Golang游戏引擎日记（06.绘制一个三角形）

现在开始绘制一个三角形，效果如下图：

 game.go：

package engine

import (
	"fmt"
	"unsafe"

	"github.com/go-gl/gl/v3.3-core/gl"
	"github.com/go-gl/glfw/v3.3/glfw"
)

var mIsRunning = false
var mWidth = 1024
var mHeight = 768

var vertices = [...]float32{
	-0.5, -0.5, 0.0,
	0.5, -0.5, 0.0,
	0.0, 0.5, 0.0,
}

var vertexShaderSource = `
#version 330 core
layout (location = 0) in vec3 aPos;

void main()
{
    gl_Position = vec4(aPos.x, aPos.y, aPos.z, 1.0);
}
`

var fragmentShaderSource = `
#version 330 core
out vec4 FragColor;

void main()
{
    FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);
} 
`

type Game struct {
	MWindow *glfw.Window
}

//初始化引擎
func (g *Game) Initialize() bool {
	//获取glfw版本
	fmt.Println(glfw.GetVersionString())
	//初始化glfw
	var err error
	if err = glfw.Init(); err != nil {
		fmt.Printf("Unable to initialize glfw: %v", err)
		return false
	}

	glfw.WindowHint(glfw.RedBits, 8)
	glfw.WindowHint(glfw.GreenBits, 8)
	glfw.WindowHint(glfw.BlueBits, 8)
	glfw.WindowHint(glfw.AlphaBits, 8)
	glfw.WindowHint(glfw.DepthBits, 24)
	glfw.WindowHint(glfw.DoubleBuffer, 1)
	//glfw.WindowHint(glfw.Resizable, 0) //禁止调整窗口大小
	//设置版本
	glfw.WindowHint(glfw.ContextVersionMajor, 3)
	glfw.WindowHint(glfw.ContextVersionMinor, 3)
	glfw.WindowHint(glfw.OpenGLProfile, glfw.OpenGLCoreProfile)
	glfw.WindowHint(glfw.OpenGLForwardCompatible, glfw.True)
	//窗口模式
	if g.MWindow, err = glfw.CreateWindow(mWidth, mHeight, "绘制一个三角形", nil, nil); err != nil {
		fmt.Printf("Failed to create window: %v", err)
		return false
	}
	//设置图标
	// if ok, _ := PathExists("./app.ico"); ok {
	// 	if f, err := os.Open("./app.ico"); err == nil {
	// 		defer f.Close()
	// 		if img, err := ico.Decode(f); err == nil {
	// 			g.MWindow.SetIcon([]image.Image{img})
	// 		}
	// 	}
	// }
	//回调函数
	g.MWindow.SetCloseCallback(CloseCallback) //关闭回调
	g.MWindow.SetSizeCallback(SizeCallback)   //调整回调
	g.MWindow.SetKeyCallback(KeyCallback)     //按键回调
	//上下文
	g.MWindow.MakeContextCurrent()

	//初始化opengl
	if err = gl.Init(); err != nil {
		fmt.Printf("Unable to initialize gl: %v", err)
		return false
	}
	gl.Viewport(0, 0, int32(mWidth), int32(mHeight))

	version := gl.GoStr(gl.GetString(gl.VERSION))
	fmt.Println(version)

	var VAO uint32
	gl.GenVertexArrays(1, &VAO)
	gl.BindVertexArray(VAO)

	var VBO uint32
	gl.GenBuffers(1, &VBO)
	gl.BindBuffer(gl.ARRAY_BUFFER, VBO)

	gl.BufferData(gl.ARRAY_BUFFER, int(unsafe.Sizeof(vertices)), unsafe.Pointer(&vertices), gl.STATIC_DRAW)
	//gl.BufferData(gl.ARRAY_BUFFER, len(vertices)*4, gl.Ptr(&vertices[0]), gl.STATIC_DRAW)

	//顶点着色器
	vertexShader := gl.CreateShader(gl.VERTEX_SHADER)
	vertexString, _ := gl.Strs(vertexShaderSource)
	gl.ShaderSource(vertexShader, 1, vertexString, nil)
	gl.CompileShader(vertexShader)
	//片段着色器
	fragmentShader := gl.CreateShader(gl.FRAGMENT_SHADER)
	fragmentString, _ := gl.Strs(fragmentShaderSource)
	gl.ShaderSource(fragmentShader, 1, fragmentString, nil)
	gl.CompileShader(fragmentShader)
	//着色器程序
	shaderProgram := gl.CreateProgram()
	gl.AttachShader(shaderProgram, vertexShader)
	gl.AttachShader(shaderProgram, fragmentShader)
	gl.LinkProgram(shaderProgram)
	gl.UseProgram(shaderProgram)
	//删除着色器
	gl.DeleteShader(vertexShader)
	gl.DeleteShader(fragmentShader)

	gl.VertexAttribPointerWithOffset(0, 3, gl.FLOAT, false, 3*int32(unsafe.Sizeof(float32(0))), uintptr(0))
	gl.EnableVertexAttribArray(0)

	//保持运行
	mIsRunning = true
	return true
}

//引擎循环
func (g *Game) RunLoop() {
	for mIsRunning {
		//清屏
		gl.ClearColor(0.2, 0.3, 0.3, 1.0)
		gl.Clear(gl.COLOR_BUFFER_BIT)
		//....
		g.ProcessInput()
		g.UpdateGame()
		g.GenerateOutput()
		//交换缓存
		g.MWindow.SwapBuffers()
		glfw.PollEvents()
	}
}

//引擎销毁
func (g *Game) Shutdown() {
	g.MWindow.Destroy()
	glfw.Terminate()
}

func (g *Game) ProcessInput() {

}

func (g *Game) UpdateGame() {

}

func (g *Game) GenerateOutput() {
	gl.DrawArrays(gl.TRIANGLES, 0, 3)
}

func CloseCallback(w *glfw.Window) {
	mIsRunning = false
}

func SizeCallback(w *glfw.Window, width int, height int) {
	gl.Viewport(0, 0, int32(width), int32(height))
}

func KeyCallback(w *glfw.Window, key glfw.Key, scancode int, action glfw.Action, mods glfw.ModifierKey) {
	switch key {
	case glfw.KeyEscape:
		if action == glfw.Press {
			CloseCallback(w)
		}
	}
}