英文:
C++ OpenGL I can't see a cube on the screen
问题
抱歉，我无法提供代码翻译，以下是你的代码的描述：
你在屏幕上看不到一个立方体。你使用glTranslatef定位了它，然后用LoadIdentity使其停在某个位置。你想通过改变矩阵模式来得到一个摄像头，但是立方体并没有出现。
你的代码包括一个立方体的顶点和颜色数组，以及用于绘制立方体的函数drawCube()。在主函数main()中，你初始化了窗口和OpenGL环境，设置了键盘回调函数，启用了深度测试，并在一个循环中进行绘制操作。
在循环中，你设置了视口，清除颜色和深度缓冲区，设置了投影矩阵，并使用gluLookAt()设置了视图矩阵。然后通过glTranslatef()将立方体移动到指定位置，并调用drawCube()函数进行绘制。最后交换缓冲区并处理事件。
你怀疑无法绘制立方体，但检查代码后发现绘制立方体的部分没有问题。可能的原因需要进一步检查OpenGL的状态设置、摄像机位置、视角设置或者渲染管线的配置。
英文:
I can't see a cube on the screen.I located it with glTranslatef. I got it to stop somewhere with LoadIdentity. I wanted to get a camera by changing the Matrix Modes, but the cube does not appear.
Code:
#include <Windows.h>
#include <gl/GL.h>
#include <gl/GLU.h>
#include <GLFW/glfw3.h>
#include <cstdio>
int width = 1280;
int height = 720;
GLfloat vertices[] = {
-1, -1, -1, -1, -1, 1, -1, 1, 1, -1, 1, -1,
1, -1, -1, 1, -1, 1, 1, 1, 1, 1, 1, -1,
-1, -1, -1, -1, -1, 1, 1, -1, 1, 1, -1, -1,
-1, 1, -1, -1, 1, 1, 1, 1, 1, 1, 1, -1,
-1, -1, -1, -1, 1, -1, 1, 1, -1, 1, -1, -1,
-1, -1, 1, -1, 1, 1, 1, 1, 1, 1, -1, 1
};
GLfloat colors[] =
{
0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0,
0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0,
0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0,
0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0,
0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0,
0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0
};
void keyboard(GLFWwindow* window, int key, int scancode, int action, int mods) {
if (action == GLFW_PRESS)
if (key == GLFW_KEY_ESCAPE)
glfwSetWindowShouldClose(window, GL_TRUE);
}
void drawCube() {
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_COLOR_ARRAY);
glVertexPointer(3, GL_FLOAT, 0, vertices);
glColorPointer(3, GL_FLOAT, 0, colors);
glDrawArrays(GL_QUADS, 0, 24);
glDisableClientState(GL_VERTEX_ARRAY);
glDisableClientState(GL_COLOR_ARRAY);
}
int main(void)
{
GLFWwindow* window;
/* Initialize the library */
if (!glfwInit())
return -1;
/* Create a windowed mode window and its OpenGL context */
window = glfwCreateWindow(width, height, "C++ OpenGL Test Area", NULL, NULL);
if (!window)
{
glfwTerminate();
return -1;
}
/* Make the window's context current */
glfwMakeContextCurrent(window);
glfwSetKeyCallback(window, keyboard);
glEnable(GL_DEPTH_TEST);
/* Loop until the user closes the window */
while (!glfwWindowShouldClose(window))
{
glViewport(0, 0, width, height);
/* Render here */
glClearColor(0.0, 192/256, 1, 1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluLookAt(1, 1, 1, 0, 0, 0, 0, 1, 0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glTranslatef(0, 0, 5);
drawCube();
glFlush();
/* Swap front and back buffers */
glfwSwapBuffers(window);
/* Poll for and process events */
glfwPollEvents();
}
glfwTerminate();
return 0;
}
I thought it was because I couldn't draw the cube. I checked the codes again, but there is no problem drawing the cube.
答案1
得分: 1
立方体不在视图体积内。如果你没有指定投影矩阵，视图体积将是围绕相机位置对齐在视线上的一个唯一的立方体。不在视图体积内的任何几何图形都会被裁剪掉。你必须设置一个投影矩阵。投影矩阵定义了在场景中投射到视口上的体积。可以使用 glOrtho 设置正交投影矩阵。可以使用 glFrustum 或 gluPerspective 设置透视投影矩阵。透视投影矩阵定义了一个视景体。例如：
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
float aspect = (float)width / (float)height;
gluPerspective(90.0, aspect, 0.1, 10.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(4, 4, 4, 0, 0, 0, 0, 1, 0);
drawCube();
英文:
The cube is not in the viewing volume. If you do not specify a projection matrix, the viewing volume is a unique cube around the camera position, aligned along the line of sight. Any geometry that is not in the viewing volume is clipped. You must set up a projection matrix. The projection matrix defines the volume in the scene that is projected onto the viewport. An orthographic projection matrix can be set with glOrtho. A perspective projection matrix can be set with glFrustum or gluPerspective. The perspective projection matrix defines a Viewing frustum. e.g.:
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
float aspect = (float)width / (float)height;
gluPerspective(90.0, aspect, 0.1, 10.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(4, 4, 4, 0, 0, 0, 0, 1, 0);
drawCube();
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