
glColor3f(1.0f, 0.0f, 0.0f);
glEnable(GL_TEXTURE_2D);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
//地面
glPushMatrix();
glBindTexture(GL_TEXTURE_2D, texName + 2);
glColor3f(0.0, 1.0, 1.0);
glBegin(GL_QUADS);
glTexCoord2f(0.0, 0.0); glVertex3f(5.0f,-2.0f,3.0f);
glTexCoord2f(1.0, 0.0); glVertex3f(-5.0f, -2.0f, 3.0f);
glTexCoord2f(1.0, 1.0); glVertex3f(-5.0f, -2.0f, -3.0f);
glTexCoord2f(0.0, 1.0); glVertex3f(5.0f, -2.0f, -3.0f);
glEnd();
//左牆
glPushMatrix();
glBindTexture(GL_TEXTURE_2D, texName + 1);
glBegin(GL_POLYGON);
glTexCoord2f(0.0, 0.0); glVertex3f(-2.0, 0.0, 1.5);
glTexCoord2f(0.0, 0.66); glVertex3f(-2.0, 2.0, 1.5);
glTexCoord2f(0.5, 1.0); glVertex3f(-2.0, 3.0, 0.0);
glTexCoord2f(1.0, 0.66); glVertex3f(-2.0, 2.0, -1.5);
glTexCoord2f(1.0, 0.0); glVertex3f(-2.0, 0.0, -1.5);
glEnd();
glPopMatrix();
glFlush();
glutSwapBuffers();
glDisable(GL_TEXTURE_2D);
}5.對於圓柱和圓錐
將圓柱和圓錐看做是由很多線組成的，使用三角函式和一個迴圈就可以畫出
//圓柱
glTranslatef(-3.0, -2.0, 2.0);
glPushMatrix();
glBindTexture(GL_TEXTURE_2D, texName );
glBegin( GL_QUAD_STRIP);
double t = 0.0;double dt = 2*PI/nslice;
for (int j = 0; j <= nslice; ++j)
{
glTexCoord2f( t/(2*PI), 1.0); glVertex3f( cos( t), 2.0, -sin( t));
glTexCoord2f( t/(2*PI), 0.0); glVertex3f( cos( t), 0.0, -sin( t));
t = t + dt;
}
glEnd();
glPopMatrix();
//圓錐
glPushMatrix();
glBindTexture(GL_TEXTURE_2D, texName + 4 );
glBegin( GL_QUAD_STRIP);
double tt = 0.0;double dtt = 2*PI/nslice;
for (int j = 0; j <= nslice; ++j)
{
glTexCoord2f( tt/(2*PI), 1.0); glVertex3f( 0.0, 2.0, 0.0);
glTexCoord2f( tt/(2*PI), 0.0); glVertex3f( cos( tt), 0.0, -sin( tt));
tt = tt + dtt;
}
glEnd();
glPopMatrix();