how to fill ellipse in openGL?

Question

and in openGL the width of the window is1.0f?

I want to use openGL to fill ellipse how to do it?

Answer 1

You can see https://www.codeproject.com/Articles/67357/OpenGL-Oval

or from ChatGPT :

void DrawEllipse(float xCenter, float yCenter, float xRadius, float yRadius) {
	int numSegments = 100;  // The number of segments for the circle approximation
	float angleStep = (2.0f * 3.14159f) / numSegments;

	// Draw filled ellipse
	glBegin(GL_TRIANGLE_FAN);
	glVertex2f(xCenter, yCenter);  // Center of the ellipse
	for (int i = 0; i <= numSegments; i++) {
		float angle = i * angleStep;
		float x = xCenter + cosf(angle) * xRadius;
		float y = yCenter + sinf(angle) * yRadius;
		glVertex2f(x, y);
	}
	glEnd();

	// Draw ellipse outline
	glBegin(GL_LINE_LOOP);
	for (int i = 0; i <= numSegments; i++) {
		float angle = i * angleStep;
		float x = xCenter + cosf(angle) * xRadius;
		float y = yCenter + sinf(angle) * yRadius;
		glVertex2f(x, y);
	}
	glEnd();
}

By testing in Nehe's Lesson 5 tutorial:

gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);

replaced by

glOrtho(0.0f, width, height, 0.0f, -1.0f, 1.0f);

in DrawGLScene :

glColor3f(1.0f, 0.0f, 0.0f);
DrawEllipse(200.0f, 200.0f, 100.0f, 50.0f); 

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