glutils.go

package glutils

import (
	"fmt"
	"unsafe"
	"shader"
	"github.com/go-gl/gl/v3.3-core/gl"
	"github.com/go-gl/glfw/v3.2/glfw"
)

const (
	sizeOfFloat = 4
	sizeOfUInt32 = 4
)

func InitOpenGL() error {
	if err := gl.Init(); err != nil {
		panic(err)
	}
	version := gl.GoStr(gl.GetString(gl.VERSION))
	fmt.Println("OpenGL Version", version)
	gl.ClearColor(0, 0, 0, 1)
	gl.PolygonMode(gl.FRONT_AND_BACK, gl.FILL)
	return nil
}

func ProcessInput(window *glfw.Window){
	if(window.GetKey(glfw.KeyEscape) == glfw.Press){
		window.SetShouldClose(true)
	}
}

func MakeVertexArrayObject(vertices []float32, indices []uint32) uint32 {
	var vao uint32
	var vbo uint32
	var ebo uint32
	gl.GenVertexArrays(1, &vao)
	gl.BindVertexArray(vao)
	gl.GenBuffers(1, &vbo)
	gl.BindBuffer(gl.ARRAY_BUFFER, vbo)
	gl.BufferData(gl.ARRAY_BUFFER, sizeOfFloat * len(vertices), gl.Ptr(vertices), gl.STATIC_DRAW)
	gl.GenBuffers(1, &ebo)
	gl.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, ebo)
	gl.BufferData(gl.ELEMENT_ARRAY_BUFFER, sizeOfUInt32 * len(indices), gl.Ptr(indices), gl.STATIC_DRAW) 
	gl.VertexAttribPointer(0, 3, gl.FLOAT, false, 6*sizeOfFloat, gl.PtrOffset(0))
	gl.EnableVertexAttribArray(0)
	gl.VertexAttribPointer(1, 3, gl.FLOAT, false, 6 * sizeOfFloat, gl.PtrOffset(3 * sizeOfFloat))
	gl.EnableVertexAttribArray(1)
	gl.BindVertexArray(0)
	gl.BindBuffer(gl.ARRAY_BUFFER, 0)
	gl.BindBuffer(gl.ELEMENT_ARRAY_BUFFER, 0)
	return vao
}

func GetGlfwWindow(name string, width int, height int) (*glfw.Window, error) {
	err := glfw.Init()
	if err != nil {
		return nil, err
	}
	glfw.WindowHint(glfw.Samples, 0)
	glfw.WindowHint(glfw.Resizable, glfw.True)
	glfw.WindowHint(glfw.ContextVersionMajor, 3)
	glfw.WindowHint(glfw.ContextVersionMinor, 3)
	glfw.WindowHint(glfw.OpenGLProfile, glfw.OpenGLCoreProfile)
	glfw.WindowHint(glfw.OpenGLForwardCompatible, glfw.True)
	window, err := glfw.CreateWindow(width, height, name, nil, nil)
	if err != nil {
		return nil, err
	}
	window.MakeContextCurrent()
	window.SetInputMode(glfw.StickyKeysMode, gl.TRUE)
	return window, nil
}

func DrawVAO(vao uint32, window *glfw.Window, program *shader.Shader, count int32){
	gl.Clear(gl.COLOR_BUFFER_BIT)
	program.Use()
	gl.BindVertexArray(vao)
	gl.DrawElements(gl.TRIANGLES, count, gl.UNSIGNED_INT,unsafe.Pointer(nil))
	window.SwapBuffers()
}