/
charactershadow.go
132 lines (104 loc) · 3.33 KB
/
charactershadow.go
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package main
import (
"encoding/binary"
"fmt"
"math"
"github.com/go-gl/mathgl/mgl32"
"github.com/goxjs/gl"
"golang.org/x/mobile/exp/f32"
)
type characterShadow struct {
vertexCount int
program gl.Program
pMatrixUniform gl.Uniform
mvMatrixUniform gl.Uniform
vertexPositionAttribute gl.Attrib
vertexAlphaAttribute gl.Attrib
vertexPositionBuffer gl.Buffer
vertexAlphaBuffer gl.Buffer
}
func newCharacterShadow() (*characterShadow, error) {
l := new(characterShadow)
const (
vertexSource = `//#version 120 // OpenGL 2.1.
//#version 100 // WebGL.
uniform mat4 uMVMatrix;
uniform mat4 uPMatrix;
attribute vec3 aVertexPosition;
attribute float aVertexAlpha;
varying float vPixelAlpha;
void main() {
vPixelAlpha = aVertexAlpha;
gl_Position = uPMatrix * uMVMatrix * vec4(aVertexPosition, 1.0);
}
`
fragmentSource = `//#version 120 // OpenGL 2.1.
//#version 100 // WebGL.
#ifdef GL_ES
precision lowp float;
#endif
varying float vPixelAlpha;
void main() {
gl_FragColor = vec4(0, 0, 0, vPixelAlpha);
}
`
)
var err error
l.program, err = createValidateUseProgram(vertexSource, fragmentSource)
if err != nil {
return nil, err
}
l.pMatrixUniform = gl.GetUniformLocation(l.program, "uPMatrix")
l.mvMatrixUniform = gl.GetUniformLocation(l.program, "uMVMatrix")
l.vertexPositionAttribute = gl.GetAttribLocation(l.program, "aVertexPosition")
l.vertexAlphaAttribute = gl.GetAttribLocation(l.program, "aVertexAlpha")
positionData := append([]float32{0, 0}, circle(mgl32.Vec2{}, mgl32.Vec2{16, 16}.Mul(1.75), 16)...)
l.vertexCount = len(positionData) / 2
l.vertexPositionBuffer = createVbo3Float(positionData)
alphaData := make([]uint8, l.vertexCount)
alphaData[0] = 76 // First vertex is the circle center, it has non-zero alpha. The rest are zero.
l.vertexAlphaBuffer = createVbo3Ubyte(alphaData)
if err := gl.GetError(); err != 0 {
return nil, fmt.Errorf("gl.GetError: %v", err)
}
return l, nil
}
func (l *characterShadow) setup() {
gl.UseProgram(l.program)
gl.BindBuffer(gl.ARRAY_BUFFER, l.vertexPositionBuffer)
gl.EnableVertexAttribArray(l.vertexPositionAttribute)
gl.VertexAttribPointer(l.vertexPositionAttribute, 2, gl.FLOAT, false, 0, 0)
gl.BindBuffer(gl.ARRAY_BUFFER, l.vertexAlphaBuffer)
gl.EnableVertexAttribArray(l.vertexAlphaAttribute)
gl.VertexAttribPointer(l.vertexAlphaAttribute, 1, gl.UNSIGNED_BYTE, true, 0, 0)
gl.Enable(gl.BLEND)
}
func (l *characterShadow) cleanup() {
gl.Disable(gl.BLEND)
gl.DisableVertexAttribArray(l.vertexPositionAttribute)
gl.DisableVertexAttribArray(l.vertexAlphaAttribute)
}
func (l *characterShadow) render() {
gl.DrawArrays(gl.TRIANGLE_FAN, 0, l.vertexCount)
}
func circle(pos mgl32.Vec2, size mgl32.Vec2, slices int) (vertices []float32) {
x := float64(slices)
for i := slices; i >= 0; i-- {
vertices = append(vertices,
pos[0]+float32(math.Sin(Tau*float64(i)/x))*size[0]/2,
pos[1]+float32(math.Cos(Tau*float64(i)/x))*size[1]/2)
}
return vertices
}
func createVbo3Float(data []float32) gl.Buffer {
vbo := gl.CreateBuffer()
gl.BindBuffer(gl.ARRAY_BUFFER, vbo)
gl.BufferData(gl.ARRAY_BUFFER, f32.Bytes(binary.LittleEndian, data...), gl.STATIC_DRAW)
return vbo
}
func createVbo3Ubyte(data []uint8) gl.Buffer {
vbo := gl.CreateBuffer()
gl.BindBuffer(gl.ARRAY_BUFFER, vbo)
gl.BufferData(gl.ARRAY_BUFFER, data, gl.STATIC_DRAW)
return vbo
}