func sliceMap2Float32Buffer(mode uint32, length int) ([][2]float32, error) {
data := gl.MapBuffer(gl.ARRAY_BUFFER, mode)
if data == nil {
return nil, fmt.Errorf("buffer data pointer is nil")
}
header := reflect.SliceHeader{
Data: uintptr(data),
Len: length,
Cap: length,
}
return *((*[][2]float32)(unsafe.Pointer(&header))), nil
}
func sliceMapParticlesBuffer(mode uint32, length int) ([]gpuParticle, error) {
data := gl.MapBuffer(gl.SHADER_STORAGE_BUFFER, mode)
if data == nil {
return nil, fmt.Errorf("buffer data pointer is nil")
}
header := reflect.SliceHeader{
Data: uintptr(data),
Len: length,
Cap: length,
}
slice := (*[]gpuParticle)(unsafe.Pointer(&header))
return *slice, nil
}
func (s *MainState) Render() error {
program := s.program
gl.UseProgram(program)
projectionUniform := gl.GetUniformLocation(program, gl.Str("projection\x00"))
gl.UniformMatrix4fv(projectionUniform, 1, false, &projection[0])
gl.Flush()
buffer := s.vertexBuffer
gl.BindBuffer(gl.ARRAY_BUFFER, buffer)
gl.BufferData(
gl.ARRAY_BUFFER,
int(PARTICLE_COUNT_DEFAULT*unsafe.Sizeof([2]float32{})),
nil,
gl.STREAM_DRAW)
dataPointer := gl.MapBuffer(gl.ARRAY_BUFFER, gl.WRITE_ONLY)
if dataPointer == nil {
return fmt.Errorf("buffer data pointer is nil")
}
data := (*[PARTICLE_COUNT_DEFAULT][2]float32)(dataPointer)
gl.ClearColor(0, 0, 0, 1)
gl.Clear(gl.COLOR_BUFFER_BIT)
for i := range data {
p := s.space.Particle(i)
if p == nil {
return fmt.Errorf("no particle of id %d", i)
}
data[i][0] = float32(p.Position.X)
data[i][1] = float32(p.Position.Y)
}
gl.UnmapBuffer(gl.ARRAY_BUFFER)
gl.DrawArrays(gl.POINTS, 0, PARTICLE_COUNT_DEFAULT)
return nil
}