现代Opengl:同时正投影和透视投影

Question

我正在尝试使用现代opengl显示两个立方体(https://preview.ibb.co/hif8t6/Screenshot_2017_10_31_09_59_27.png)。第一个立方体通过正交投影(左)显示，第二个立方体通过透视投影(右)显示。这很好，但我无法让左立方体在右立方体后面。这是代码的相关片段

ourShader_ortho.Use();
ourShader_persp.Use();
glm::mat4 model_ortho, model1, model2, model;
glm::mat4 view_ortho, view_persp;
glm::mat4 orthographic;
glm::mat4 perspective;
model1 = glm::rotate(model, (GLfloat)glfwGetTime()*1.0f, glm::vec3(0.5f, 1.0f, 0.0f));
model2 = glm::rotate(model, (GLfloat)glfwGetTime()*1.0f, glm::vec3(0.0f, 1.0f, 0.5f));
model = model1 * model2;
view_ortho = glm::translate(view_ortho, glm::vec3(200.0f, 200.0f, -150.0f));
orthographic = glm::ortho(0.0f, (GLfloat)width, 0.0f, (GLfloat)height, 0.1f, 200.0f);
view_persp = glm::translate(view_persp, glm::vec3(1.0f, 0.0f, -3.0f));
perspective = glm::perspective(45.0f, (GLfloat)width/(GLfloat)height, 0.1f, 200.0f);
GLint modelLoc_ortho = glGetUniformLocation(ourShader_ortho.Program, "model");
GLint viewLoc_ortho = glGetUniformLocation(ourShader_ortho.Program, "view");
GLint projLoc_ortho = glGetUniformLocation(ourShader_ortho.Program, "orthographic");
glUniformMatrix4fv(modelLoc_ortho, 1, GL_FALSE, glm::value_ptr(model_ortho));
glUniformMatrix4fv(viewLoc_ortho, 1, GL_FALSE, glm::value_ptr(view_ortho));
glUniformMatrix4fv(projLoc_ortho, 1, GL_FALSE, glm::value_ptr(orthographic));   
glBindVertexArray(VAO_O);
glDrawArrays(GL_TRIANGLES, 0, 6);
glBindVertexArray(0);
GLint modelLoc_persp = glGetUniformLocation(ourShader_persp.Program, "model");
GLint viewLoc_persp = glGetUniformLocation(ourShader_persp.Program, "view");
GLint projLoc_persp = glGetUniformLocation(ourShader_persp.Program, "perspective");
glUniformMatrix4fv(modelLoc_persp, 1, GL_FALSE, glm::value_ptr(model));
glUniformMatrix4fv(viewLoc_persp, 1, GL_FALSE, glm::value_ptr(view_persp));
glUniformMatrix4fv(projLoc_persp, 1, GL_FALSE, glm::value_ptr(perspective));    
glBindVertexArray(VAO_P);
glDrawArrays(GL_TRIANGLES, 0, 36);
glBindVertexArray(0);

我该怎么做才能让正投影的立方体在透视投影的立方体后面？

Answer 1

我不是OpenGL程序员，但这就是我的想法。

使用glDrawArrays线绘制对象两次。对于投影矩阵，他们使用的是orthographic和perspective矩阵。

然而，这些矩阵是使用不同的参数创建的：

view_ortho = glm::translate(view_ortho, glm::vec3(200.0f, 200.0f, -150.0f));
view_persp = glm::translate(view_persp, glm::vec3(1.0f, 0.0f, -3.0f));

我的猜测是，你想统一翻译参数，使立方体正好位于彼此的顶部。

例如

view_ortho = glm::translate(view_ortho, glm::vec3(200.0f, 200.0f, -150.0f));
view_persp = glm::translate(view_persp, glm::vec3(200.0f, 200.0f, -150.0f));