无法在 OpenTK 中获取正确的名称堆栈

Question

我这里指的是LWJGL教程(https://www.youtube.com/watch?v=V9e7A4konHo) for the picking. The source code for this tutorial can be found here (https://docs.google.com/document/d/1MEcdkcCCM-BKmuL2Rg5SR-_RG6cCH7Ek9_hU7xXlW4Y/pub)。

基本上我想在这里做的是使用 OpenTK 将此 Java 代码转换为 C# 代码。在此代码中，有 2 个对象（矩形）被渲染到屏幕上。然后我想在点击对象的时候得到正确的名字栈。但是，当我运行我的代码时，即使我单击其他对象，我也只会得到相同的名称 1。另外，当我点击对象时，屏幕会放大，这不是我想要的。

我不确定我的代码有什么问题。我怀疑错误的部分是 GluPickMatrix 函数。这是我的代码：

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


namespace OpenTkSelectTry
{
    public class Game2D
    {
        GameWindow window;
        private int BUFSIZE = 512;

        public Game2D(GameWindow wd)
        {
            this.window = wd;
            start();
        }

        public void start()
        {
            window.Load += loaded;
            window.Resize += resize;
            window.MouseDown += select;
            window.RenderFrame += renderFrame;      
            window.Run(1.0 / 60.0);
        }

        public void loaded(object o,EventArgs e)
        {
            GL.ClearColor(0.0f,0.0f,0.0f,0.0f);
        }

        public void renderFrame(object o,EventArgs e)
        {
            GL.LoadIdentity();
            GL.Clear(ClearBufferMask.ColorBufferBit | ClearBufferMask.DepthBufferBit);
            
            GL.Begin(BeginMode.Quads);
            GL.Color3(1.0, 1.0, 0.0);
            GL.Vertex3(-5.0,-5.0,-80.0);
            GL.Vertex3(5.0, -5.0, -80.0);
            GL.Vertex3(5.0, 5.0, -80.0);
            GL.Vertex3(-5.0, 5.0, -80.0);
                     
            GL.Color3(1.0, 0.0, 0.0);
            GL.Vertex3(-10.0, -10.0, -80.0);
            GL.Vertex3(0.0, -10.0, -80.0);
            GL.Vertex3(0.0, 0.0, -80.0);
            GL.Vertex3(-10.0, 0.0, -80.0);
            GL.End();
            window.SwapBuffers();
        }

        public void resize(object o,EventArgs e)
        {
            GL.Viewport(0, 0, window.Width, window.Height);
            GL.MatrixMode(MatrixMode.Projection);
            GL.LoadIdentity();
            GL.Ortho(-50.0, 50.0, -50.0, 50.0, -100.0, 100.0);
            GL.MatrixMode(MatrixMode.Modelview);
            GL.Enable(EnableCap.DepthTest);
        }     

        public void select(object o, MouseEventArgs e)
        {
            var buffer = new int[BUFSIZE];
            var viewPort = new int[4];
            int hits;
            GL.GetInteger(GetPName.Viewport, viewPort);
            GL.SelectBuffer(BUFSIZE, buffer);
            GL.RenderMode(RenderingMode.Select);

            GL.InitNames();
            GL.PushName(0);
            GL.MatrixMode(MatrixMode.Projection);
            GL.PushMatrix();
            GL.LoadIdentity();

            GluPickMatrix(e.Mouse.X, viewPort[3] - e.Mouse.Y, 5.0, 5.0, viewPort);  
            GL.Ortho(-50.0, 50.0, -50.0, 50.0, -100.0, 100.0);             
            GL.MatrixMode(MatrixMode.Modelview);
            GL.LoadIdentity();
            GL.LoadName(1);
            GL.Begin(BeginMode.Quads);
            GL.Color3(1.0, 1.0, 0.0);
            GL.Vertex3(-5.0, -5.0, -80.0);
            GL.Vertex3(5.0, -5.0, -80.0);
            GL.Vertex3(5.0, 5.0, -80.0);
            GL.Vertex3(-5.0, 5.0, -80.0);
   
            GL.LoadName(2);
            GL.Color3(1.0, 0.0, 0.0);
            GL.Vertex3(-10.0, -10.0, -80.0);
            GL.Vertex3(0.0, -10.0, -80.0);
            GL.Vertex3(0.0, 0.0, -80.0);
            GL.Vertex3(-10.0, 0.0, -80.0);
            GL.End();    
            GL.PopMatrix();

            GL.Flush();

            hits = GL.RenderMode(RenderingMode.Render);
            Console.WriteLine("hit: {0}", hits);

            if (hits>0)
            {
                int choose = buffer[3];
                int depth = buffer[1];
                for (int i=0;i<hits;i++)
                {
                    if (buffer[i * 4 + 1] < depth)
                    {
                        choose = buffer[i * 4 + 3];
                        depth = buffer[i * 4 + 1];
                    }
                }
                Console.WriteLine("choosen: {0}", choose);
            }     
        }
        private void GluPickMatrix(double x, double y, double deltax, double deltay, int[] viewport)
        {
            if (deltax <= 0 || deltay <= 0)
            {
                return;
            }

            GL.Translate((viewport[2] - 2 * (x - viewport[0])) / deltax, (viewport[3] - 2 * (y - viewport[1])) / deltay, 0);
            GL.Scale(viewport[2] / deltax, viewport[3] / deltay, 1.0);
        }
    }
}

主要功能：

using System;
using OpenTK;

namespace OpenTkSelectTry
{
    class Program
    {
        static void Main(string[] args)
        {
            var window = new GameWindow(500, 500);
            var gm = new Game2D(window);
            Console.WriteLine();
            Console.WriteLine();
            Console.WriteLine("Press enter to finish...");
            Console.ReadLine();
        }
    }
}

这是最初在屏幕上呈现的 2 个对象：

点击对象后，屏幕放大（不是我想要的），名称堆栈不正确（总是1）。

Answer 1

the screen zoom in (not what I want),

这是因为您在 select 方法中更改了矩阵模式。在GL.PopMatrix()之前选择MatrixMode.Projection:

and the name stack is not correct (always 1).

不允许在 GL.Begin/GL.End 序列中调用 GL.LoadName。这会导致无效操作错误 (GL.GetError)。您需要绘制 2 个独立的四边形。

public void select(object o, MouseEventArgs e)
{
    // [...]

    GL.MatrixMode(MatrixMode.Projection);
    GL.PushMatrix();
    GL.LoadIdentity();

    GluPickMatrix(e.Mouse.X, viewPort[3] - e.Mouse.Y, 5.0, 5.0, viewPort);
    GL.Ortho(-50.0, 50.0, -50.0, 50.0, -100.0, 100.0);

    GL.MatrixMode(MatrixMode.Modelview);
    GL.LoadIdentity();

    GL.LoadName(1);
    GL.Begin(BeginMode.Quads);
    GL.Color3(1.0, 1.0, 0.0);
    GL.Vertex3(-5.0, -5.0, -80.0);
    GL.Vertex3(5.0, -5.0, -80.0);
    GL.Vertex3(5.0, 5.0, -80.0);
    GL.Vertex3(-5.0, 5.0, -80.0);
    GL.End();

    GL.LoadName(2);
    GL.Begin(BeginMode.Quads);
    GL.Color3(1.0, 0.0, 0.0);
    GL.Vertex3(-10.0, -10.0, -80.0);
    GL.Vertex3(0.0, -10.0, -80.0);
    GL.Vertex3(0.0, 0.0, -80.0);
    GL.Vertex3(-10.0, 0.0, -80.0);
    GL.End();
  
    GL.MatrixMode(MatrixMode.Projection);
    GL.PopMatrix();
    GL.MatrixMode(MatrixMode.Modelview);

    // [...]
}

原始示例使用 Perspective projection instead of Orthographic projection。使用 Matrix4.CreatePerspectiveFieldOfView 指定透视投影矩阵。使用GL.MultMatrix将当前矩阵乘以投影矩阵：

~~GL.Ortho(-50.0, 50.0, -50.0, 50.0, -100.0, 100.0);~~

Matrix4 perspective = Matrix4.CreatePerspectiveFieldOfView(
    40f * (float)Math.PI / 180f, 500f / 500f, 0.001f, 400f);
GL.MultMatrix(ref perspective);

无法在 OpenTK 中获取正确的名称堆栈

Cannot get the correct name stack in OpenTK

c#

opengl

opentk