之前我们已经提及了如何在空间中绘制三条线段，使它们相互组合看起来像是一个三角形。这里我们来画一个真正意义上的三角形。

  1. 创建主程序中的类
using OpenTK.Mathematics;
using OpenTK.Windowing.Desktop;

namespace OpenTK_Tutorials
{
    public static class Program
    {
        private static void Main()
        {
            var nativeWindowSettings = new NativeWindowSettings()
            {
                Size = new Vector2i(800, 600),
                Title = "Draw Triangle",
            };

            using (var game = new Game(GameWindowSettings.Default, nativeWindowSettings))
            {
                game.Run();
            }
        }
    }
}
  1. 构建主程序中调用的​​GUI​​窗口界面的类
using OpenTK_Tutorials.Common;
using OpenTK.Graphics.OpenGL4;
using OpenTK.Windowing.Common;
using OpenTK.Windowing.GraphicsLibraryFramework;
using OpenTK.Windowing.Desktop;

namespace OpenTK_Tutorials
{
    public class Game : GameWindow
    {
        private readonly float[] _vertices =
        {
            -0.5f, -0.5f, 0.0f, // 左下角端点
             0.5f, -0.5f, 0.0f, // 右下角端点
             0.0f,  0.5f, 0.0f  // 顶部端点
        };

        private int _vertexBufferObject;

        private int _vertexArrayObject;

        private Shader _shader;

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

        protected override void OnLoad()
        {
            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);

            // 注意此时我们选择渲染图元的类型为PrimitiveType.Triangles，这样绘图才会完成对三角形的填充效果
            GL.DrawArrays(PrimitiveType.Triangles, 0, 3);

            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);

            GL.DeleteBuffer(_vertexBufferObject);
            GL.DeleteVertexArray(_vertexArrayObject);

            GL.DeleteProgram(_shader.Handle);
            base.OnUnload();
        }
    }
}
  1. 着色器类
using System;
using System.IO;
using System.Text;
using System.Collections.Generic;
using OpenTK.Graphics.OpenGL4;
using OpenTK.Mathematics;

namespace OpenTK_Tutorials.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);
        }
    }
}
  1. 端点着色器
#version 330 core

layout(location = 0) in vec3 aPosition;

void main(void)
{
    gl_Position = vec4(aPosition, 1.0);
}
  1. 片段着色器
#version 330

out vec4 outputColor;

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

对比之前的文章，端点着色器以及片段着色器中的内容没有变化。

运行程序可以得到下面的结果：

OpenTK---空间中三角形的绘制_着色器


码字不易，如果大家觉得有用，请高抬贵手给一个赞让我上推荐让更多的人看到吧~