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OpenTK. Drawing points by mouse click (port from WebGL)

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#1 8Observer8   Members   

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Posted 04 March 2017 - 11:41 PM

Hello,

I try to port this example from WebGL: ch02/ClickedPoints in OpenTK. This example draws the points in position of mouse click.

I draw one point in my example. In beginning the point is drawn in (0, 0.5). Drawing loop is 30 frames per second. When I click on the window area the point must to be redrawn in (0, 0) position.

You can run and test my problem in VS2012 - VS2015: DrawPointsByClick_Problem.zip

VertexShader.glsl

#version 330

in vec4 a_Position;

void main()
{
    gl_Position = a_Position;
    gl_PointSize = 10.0;
}

FragmentShader.glsl

#version 330

out vec4 fragColor;

void main()
{
    fragColor = vec4(0.0, 1.0, 1.0, 1.0);
}

Program.cs

namespace DrawPointsByClick
{
    class Program
    {
        static void Main(string[] args)
        {
            using (var mainWindow = new MainWindow())
            {
                mainWindow.Run(30);
            }
        }
    }
}

MainWindow.cs

using System;
using System.Drawing;
using OpenTK;
using OpenTK.Graphics.OpenGL;
using Utils;
using OpenTK.Input;

namespace DrawPointsByClick
{
    class MainWindow : GameWindow
    {
        private int program;
        private bool canDraw = false;
        private int a_Position;

        protected override void OnLoad(EventArgs e)
        {
            base.OnLoad(e);

            // Load shaders from files
            string vShaderSource = null;
            string fShaderSource = null;
            ShaderLoader.LoadShader("./Shaders/VertexShader.glsl", out vShaderSource);
            ShaderLoader.LoadShader("./Shaders/FragmentShader.glsl", out fShaderSource);
            if (vShaderSource == null || fShaderSource == null)
            {
                Logger.Append("Failed to load shaders from files");
                return;
            }

            // Initialize the shaders
            if (!ShaderLoader.InitShaders(vShaderSource, fShaderSource, out program))
            {
                Logger.Append("Failed to initialize the shaders");
                return;
            }

            // Get the storage location of a_Position
            a_Position = GL.GetAttribLocation(program, "a_Position");
            if (a_Position < 0)
            {
                Logger.Append("Failed to get the storage location of a_Position");
                return;
            }

            // Pass coordinates of point to a_Position
            GL.VertexAttrib2(a_Position, 0f, 0.5f);

            // Enable Point Size
            GL.Enable(EnableCap.ProgramPointSize);

            // Specify the color for clearing the canvas
            GL.ClearColor(Color.OliveDrab);

            canDraw = true;
        }

        protected override void OnRenderFrame(FrameEventArgs e)
        {
            GL.Viewport(0, 0, Width, Height);
            base.OnRenderFrame(e);

            // Clear the canvas with current color
            GL.Clear(ClearBufferMask.ColorBufferBit);

            if (canDraw)
            {
                // Draw the points
                GL.DrawArrays(PrimitiveType.Points, 0, 1);
            }

            GL.Flush();
            SwapBuffers();
        }

        protected override void OnMouseDown(MouseButtonEventArgs e)
        {
            base.OnMouseDown(e);

            Console.WriteLine("OnMouseDown");

            // Pass coordinates of point to a_Position
            GL.VertexAttrib2(a_Position, 0f, 0f);
        }
    }
}

Utils.cs

using System;
using OpenTK.Graphics.OpenGL;
using System.IO;

namespace Utils
{
    public class ShaderLoader
    {
        ///<summary>
        ///Create a program object and make current
        ///</summary>
        ///<param name="vShader">a vertex shader program</param>
        ///<param name="fShader">a fragment shader program</param>
        ///<param name="program">created program</param>
        ///<returns>
        ///return true, if the program object was created and successfully made current
        ///</returns>
        public static bool InitShaders(string vShaderSource, string fShaderSource, out int program)
        {
            program = CreateProgram(vShaderSource, fShaderSource);
            if (program == 0)
            {
                Logger.Append("Failed to create program");
                return false;
            }

            GL.UseProgram(program);

            return true;
        }

        ///<summary>
        ///Load a shader from a file
        ///</summary>
        ///<param name="errorOutputFileName">a file name for error messages</param>
        ///<param name="fileName">a file name to a shader</param>
        ///<param name="shaderSource">a shader source string</param>
        public static void LoadShader(string shaderFileName, out string shaderSource)
        {
            if (File.Exists(Logger.logFileName))
            {
                // Clear File
                File.WriteAllText(Logger.logFileName, "");
            }

            shaderSource = null;

            using (StreamReader sr = new StreamReader(shaderFileName))
            {
                shaderSource = sr.ReadToEnd();
            }
        }

        private static int CreateProgram(string vShader, string fShader)
        {
            // Create shader object
            int vertexShader = LoadShader(ShaderType.VertexShader, vShader);
            int fragmentShader = LoadShader(ShaderType.FragmentShader, fShader);
            if (vertexShader == 0 || fragmentShader == 0)
            {
                return 0;
            }

            // Create a program object
            int program = GL.CreateProgram();
            if (program == 0)
            {
                return 0;
            }

            // Attach the shader objects
            GL.AttachShader(program, vertexShader);
            GL.AttachShader(program, fragmentShader);

            // Link the program object
            GL.LinkProgram(program);

            // Check the result of linking
            int status;
            GL.GetProgram(program, GetProgramParameterName.LinkStatus, out status);
            if (status == 0)
            {
                string errorString = string.Format("Failed to link program: {0}" + Environment.NewLine, GL.GetProgramInfoLog(program));
                Logger.Append(errorString);
                GL.DeleteProgram(program);
                GL.DeleteShader(vertexShader);
                GL.DeleteShader(fragmentShader);
                return 0;
            }

            return program;
        }

        private static int LoadShader(ShaderType shaderType, string shaderSource)
        {
            // Create shader object
            int shader = GL.CreateShader(shaderType);
            if (shader == 0)
            {
                Logger.Append("Unable to create shader");
                return 0;
            }

            // Set the shader program
            GL.ShaderSource(shader, shaderSource);

            // Compile the shader
            GL.CompileShader(shader);

            // Check the result of compilation
            int status;
            GL.GetShader(shader, ShaderParameter.CompileStatus, out status);
            if (status == 0)
            {
                string errorString = string.Format("Failed to compile {0} shader: {1}", shaderType.ToString(), GL.GetShaderInfoLog(shader));
                Logger.Append(errorString);
                GL.DeleteShader(shader);
                return 0;
            }

            return shader;
        }
    }

    public class Logger
    {
        public static string logFileName = "info.txt";

        /// <summary>
        /// Write a message to a log file
        /// </summary>
        /// <param name="message">a message that will append to a log file</param>
        public static void Append(string message)
        {
            File.AppendAllText(logFileName, message + Environment.NewLine);
        }
    }
}

Attached Files


Edited by 8Observer8, 05 March 2017 - 02:45 AM.

Sorry if I make mistakes. My English is not good for a while yet.


#2 8Observer8   Members   

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Posted 07 March 2017 - 12:46 AM

The solution:
 
1. Open to: C:\Program Files (x86)\Microsoft Visual Studio 12.0\Common7\IDE
2. Right click on devenv.exe.
3. Hover to the "Run with graphics processor..."
4. Select "High-end NVidia processor".
 

Sorry if I make mistakes. My English is not good for a while yet.


#3 8Observer8   Members   

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Posted 07 March 2017 - 02:02 AM

This code draws the point in mouse click position:

protected override void OnMouseDown(MouseButtonEventArgs e)
{
    base.OnMouseDown(e);

    if (e.Button == MouseButton.Left)
    {
        float x = (e.X - Width / 2f) / (Width / 2f);
        float y = -(e.Y - Height / 2f) / (Height / 2f);
        // Pass coordinates of point to a_Position
        GL.VertexAttrib2(a_Position, x, y);

        Console.WriteLine(x + " " + y);
    }
}


Edited by 8Observer8, 07 March 2017 - 02:04 AM.

Sorry if I make mistakes. My English is not good for a while yet.


#4 8Observer8   Members   

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Posted 07 March 2017 - 06:07 AM

Maybe my port of program "ClickedPoints" will be useful for someone.

These programs are equivalent:

Screenshot:

 DrawPointsByClick.png


Sorry if I make mistakes. My English is not good for a while yet.





Old topic!

Guest, the last post of this topic is over 60 days old and at this point you may not reply in this topic. If you wish to continue this conversation start a new topic.