在同一屏幕上显示两个不同的对象

Question

我试图在同一个屏幕上显示一个球体和一个圆环，但似乎“glutInitDisplayMode”是导致我只显示一个的原因。当我把它保持为glutInitDisplayMode(GLUT_SINGLE | GLUT_RGBA |GLUT_DEPTH)时，圆环显示。

当我把它保持为glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH)球体显示。我可以做什么来展示它们？

渲染代码如下：

static void render(void) {

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glMatrixMode(GL_MODELVIEW);
    // clear the drawing buffer.
    glClear(GL_COLOR_BUFFER_BIT);
    // clear the identity matrix.
    glLoadIdentity();
    glTranslatef(0.0, 0.0, -5.0);
    glColor3f(0.0, 0.0, 0.0);
    glRotatef(zRotated, 0.0, 0.0, 1.0);
    // scaling transfomation 
    glScalef(1.0, 1.0, 1.0);
    // built-in (glut library) function , draw you a sphere.
    glutSolidTorus(innerRadius, outerRadius, sides, rings);
    // Flush buffers to screen

    glFlush();

  // glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

   // activate our shader program
    glUseProgram(programId);

   // turn on depth buffering
   glEnable(GL_DEPTH_TEST);

   float aspectRatio = (float)width / (float)height;
   glm::mat4 projection = glm::perspective(glm::radians(45.0f), aspectRatio, 0.1f, 1000.0f);


   // view matrix - orient everything around our preferred view
   glm::mat4 view = glm::lookAt(
      glm::vec3(40,30,30), // eye/camera location
      glm::vec3(0,0,0),    // where to look
      glm::vec3(0,1,0)     // up
   );

   // model matrix: translate, scale, and rotate the model
   glm::vec3 rotationAxis(0,1,0);
   glm::mat4 model = glm::mat4(1.0f);
   model = glm::rotate(model, glm::radians(angle), glm::vec3(0, 1, 0)); // rotate about the y-axis
   model = glm::scale(model, glm::vec3(25.0f, 25.0f, 25.0f));

   // model-view-projection matrix
   glm::mat4 mvp = projection * view * model;
   GLuint mvpMatrixId = glGetUniformLocation(programId, "MVP");
   glUniformMatrix4fv(mvpMatrixId, 1, GL_FALSE, &mvp[0][0]);

   // texture sampler - a reference to the texture we've previously created
   // send the texture id to the texture sampler
   GLuint textureUniformId = glGetUniformLocation(programId, "textureSampler");
   glActiveTexture(GL_TEXTURE0);
   glBindTexture(GL_TEXTURE_2D, textureId);
   glUniform1i(textureUniformId, 0);

   // find the names (ids) of each vertex attribute
   GLint positionAttribId = glGetAttribLocation(programId, "position");
   GLint colourAttribId = glGetAttribLocation(programId, "colour");
   GLint textureCoordsAttribId = glGetAttribLocation(programId, "textureCoords");
   GLint normalAttribId = glGetAttribLocation(programId, "normal");

   // provide the vertex positions to the shaders
   glBindBuffer(GL_ARRAY_BUFFER, positions_vbo);
   glEnableVertexAttribArray(positionAttribId);
   glVertexAttribPointer(positionAttribId, 3, GL_FLOAT, GL_FALSE, 0, nullptr);

   // provide the vertex texture coordinates to the shaders
   glBindBuffer(GL_ARRAY_BUFFER, textureCoords_vbo);
   glEnableVertexAttribArray(textureCoordsAttribId);
   glVertexAttribPointer(textureCoordsAttribId, 2, GL_FLOAT, GL_FALSE, 0, nullptr);

   // provide the vertex normals to the shaders
   glBindBuffer(GL_ARRAY_BUFFER, normals_vbo);
   glEnableVertexAttribArray(normalAttribId);
   glVertexAttribPointer(normalAttribId, 3, GL_FLOAT, GL_FALSE, 0, nullptr);

    // draw the triangles
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexBuffer);
    glDrawElements(GL_TRIANGLES, numVertices, GL_UNSIGNED_INT, (void*)0);

    // disable the attribute arrays
   glDisableVertexAttribArray(positionAttribId);
   glDisableVertexAttribArray(textureCoordsAttribId);
   glDisableVertexAttribArray(normalAttribId);
   glDisableVertexAttribArray(colourAttribId);

    // make the draw buffer to display buffer (i.e. display what we have drawn)
    glutSwapBuffers(); 
}

Answer 1

glutSolidTorus通过使用固定的函数属性绘制圆环。对于这个兼容性配置文件OpenGL Context不可或缺。

glutSolidTorus与您的着色器程序不兼容。在glutSolidTorus之前使当前安装的程序无效：

glUseProgram(0);
glutSolidTorus(innerRadius, outerRadius, sides, rings);

注意，OpenGL是一个状态引擎。如果安装了某个程序，则会保留该程序，直到安装了另一个程序或该程序无效，甚至超出了框架。在你的情况下，第一帧中的问题不是问题，但是当调用glutSolidTorus时，它仍将安装在第2帧的开头。

如果您使用的是双缓冲窗口（GLUT_DOUBLE），则必须调用glutSwapBuffers。 glutSwapBuffers交换缓冲区。窗口中显示了绘制的缓冲区。显示窗口的缓冲区准备在下一帧中绘制。

在单个缓冲窗口中，您可以执行glFlush。这迫使OpenGL完成绘图。由于绘制到的缓冲区是相同的，它显示在窗口上，这导致绘制到缓冲区的所有内容立即显示在窗口中。

将歌手qazxsw poi从qazxsw poi函数的中间调用到它的结尾，就在glFlush之前：

render