OpenGL中基本三维物体的绘制

本文介绍一下OpenGL下绘制三维物体的基本方法。编译环境:OpenTK, c#。

 以下是OpenGL的基本绘图函数:

Geometric Primitive Types in OpenTK.OpenGL

 

1. 绘制正方体

View Code
//draw a cube: solid
        void DrawCube(Color color, Vector3d refMarker, Vector3d size)
        {
            List<Vector3d> points = new List<Vector3d>(); //points
            
            //back points (anti-clockwise)
            points.Add(refMarker);
            points.Add(new Vector3d(points[0].X + size.X, points[0].Y, points[0].Z));
            points.Add(new Vector3d(points[0].X + size.X, points[0].Y + size.Y, points[0].Z));
            points.Add(new Vector3d(points[0].X, points[0].Y + size.Y, points[0].Z));

            //front points (anti-clockwise)
            points.Add(new Vector3d(points[0].X, points[0].Y, points[0].Z + size.Z));
            points.Add(new Vector3d(points[1].X, points[1].Y, points[1].Z + size.Z));
            points.Add(new Vector3d(points[2].X, points[2].Y, points[2].Z + size.Z));
            points.Add(new Vector3d(points[3].X, points[3].Y, points[3].Z + size.Z));

            //sequency
            int[] seqs = { 
                             0, 1, 2, 3, //back side
                             4, 5, 6, 7, //front side
                             0, 4, 7, 3, //left side
                             1, 5, 6, 2, //right side
                             0, 4, 5, 1, //bottom side
                             3, 7, 6, 2  //tope side
                         };


            GL.ShadeModel(ShadingModel.Flat);
            GL.Color3(color);
            GL.Begin(BeginMode.Quads);
            foreach (int seq in seqs)
            {
                GL.Vertex3(points[seq]);
            }
            GL.End();

        }

 

2. 圆筒

View Code
void DrawCylinder(Color color, Vector3d refMarker, double radius, double length, int segments = 20, int sides = 20)
        {
            GL.Color3(color);
            GL.ShadeModel(ShadingModel.Flat);

            double thetaSegments = 2 * Math.PI / segments;
            double thetaSides = 2 * Math.PI / sides;

            //bottom
            
            GL.Begin(BeginMode.Polygon);
            for (double i = 0; i < segments; i++)
            {
                Vector3d point = new Vector3d();
                point.X = refMarker.X + radius * Math.Cos(thetaSegments * i);
                point.Y = refMarker.Y + radius * Math.Sin(thetaSegments * i);
                point.Z = refMarker.Z;
                GL.Vertex3(point);
            }
            GL.End();

            //top
            
            GL.Begin(BeginMode.Polygon);
            for (double i = 0; i < segments; i++)
            {
                Vector3d point = new Vector3d();
                point.X = refMarker.X + radius * Math.Cos(thetaSegments * i);
                point.Y = refMarker.Y + radius * Math.Sin(thetaSegments * i);
                point.Z = refMarker.Z + length;
                GL.Vertex3(point);
            }
            GL.End();

            //side
            
            GL.Begin(BeginMode.QuadStrip);
            for (double i = 0; i <= sides; i++)
            {
                Vector3d point1 = new Vector3d();
                point1.X = refMarker.X + radius * Math.Cos(thetaSides * i);
                point1.Y = refMarker.Y + radius * Math.Sin(thetaSides * i);
                point1.Z = refMarker.Z;
                GL.Vertex3(point1);

                Vector3d point2 = new Vector3d();
                point2.X = refMarker.X + radius * Math.Cos(thetaSides * i);
                point2.Y = refMarker.Y + radius * Math.Sin(thetaSides * i);
                point2.Z = refMarker.Z + length;
                GL.Vertex3(point2);
            }
            GL.End();
   
        }

 

3. 球型

View Code
//draw a sphere: solid
        void DrawSphere(Color color, Vector3d refMarker, double radius)
        {
            int longitudes = 20;
            int latitudes = 20;
            GL.Color3(color);
            GL.ShadeModel(ShadingModel.Smooth);

            for (double i = 0; i < latitudes; i++)
            {
                double lat0 = -Math.PI / 2 + Math.PI/latitudes * i ;
                double z0 = Math.Sin(lat0) * radius;
                double r0 = Math.Abs(Math.Cos(lat0) * radius);

                double lat1 = -Math.PI / 2 + Math.PI / latitudes * (i + 1);
                double z1 = Math.Sin(lat1) * radius;
                double r1 = Math.Abs(Math.Cos(lat1) * radius);
                
                GL.Begin(BeginMode.QuadStrip);
                for (double j = 0; j < longitudes; j++)
                {
                    double lng = 2 * Math.PI * j / longitudes;
                    double x = Math.Cos(lng);
                    double y = Math.Sin(lng);

                    Vector3d pt0 = new Vector3d(x * r0 + refMarker.X, y * r0 + refMarker.Y, z0 + refMarker.Z);
                    GL.Normal3(pt0);
                    GL.Vertex3(pt0);

                    Vector3d pt1 = new Vector3d(x * r1 + refMarker.X, y * r1 + refMarker.Y, z1 + refMarker.Z);
                    GL.Normal3(pt1);
                    GL.Vertex3(pt1);
                }
                GL.End();
            }
        }

 

4. Marker

View Code
//Draw a marker
void DrawMarker(Color color, Vector3d origin, double size=1)
        {
            DrawMarkerAxis(color, origin, new Vector3d(size, 0, 0));  //x
            DrawMarkerAxis(color, origin, new Vector3d(0, size, 0));  //y
            DrawMarkerAxis(color, origin, new Vector3d(0, 0, size));  //z
        }

        void DrawMarkerAxis(Color color, Vector3d origin, Vector3d size)
        {
            double len1 = 0.1;
            double len2 = 0.05;
            List<Vector3d> points = new List<Vector3d>();
            points.Add(origin);
            points.Add(new Vector3d(origin.X + size.X, origin.Y + size.Y, origin.Z+size.Z));
            points.Add(new Vector3d(points[1].X * (1 - len1), points[1].Y * (1 - len1), points[1].Z * (1 - len1)));

            if (size.X != 0)
            {
                points.Add(new Vector3d(points[2].X, points[2].Y - len2, points[2].Z));
                points.Add(new Vector3d(points[2].X, points[2].Y + len2, points[2].Z));
                points.Add(new Vector3d(points[2].X, points[2].Y, points[2].Z - len2));
                points.Add(new Vector3d(points[2].X, points[2].Y, points[2].Z + len2));
            }
            else if (size.Y != 0)
            {
                points.Add(new Vector3d(points[2].X - len2, points[2].Y, points[2].Z));
                points.Add(new Vector3d(points[2].X + len2, points[2].Y, points[2].Z));
                points.Add(new Vector3d(points[2].X, points[2].Y, points[2].Z - len2));
                points.Add(new Vector3d(points[2].X, points[2].Y, points[2].Z + len2));
            }
            else
            {
                points.Add(new Vector3d(points[2].X - len2, points[2].Y, points[2].Z));
                points.Add(new Vector3d(points[2].X + len2, points[2].Y, points[2].Z));
                points.Add(new Vector3d(points[2].X, points[2].Y - len2, points[2].Z));
                points.Add(new Vector3d(points[2].X, points[2].Y + len2, points[2].Z));
            }

            GL.Color3(color);
            GL.Begin(BeginMode.Lines);
            GL.Vertex3(points[0]);
            GL.Vertex3(points[1]);
            GL.End();

            GL.Begin(BeginMode.LineLoop);
            GL.Vertex3(points[1]);
            GL.Vertex3(points[3]);
            GL.Vertex3(points[4]);
            GL.End();
            GL.Begin(BeginMode.LineLoop);
            GL.Vertex3(points[1]);
            GL.Vertex3(points[5]);
            GL.Vertex3(points[6]);
            GL.End();

        }

 

posted @ 2012-12-15 20:48  马语者  阅读(4785)  评论(2编辑  收藏  举报