Question

I am trying to draw an explosion. By draw, I mean using the e.graphics function as opposed to using a Picturebox(like I did last time).

Now my question is, that how exactly would I go about doing this? In my mind, I’m thinking of using the e.graphics.fillrectangle(x,y,w,h) and well…alterating the location and the colour to create a composite image which resembles an explosion. However, the process seems a bit hit and miss, since I have to experiment to try and do this – is there a way to do this more effectively?

Answer 1

You might find the FillPolygonPoint method to be more use.

Imagine all the points of your explosion like this:

Then the code to draw it looks something along the lines of:

Public Sub FillPolygonPoint(ByVal e As PaintEventArgs)

  ' Create solid brush. 
  Dim blueBrush As New SolidBrush(Color.Blue)

  ' Create points that define polygon. 
  Dim point1 As New Point(50, 50)
  Dim point2 As New Point(100, 25)
  Dim point3 As New Point(200, 5)
  Dim point4 As New Point(250, 50)
  Dim point5 As New Point(300, 100)
  Dim point6 As New Point(350, 200)
  Dim point7 As New Point(250, 250)
  Dim curvePoints As Point() = {point1, point2, point3, point4, _
    point5, point6, point7}

  ' Draw polygon to screen.
  e.Graphics.FillPolygon(blueBrush, curvePoints)
End Sub

As outlined in the documentation provided by Microsoft.

An algorithm (in C#) to create the points of a star dynamically might look like this:

using System;
using System.Drawing;
using System.Collections.Generic;

namespace Explosion
{
    class Program
    {
        static void Main(string[] args)
        {
            foreach (Point point in CreatePointsForStarShape(15, 200, 100))
            {
                Console.WriteLine(point);
            }
            Console.ReadLine();
        }

        public static IEnumerable<Point> CreatePointsForStarShape
                  (int numberOfPoints, int maxRadius, int minRadius)
        {
            List<Point> points = new List<Point>(numberOfPoints);

            for (
                 double angle = 0.0;
                 angle < 2* Math.PI;
                 angle += 2 * Math.PI / numberOfPoints
            )
            {
                // add outer point
                points.Add(CalculatePoint(angle, maxRadius));

                // add inner point
                points.Add(CalculatePoint
                    (angle + (Math.PI / numberOfPoints), minRadius));
            }

            return points;
        }

        public static Point CalculatePoint(double angle, int radius)
        {
            return new Point(
               (int)(Math.Sin(angle) * radius),
               (int)(Math.Cos(angle) * radius)
            );
        }
    }
}

Here’s the output…

{X=0,Y=200}
{X=20,Y=97}
{X=81,Y=182}
{X=58,Y=80}
{X=148,Y=133}
{X=86,Y=50}
{X=190,Y=61}
{X=99,Y=10}
{X=198,Y=-20}
{X=95,Y=-30}
{X=173,Y=-99}
{X=74,Y=-66}
{X=117,Y=-161}
{X=40,Y=-91}
{X=41,Y=-195}
{X=0,Y=-100}
{X=-41,Y=-195}
{X=-40,Y=-91}
{X=-117,Y=-161}
{X=-74,Y=-66}
{X=-173,Y=-99}
{X=-95,Y=-30}
{X=-198,Y=-20}
{X=-99,Y=10}
{X=-190,Y=61}
{X=-86,Y=50}
{X=-148,Y=133}
{X=-58,Y=80}
{X=-81,Y=182}
{X=-20,Y=97}
{X=0,Y=200}
{X=20,Y=97}

You will have to translate this to Visual Basic and add some randomization to give it an explosive look. You could transpose (move) and scale the points through matrix multiplication.