OpenTK---空间中单条线段的绘制

2023-11-11 14:12:46

阅读这篇以前，推荐阅读本专栏之前的内容，之前做过的解释这里不再赘述，专栏目录链接。这里直接上代码并展示最终的效果。
代码如下：

创建主程序中的类

using OpenTK.Mathematics;
using OpenTK.Windowing.Desktop;

namespace OpenTK_SelfMadeBasis
{
    class Program
    {
        static void Main(string[] args)
        {
            NativeWindowSettings nativeWindowSettings = new NativeWindowSettings()
            {
                Size = new Vector2i(800, 600),
                Title = "Draw Single Line",
            };
            using (Window window = new Window(GameWindowSettings.Default, nativeWindowSettings))
            {
                window.Run();
            }
        }
    }
}

构建主程序中调用的GUI窗口界面的类

using OpenTK_SelfMadeBasis.Common;
using OpenTK.Graphics.OpenGL4;
using OpenTK.Windowing.Common;
using OpenTK.Windowing.GraphicsLibraryFramework;
using OpenTK.Windowing.Desktop;

namespace OpenTK_SelfMadeBasis
{
    public class Window : GameWindow
    {
        // 设定线段的两个端点坐标
        private readonly float[] _vertices =
        {
            -0.5f, -0.5f, 0.0f, // 左边端点
             0.5f, -0.5f, 0.0f, // 右边端点
        };

        private int _vertexBufferObject;

        private int _vertexArrayObject;

        private Shader _shader;

        public Window(GameWindowSettings gameWindowSettings, NativeWindowSettings nativeWindowSettings)
            : base(gameWindowSettings, nativeWindowSettings)
        {
        }

        protected override void onl oad()
        {
            GL.ClearColor(0.2f, 0.3f, 0.3f, 1.0f);
            _vertexBufferObject = GL.GenBuffer();

            GL.BindBuffer(BufferTarget.ArrayBuffer, _vertexBufferObject);

            GL.BufferData(BufferTarget.ArrayBuffer, _vertices.Length * sizeof(float), _vertices, BufferUsageHint.StaticDraw);

            _vertexArrayObject = GL.GenVertexArray();
            GL.BindVertexArray(_vertexArrayObject);

            GL.VertexAttribPointer(0, 3, VertexAttribPointerType.Float, false, 3 * sizeof(float), 0);

            GL.EnableVertexAttribArray(0);

            _shader = new Shader("Shaders/shader.vert", "Shaders/shader.frag"); 

            _shader.Use();

            base.OnLoad();
        }

        protected override void OnRenderFrame(FrameEventArgs e)
        {
            GL.Clear(ClearBufferMask.ColorBufferBit);

            _shader.Use();

            GL.BindVertexArray(_vertexArrayObject);
            // 因为我们要画线，所以这里的PrimitiveType要使用Lines类型
            GL.DrawArrays(PrimitiveType.Lines, 0, 2);
         
            SwapBuffers();

            base.OnRenderFrame(e);
        }

        protected override void OnUpdateFrame(FrameEventArgs e)
        {
            var input = KeyboardState;

            if (input.IsKeyDown(Keys.Escape))
            {
                Close();
            }

            base.OnUpdateFrame(e);
        }

        protected override void OnResize(ResizeEventArgs e)
        {
            GL.Viewport(0, 0, Size.X, Size.Y);
            base.OnResize(e);
        }

        protected override void OnUnload()
        {
            GL.BindBuffer(BufferTarget.ArrayBuffer, 0);
            GL.BindVertexArray(0);
            GL.UseProgram(0);

            // Delete all the resources.
            GL.DeleteBuffer(_vertexBufferObject);
            GL.DeleteVertexArray(_vertexArrayObject);

            GL.DeleteProgram(_shader.Handle);
            base.OnUnload();
        }
    }
}

在之前的示例中我们并未详细介绍过GL.DrawArrays(PrimitiveType.Lines, 0, 2)函数的参数，这里做一下补充。

GL.DrawArrays()函数调用方法：

DrawArrays(PrimitiveType mode, int first, int count);

PrimitiveType mode：我们需要设置基础的绘图类型，该参数所有可选的类型如下：

PrimitiveType可用参数	对应数字
Points	0
Lines	1
LineLoop	2
LineStrip	3
Triangles	4
TriangleStrip	5
TriangleFan	6
Quads	7
QuadsExt	7
LinesAdjacency	10
LinesAdjacencyArb	10
LinesAdjacencyExt	10
LineStripAdjacency	11
LineStripAdjacencyArb	11
LineStripAdjacencyExt	11
TrianglesAdjacency	12
TrianglesAdjacencyArb	12
TrianglesAdjacencyExt	12
TriangleStripAdjacency	13
TriangleStripAdjacencyArb	13
TriangleStripAdjacencyExt	13
Patches	14
PatchesExt	14

着色器类

using System;
using System.IO;
using System.Text;
using System.Collections.Generic;
using OpenTK.Graphics.OpenGL4;
using OpenTK.Mathematics;


// 注意这里的K是大写的
// 一定要注意这里改变了namespace的名字并且还要在project->properties中改变namespace的名字才行，否则无效
namespace OpenTK_SelfMadeBasis.Common
{
    public class Shader
    {
        public readonly int Handle;

        private readonly Dictionary<string, int> _uniformLocations;

        public Shader(string vertPath, string fragPath)
        {
            var shaderSource = File.ReadAllText(vertPath);

            var vertexShader = GL.CreateShader(ShaderType.VertexShader);

            GL.ShaderSource(vertexShader, shaderSource);

            CompileShader(vertexShader);

            shaderSource = File.ReadAllText(fragPath);
            var fragmentShader = GL.CreateShader(ShaderType.FragmentShader);
            GL.ShaderSource(fragmentShader, shaderSource);
            CompileShader(fragmentShader);

            Handle = GL.CreateProgram();

            GL.AttachShader(Handle, vertexShader);
            GL.AttachShader(Handle, fragmentShader);

            LinkProgram(Handle);

            GL.DetachShader(Handle, vertexShader);
            GL.DetachShader(Handle, fragmentShader);
            GL.DeleteShader(fragmentShader);
            GL.DeleteShader(vertexShader);
            
            GL.GetProgram(Handle, GetProgramParameterName.ActiveUniforms, out var numberOfUniforms);

            _uniformLocations = new Dictionary<string, int>();

            for (var i = 0; i < numberOfUniforms; i++)
            {
                var key = GL.GetActiveUniform(Handle, i, out _, out _);

                var location = GL.GetUniformLocation(Handle, key);

                _uniformLocations.Add(key, location);
            }
        }

        private static void CompileShader(int shader)
        {
            GL.CompileShader(shader);

            GL.GetShader(shader, ShaderParameter.CompileStatus, out var code);
            if (code != (int)All.True)
            {
                var infoLog = GL.GetShaderInfoLog(shader);
                throw new Exception($"Error occurred whilst compiling Shader({shader}).\n\n{infoLog}");
            }
        }

        private static void LinkProgram(int program)
        {
            GL.LinkProgram(program);

            GL.GetProgram(program, GetProgramParameterName.LinkStatus, out var code);
            if (code != (int)All.True)
            {
                throw new Exception($"Error occurred whilst linking Program({program})");
            }
        }

        public void Use()
        {
            GL.UseProgram(Handle);
        }

        public int GetAttribLocation(string attribName)
        {
            return GL.GetAttribLocation(Handle, attribName);
        }
        
        public void SetInt(string name, int data)
        {
            GL.UseProgram(Handle);
            GL.Uniform1(_uniformLocations[name], data);
        }

        public void SetFloat(string name, float data)
        {
            GL.UseProgram(Handle);
            GL.Uniform1(_uniformLocations[name], data);
        }

        public void SetMatrix4(string name, Matrix4 data)
        {
            GL.UseProgram(Handle);
            GL.UniformMatrix4(_uniformLocations[name], true, ref data);
        }

        public void SetVector3(string name, Vector3 data)
        {
            GL.UseProgram(Handle);
            GL.Uniform3(_uniformLocations[name], data);
        }
    }
}

端点着色器

#version 330 core

layout(location = 0) in vec3 aPosition;

void main(void)
{
    gl_Position = vec4(aPosition, 1.0);
}

片段着色器

#version 330

out vec4 outputColor;

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

运行程序可以得到下面的结果：

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