我正在学习opengl,目前我正在与VAO拼搏。 我想用VAO画一个立方体和一个三角形,但不幸的是,只绘制了我以后创建的对象。这是我做的主循环:Opengl VAO被覆盖
void main()
{
//loading shader, generate window, etc ...
//generate a cube:
GLuint cube_vao = generateCube();
//next, generate a triangle:
GLuint triangle_vao = generateTriangle();
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LESS);
// Clear the screen
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
do
{
//draw:
glBindVertexArray(triangle_vao);
glDrawArrays(GL_TRIANGLES, 0, 3);
glBindVertexArray(cube_vao);
glDrawArrays(GL_TRIANGLES, 0, 12*3);
glfwPollEvents();
glfwSwapBuffers(window);
} while (glfwGetKey(window, GLFW_KEY_ESCAPE) != GLFW_PRESS &&
glfwWindowShouldClose(window) == 0);
}
两者generateCube()
和generateTriangle()
基本上做同样的事情:创造顶点,创建VBO,创建VAO并设置属性。然后他们返回vao id。 这是generateTriangle()
例如:
generateTriangle()
{
//generate the vertex positions:
GLfloat triangle_pos[] = //not part of the snippet -> too long
//generate vbo for the positions:
GLuint pos_vbo;
glGenBuffers(1, &pos_vbo);
glBindBuffer(GL_ARRAY_BUFFER, pos_vbo);
glBufferData(GL_ARRAY_BUFFER, sizeof(triangle_pos), triangle_pos, GL_STATIC_DRAW);
//next, generate the vertex colors:
GLfloat triangle_color[] = //not part of the snippet -> too long
//generate vbo for the colors:
GLuint col_vbo;
glGenBuffers(1, &col_vbo);
glBindBuffer(GL_ARRAY_BUFFER, col_vbo);
glBufferData(GL_ARRAY_BUFFER, sizeof(triangle_color), triangle_color, GL_STATIC_DRAW);
//generate VAO:
GLuint vao;
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
GLint pos_attrib_id = glGetAttribLocation(programID, "line_pos");
glEnableVertexAttribArray(pos_attrib_id);
glBindBuffer(GL_ARRAY_BUFFER, pos_vbo);
glVertexAttribPointer(pos_attrib_id, 3, GL_FLOAT, GL_FALSE, 0, (void*)0);
GLint col_attrib_id = glGetAttribLocation(programID, "color");
glEnableVertexAttribArray(col_attrib_id);
glBindBuffer(GL_ARRAY_BUFFER, col_vbo);
glVertexAttribPointer(col_attrib_id, 4, GL_FLOAT, GL_FALSE, 0, (void*)0);
//function to set the perspective (argument is the model matrix)
setPerspective(glm::mat4(1.0f));
return vao;
}
有了这个代码,但只有立方体被绘制。 此外,如果我注释掉主线中的线条: glBindVertexArray(cube_vao);
和glDrawArrays(GL_TRIANGLES, 0, 12*3);
,则三角形会被绘制出来,但具有立方体的颜色和位置,这让我发疯。
如果有帮助,我使用OSX和着色器版本120。
检查generate *的返回值并查看它是否有效VAO –
另外,检查'glGetAttribLocation'返回的值是否不是'-1'。 – legends2k
@ legends2k @ratchet freak三角形的VAO:0,立方体的VAO:0,glGetAttribLocation的返回值是正值。如果我倒转立方体:0,VAO的三角形:1375791943(可能是-1?)的'drawTriangle()'和'drawCube()':VAO的顺序。 – KO70