CODEWITHSUNDEEP
c++openglperspectivecameraorthographic
ram
ram

Reputation: 124

Modern Opengl: Simultaneous orthographic and perspective projection

I am trying to display two cubes using modern opengl (https://preview.ibb.co/hif8t6/Screenshot_2017_10_31_09_59_27.png). The first cube is displayed by orthographic projection (left) and the second by perspective projection (right). That is working fine but i am unable to get the left cube to go behind the right cube. Here is the relavant snippet of code

    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);

What do i do to get the cube with orthographic projection to go behind the cube with perspective projection?

Upvotes: 0

Views: 442

Answers (1)

Eric
Eric

Reputation: 7

I'm not a OpenGL programmer but this is what I think.

You are drawing the object twice using the glDrawArrays lines. For the projection matrices they are using your orthographic and perspective matrices.

However these matrices are created using different parameters:

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));

My guess is that you want to unify the translation parameters so that the cubes lie exactly on top of each other.

E.g.

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));

Upvotes: -2

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