顶点未在 opengl 中读取

Question

我有一个问题，当顶点的某些部分没有被opengl读取时，我该怎么办？我的意思是当我运行代码时，它没有遵循我在方格纸上所做的坐标网格，甚至在我删除该顶点后，它仍然显示相同的输出。我想做枫叶

我想通过降低特定顶点的 y 值来使用直线制作某种曲线，但是当我运行代码时，而不是将线制作到我已经设置的坐标，它跳过我设置的那个顶点并转到另一个顶点并创建一条直线。

比方说，我设置顶点 A(-0.44, 0.16) B(-0.46, 0.16) C(-0.52, 0.18) D(-0.54, 0.24)，而不是从 A 到 B 再到 C , 它跳过了 B 和 C 而去了 D.

#include <windows.h>
#include <gl/glut.h>

void display() {

    glClearColor(0.3, 0.1, 0.1, 0.2);
    glClear(GL_COLOR_BUFFER_BIT);

    //glTranslatef(0.5, 0, 0);
    //glScalef(0.5, 0.5, 0);
    //glRotatef(0, 0, 0, 0);

    //Unifolié also known as Maple Leaf
    glBegin(GL_POLYGON);
    glColor3f(1, 0, 0);
    glVertex2f(0.00, 0.00);
    glVertex2f(0.00, 0.90);
    glVertex2f(-0.08, 0.70);
    glVertex2f(-0.12, 0.66);
    glVertex2f(-0.16, 0.66);
    glVertex2f(-0.20, 0.68);
    glVertex2f(-0.24, 0.74);
    glVertex2f(-0.22, 0.64);
    glVertex2f(-0.22, 0.62);
    glVertex2f(-0.24, 0.56);
    glVertex2f(-0.26, 0.54);
    glVertex2f(-0.30, 0.54);
    glVertex2f(-0.34, 0.56);
    glVertex2f(-0.36, 0.60);
    glVertex2f(-0.36, 0.56);
    glVertex2f(-0.38, 0.54);
    glVertex2f(-0.40, 0.54);
    glVertex2f(-0.42, 0.54);
    glVertex2f(-0.56, 0.60);
    glVertex2f(-0.52, 0.54);
    glVertex2f(-0.50, 0.50);
    glVertex2f(-0.48, 0.44);
    glVertex2f(-0.48, 0.42);
    glVertex2f(-0.50, 0.38);
    glVertex2f(-0.54, 0.34);
    glVertex2f(-0.48, 0.32);
    glVertex2f(-0.44, 0.28);
    glVertex2f(-0.42, 0.22);
    glVertex2f(-0.42, 0.20);
    glVertex2f(-0.44, 0.16);
    glVertex2f(-0.46, 0.16); //this 1st
    glVertex2f(-0.52, 0.18);
    glVertex2f(-0.54, 0.24);
    glVertex2f(-0.54, 0.20);
    glVertex2f(-0.56, 0.16);
    glVertex2f(-0.60, 0.14);
    glVertex2f(-0.62, 0.14);
    glVertex2f(-0.70, 0.16);
    glVertex2f(-0.76, 0.20);
    glVertex2f(-0.78, 0.24);
    glVertex2f(-0.76, 0.18);
    glVertex2f(-0.74, 0.14);
    glVertex2f(-0.70, 0.08);
    glVertex2f(-0.68, 0.06);
    glVertex2f(-0.66, 0.02);
    glVertex2f(-0.66, 0.00);
    glVertex2f(-0.68, -0.04);
    glVertex2f(-0.64, -0.02);
    glVertex2f(-0.62, -0.02);
    glVertex2f(-0.56, -0.04);
    glVertex2f(-0.52, -0.08);
    glVertex2f(-0.48, -0.16);
    glVertex2f(-0.48, -0.20);
    glVertex2f(-0.50, -0.26);
    glVertex2f(-0.52, -0.30);
    glVertex2f(-0.58, -0.34);
    glVertex2f(-0.42, -0.32);
    glVertex2f(-0.30, -0.28);
    glVertex2f(-0.18, -0.22);
    glVertex2f(-0.10, -0.20);
    glVertex2f(0.00, -0.22);

    glVertex2f(0.10, -0.20);
    glVertex2f(0.18, -0.22);
    glVertex2f(0.30, -0.28);
    glVertex2f(0.42, -0.32);
    glVertex2f(0.58, -0.34);
    glVertex2f(0.52, -0.30);
    glVertex2f(0.50, -0.26);
    glVertex2f(0.48, -0.20);
    glVertex2f(0.48, -0.16);
    glVertex2f(0.52, -0.08);
    glVertex2f(0.56, -0.04);
    glVertex2f(0.62, -0.02);
    glVertex2f(0.64, -0.02);
    glVertex2f(0.68, -0.04);
    glVertex2f(0.66, 0.00);
    glVertex2f(0.66, 0.02);
    glVertex2f(0.68, 0.06);
    glVertex2f(0.70, 0.08);
    glVertex2f(0.74, 0.14);
    glVertex2f(0.76, 0.18);
    glVertex2f(0.78, 0.24);
    glVertex2f(0.76, 0.20);
    glVertex2f(0.70, 0.16);
    glVertex2f(0.62, 0.14);
    glVertex2f(0.60, 0.14);
    glVertex2f(0.56, 0.16);
    glVertex2f(0.54, 0.20);
    glVertex2f(0.54, 0.24);
    glVertex2f(0.52, 0.18);
    glVertex2f(0.46, 0.16);
    glVertex2f(0.44, 0.16);
    glVertex2f(0.42, 0.20);
    glVertex2f(0.42, 0.22);
    glVertex2f(0.44, 0.28);
    glVertex2f(0.48, 0.32);
    glVertex2f(0.54, 0.34);
    glVertex2f(0.50, 0.38);
    glVertex2f(0.48, 0.42);
    glVertex2f(0.48, 0.44);
    glVertex2f(0.50, 0.50);
    glVertex2f(0.52, 0.54);
    glVertex2f(0.56, 0.60);
    glVertex2f(0.42, 0.54);
    glVertex2f(0.40, 0.54);
    glVertex2f(0.38, 0.54);
    glVertex2f(0.36, 0.56);
    glVertex2f(0.36, 0.60);
    glVertex2f(0.34, 0.56);
    glVertex2f(0.30, 0.54);
    glVertex2f(0.26, 0.54);
    glVertex2f(0.24, 0.56);
    glVertex2f(0.22, 0.62);
    glVertex2f(0.22, 0.64);
    glVertex2f(0.24, 0.74);
    glVertex2f(0.20, 0.68);
    glVertex2f(0.16, 0.66);
    glVertex2f(0.12, 0.66);
    glVertex2f(0.08, 0.70);
    glVertex2f(0.00, 0.90);
    glEnd();


    glFlush();

}


int main(int argc, char* argv[]) {
    glutInit(&argc, argv);
    glutInitWindowSize(1000, 1000);
    glutInitWindowPosition(10, 10);
    glutCreateWindow("Maple Leaf");
    glutDisplayFunc(display);
    glutMainLoop();
    return 0;
}

Answer 1

这是您的多边形：

你的形状不凸，GL_POLYGON规定：

GL_POLYGON

Draws a single, convex polygon. Vertices 1 through N define this polygon.

要栅格化此轮廓，请手动将您的形状分成三角形或其他原始组件，例如三角形扇形或三角形带。这称为镶嵌。 GL_POLYGON虽然看起来很诱人，但只针对凸形。

(original image source)

对于任意多边形，您需要自己细分轮廓。您可以寻找一个库来执行此操作，例如： https://github.com/mapbox/earcut.hpp 好消息是您只需执行一次，并且可以离线执行（而不是 run-time）。一旦你的多边形被镶嵌，你就可以用 GL_TRIANGLES.

绘制它

顶点未在 opengl 中读取

Vertex not read in opengl

c++

opengl