/
webgl_example.go
156 lines (126 loc) · 4.33 KB
/
webgl_example.go
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package main
import (
"github.com/gopherjs/gopherjs/js"
"github.com/gopherjs/webgl"
)
const vertexShaderSource = `
attribute vec2 a_position;
attribute vec4 a_color;
uniform vec2 u_resolution;
varying vec4 v_color;
void main() {
// convert the position from pixels to 0.0 to 1.0
vec2 zeroToOne = a_position / u_resolution;
// convert from 0->1 to 0->2
vec2 zeroToTwo = zeroToOne * 2.0;
// convert from 0->2 to -1->+1 (clipspace)
vec2 clipSpace = zeroToTwo - 1.0;
gl_Position = vec4(clipSpace * vec2(1, -1), 0, 1);
v_color = a_color;
}
`
const fragShaderSource = `
precision mediump float;
varying vec4 v_color;
void main() {
gl_FragColor = v_color;
}
`
func main() {
document := js.Global.Get("document")
canvas := document.Call("createElement", "canvas")
document.Get("body").Call("appendChild", canvas)
js.Global.Get("console").Call("log", "running webgl_example!")
attrs := webgl.DefaultAttributes()
attrs.Alpha = false
gl, err := webgl.NewContext(canvas, attrs)
if err != nil {
js.Global.Call("alert", "Error: "+err.Error())
return
}
// init shader program
shader, ok := initShader(gl, canvas)
if !ok { return }
// set blend function for when alpha blending is enabled
gl.BlendFuncSeparate(
gl.SRC_ALPHA, gl.ONE_MINUS_SRC_ALPHA, gl.ZERO, gl.ONE)
gl.Enable(gl.BLEND)
// get gl shader variables
uResolution := gl.GetUniformLocation(shader, "u_resolution")
aPosition := gl.GetAttribLocation(shader, "a_position")
gl.EnableVertexAttribArray(aPosition)
aColor := gl.GetAttribLocation(shader, "a_color")
gl.EnableVertexAttribArray(aColor)
// set viewport
setResolution(gl, canvas, uResolution)
// draw something
gl.ClearColor(0.0, 1.0, 1.0, 1.0) // cyanish
gl.Clear(gl.COLOR_BUFFER_BIT)
vertices := []float32{
16.0, 16.0,
128.0, 16.0,
128.0, 128.0,
128.0, 128.0,
16.0, 128.0,
16.0, 16.0}
vrtxBuff := gl.CreateBuffer()
gl.BindBuffer(gl.ARRAY_BUFFER, vrtxBuff)
gl.BufferData(gl.ARRAY_BUFFER, vertices, gl.STATIC_DRAW)
gl.VertexAttribPointer(aPosition, 2, gl.FLOAT, false, 0, 0)
rgba := []float32{
1.0, 0.0, 0.0, 0.7, // reddish
1.0, 0.0, 0.0, 0.7,
1.0, 0.0, 0.0, 0.7,
1.0, 0.0, 0.0, 0.7,
1.0, 0.0, 0.0, 0.7,
1.0, 0.0, 0.0, 0.7}
rgbaBuff := gl.CreateBuffer()
gl.BindBuffer(gl.ARRAY_BUFFER, rgbaBuff)
gl.BufferData(gl.ARRAY_BUFFER, rgba, gl.STATIC_DRAW)
gl.VertexAttribPointer(aColor, 4, gl.FLOAT, false, 0, 0)
gl.DrawArrays(gl.TRIANGLES, 0, 6);
}
func initShader(gl *webgl.Context, canvas *js.Object) (*js.Object, bool) {
shader := gl.CreateProgram()
vertexShader, ok := getShader(gl, gl.VERTEX_SHADER, vertexShaderSource)
if !ok {
js.Global.Call("alert", "Error getting vertex shader")
return nil, false
}
fragShader, ok := getShader( gl, gl.FRAGMENT_SHADER, fragShaderSource)
if !ok {
js.Global.Call("alert", "Error getting fragment shader")
return nil, false
}
gl.AttachShader(shader, vertexShader)
gl.AttachShader(shader, fragShader)
gl.LinkProgram(shader)
if !gl.GetProgramParameterb(shader, gl.LINK_STATUS) {
js.Global.Call("alert", "couldnt init shaders :(")
return nil, false
}
gl.UseProgram(shader)
return shader, true
}
func setResolution(
gl *webgl.Context, canvas *js.Object, uResolution *js.Object) {
width := canvas.Get("clientWidth").Int()
height := canvas.Get("clientHeight").Int()
if (canvas.Get("width").Int() != width) ||
(canvas.Get("height").Int() != height) {
canvas.Set("width", width)
canvas.Set("height", height)
}
gl.Viewport(0, 0, width, height);
gl.Uniform2f(uResolution, float32(width), float32(height))
}
func getShader(gl *webgl.Context, typ int, source string) (*js.Object, bool) {
shader := gl.CreateShader(typ)
gl.ShaderSource(shader, source)
gl.CompileShader(shader)
if !gl.GetShaderParameter(shader, gl.COMPILE_STATUS).Bool() {
js.Global.Call("alert", gl.GetShaderInfoLog(shader))
return nil, false
}
return shader, true
}