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);
}
}
}
