public static unsafe Texture2D CreateFromStreamUnsynchronized(RenderContext renderContext, Stream stream)
{
using var image = Image.Load <Rgba32>(stream);
image.Mutate(x => x.Flip(FlipMode.Vertical));
var texture = new Texture2D(renderContext)
{
Width = image.Width,
Height = image.Height,
};
var span = image.GetPixelSpan();
int size = span.Length * sizeof(Rgba32);
fixed(void *data = &MemoryMarshal.GetReference(span))
{
var start = new IntPtr(data);
using var pixelBuffer = PixelBuffer.Create <Rgba32>(renderContext, size, true, true);
GLHandle prevPixelBuffer = (GLHandle)GL.GetInteger(GetPName.PixelUnpackBufferBinding);
GL.BindBuffer(BufferTarget.PixelUnpackBuffer, pixelBuffer.Handle);
// When we load assets asynchronously, using SubData to set the data will cause the main thread
// to wait for the GL call to complete, so we use a PBO and fill it with a mapped memory range to
// prevent OpenGL synchronization from causing frame drops on the main thread.
IntPtr pixelPointer = GL.MapBufferRange(BufferTarget.PixelUnpackBuffer,
IntPtr.Zero,
size,
BufferAccessMask.MapWriteBit
| BufferAccessMask.MapUnsynchronizedBit
| BufferAccessMask.MapInvalidateRangeBit);
if (pixelPointer == IntPtr.Zero)
{
throw new GraphicsContextException("Could not map PixelUnbackBuffer range.");
}
// We send the data to mapped memory in multiple batches instead of one large one for the same
// reason.
int remaining = size;
const int step = 2048;
while (remaining > 0)
{
int currentStep = Math.Min(remaining, step);
int point = size - remaining;
void *dest = (void *)IntPtr.Add(pixelPointer, point);
void *src = (void *)IntPtr.Add(start, point);
Unsafe.CopyBlock(dest, src, (uint)currentStep);
remaining -= step;
}
GL.UnmapBuffer(BufferTarget.PixelUnpackBuffer);
if (GLInfo.HasDirectStateAccess)
{
GL.TextureStorage2D(texture.Handle,
1,
SizedInternalFormat.Rgba8,
texture.Width,
texture.Height);
GL.TextureSubImage2D(texture.Handle,
0,
0,
0,
texture.Width,
texture.Height,
PixelFormat.Rgba,
PixelType.UnsignedByte,
IntPtr.Zero);
GL.GenerateTextureMipmap(texture.Handle);
}
else
{
var previousTexture = renderContext.TextureUnits[0].Texture2D;
renderContext.BindTexture(0, texture);
GL.TexImage2D(TextureTarget.Texture2D,
0,
PixelInternalFormat.Rgba,
texture.Width,
texture.Height,
0,
PixelFormat.Rgba,
PixelType.UnsignedByte,
IntPtr.Zero);
GL.GenerateMipmap(GenerateMipmapTarget.Texture2D);
renderContext.BindTexture(0, previousTexture);
}
GL.BindBuffer(BufferTarget.PixelUnpackBuffer, prevPixelBuffer);
}
texture.SetDefaultTextureParameters(renderContext);
// TODO: Look into if this is necessary (?)
GL.Finish();
return(texture);
}