在同一屏幕上显示两个不同的对象

Question

我试图在同一屏幕上显示一个球体和一个环面，但 "glutInitDisplayMode" 似乎是导致我只显示一个的原因。当我将它保持为 glutInitDisplayMode(GLUT_SINGLE | GLUT_RGBA |GLUT_DEPTH) 时，圆环显示。

当我将其保持为 glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH) 时，球体会显示。我该怎么做才能显示两者？

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 draws a torus, by the use of the fixed function attributes. For this a compatibility profile OpenGL Context缺一不可。

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

之前

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

请注意，OpenGL 是一个状态引擎。如果安装了一个程序，它会一直保留，直到安装另一个程序或它失效，甚至超出框架。在你的情况下，第一帧不是问题，但它仍会安装在第二帧的开头，当 glutSolidTorus 被调用时。

如果您使用双缓冲 window (GLUT_DOUBLE)，则必须调用 glutSwapBuffers。 glutSwapBuffers 交换缓冲区。 window 中显示的缓冲区。 show int eh window 缓冲区已准备好在下一帧中绘制。

在单个缓冲中 window 你可以做到 glFlush。这会强制 OpenGL 完成绘图。由于绘制到的缓冲区与显示在 window 上的相同，这导致绘制到缓冲区的所有内容立即显示在 window.

中

将 glFlush 调用从 render 函数的中间移动到它的末尾，就在 glutSwapBuffers:

之前

void render()
{
    // ...

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

    // glFlush(); <---- delete

    // ...

    glUseProgram(programId);

    // ...

    glDrawElements(GL_TRIANGLES, numVertices, GL_UNSIGNED_INT, (void*)0);

    // ...

    glFlush();
    glutSwapBuffers(); 
}

在同一屏幕上显示两个不同的对象

Displaying two different objects on same screen

c++

opengl

glut

glm-math

opengl-compat