OpenGL
[OpenGL] Boundary and nonboundary edge flags 다각형의 경계선 설정하기
J-sean
2019. 12. 20. 11:09
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Each vertex of a polygon, separate triangle, or separate quadrilateral specified between a glBegin/glEnd pair is marked as the start of either a boundary or nonboundary edge. If the current edge flag is TRUE when the vertex is specified, the vertex is marked as the start of a boundary edge. If the current edge flag is FALSE, the vertex is marked as the start of a nonboundary edge.
OpenGL에서 선을 그릴때 다각형의 경계선인지 숨겨야할 내부선인지 결정 할 수 있다.
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#include <gl/glut.h>
void DoDisplay();
int main(int argc, char** argv)
{
glutInit(&argc, argv);
glutCreateWindow("OpenGL");
glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
glutDisplayFunc(DoDisplay);
glutMainLoop();
return 0;
}
void DoDisplay()
{
glClear(GL_COLOR_BUFFER_BIT);
glPushMatrix();
glTranslatef(-0.5f, 0.0f, 0.0f);
// 첫 번째 선 Nonboundary 지정
glBegin(GL_TRIANGLES);
glEdgeFlag(GL_FALSE); // 경계선 적용 여부를 선택할 선의 시작점 선언 전에 glEdgeFlag()를 호출.
// Flags edges as either boundary or nonboundary.
glVertex2f(0.0f, 0.2f);
glEdgeFlag(GL_TRUE);
glVertex2f(-0.2f, -0.2f);
glVertex2f(0.2f, -0.2f);
glEnd();
glTranslatef(0.5f, 0.0f, 0.0f);
// 두 번째 선 Nonboundary 지정
glBegin(GL_TRIANGLES);
glVertex2f(0.0f, 0.2f);
glEdgeFlag(GL_FALSE);
glVertex2f(-0.2f, -0.2f);
glEdgeFlag(GL_TRUE);
glVertex2f(0.2f, -0.2f);
glEnd();
glTranslatef(0.5f, 0.0f, 0.0f);
// 세 번째 선 Nonboundary 지정
glBegin(GL_TRIANGLES);
glVertex2f(0.0f, 0.2f);
glVertex2f(-0.2f, -0.2f);
glEdgeFlag(GL_FALSE);
glVertex2f(0.2f, -0.2f);
glEdgeFlag(GL_TRUE);
glEnd();
glPopMatrix();
glFlush();
}
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Run the program.
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