RenderStreamPBO.java

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package org.lwjgl.util.stream;

import org.lwjgl.BufferUtils;
import org.lwjgl.opengl.ContextCapabilities;
import org.lwjgl.opengl.GLContext;

import static org.lwjgl.opengl.GL11.*;
import static org.lwjgl.opengl.GL12.*;
import static org.lwjgl.opengl.GL15.*;
import static org.lwjgl.opengl.GL21.*;
import static org.lwjgl.opengl.GL30.*;

/** Implements streaming PBO updates from a framebuffer object. */
abstract class RenderStreamPBO extends StreamBufferedPBO implements RenderStream {

	public static enum ReadbackType {
		/** RenderBuffers on FBO, ReadPixels to readback. */
		READ_PIXELS,
		/** Textures on FBO, GetTexImage to readback. */
		GET_TEX_IMAGE
	}

	private final ReadbackType readbackType;

	protected final StreamUtil.FBOUtil fboUtil;
	private final   int                renderFBO;

	private int samples;

	private int rgbaBuffer;
	private int depthBuffer;

	private int msaaResolveFBO;
	private int msaaResolveBuffer;

	protected int synchronousFrames;

	protected RenderStreamPBO(final StreamHandler handler, final int samples, final int transfersToBuffer, final ReadbackType readbackType) {
		super(handler, transfersToBuffer);

		this.readbackType = readbackType;

		final ContextCapabilities caps = GLContext.getCapabilities();

		fboUtil = StreamUtil.getFBOUtil(caps);
		renderFBO = fboUtil.genFramebuffers();

		this.samples = StreamUtil.checkSamples(samples, caps);
	}

	public StreamHandler getHandler() {
		return handler;
	}

	private void resize(final int width, final int height) {
		if ( width < 0 || height < 0 )
			throw new IllegalArgumentException("Invalid dimensions: " + width + " x " + height);

		destroyObjects();

		this.width = width;
		this.height = height;

		this.stride = StreamUtil.getStride(width);

		if ( width == 0 || height == 0 )
			return;

		bufferIndex = synchronousFrames = transfersToBuffer - 1;

		// Setup render FBO

		fboUtil.bindFramebuffer(GL_DRAW_FRAMEBUFFER, renderFBO);

		if ( samples <= 1 && readbackType == ReadbackType.GET_TEX_IMAGE )
			fboUtil.framebufferTexture2D(
				GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
				rgbaBuffer = StreamUtil.createRenderTexture(width, height), 0
			);
		else
			fboUtil.framebufferRenderbuffer(
				GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER,
				rgbaBuffer = StreamUtil.createRenderBuffer(fboUtil, width, height, samples, GL_RGBA8)
			);

		fboUtil.framebufferRenderbuffer(
			GL_DRAW_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER,
			depthBuffer = StreamUtil.createRenderBuffer(fboUtil, width, height, samples, GL_DEPTH24_STENCIL8)
		);

		glViewport(0, 0, width, height);

		fboUtil.bindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);

		if ( 1 < samples ) {
			// Setup MSAA resolve FBO

			if ( msaaResolveFBO == 0 ) msaaResolveFBO = fboUtil.genFramebuffers();

			fboUtil.bindFramebuffer(GL_READ_FRAMEBUFFER, msaaResolveFBO);

			if ( readbackType == ReadbackType.READ_PIXELS )
				fboUtil.framebufferRenderbuffer(
					GL_READ_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER,
					msaaResolveBuffer = StreamUtil.createRenderBuffer(fboUtil, width, height, GL_RGBA8)
				);
			else
				fboUtil.framebufferTexture2D(
					GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
					msaaResolveBuffer = StreamUtil.createRenderTexture(width, height), 0
				);

			fboUtil.bindFramebuffer(GL_READ_FRAMEBUFFER, 0);
		} else if ( msaaResolveFBO != 0 ) {
			if ( readbackType == ReadbackType.READ_PIXELS )
				fboUtil.deleteRenderbuffers(msaaResolveBuffer);
			else
				glDeleteTextures(msaaResolveBuffer);
			msaaResolveBuffer = 0;

			fboUtil.deleteFramebuffers(msaaResolveFBO);
			msaaResolveFBO = 0;
		}

		// Setup read-back buffers

		resizeBuffers(height, stride);
	}

	protected void resizeBuffers(final int height, final int stride) {
		super.resizeBuffers(height, stride, GL_PIXEL_PACK_BUFFER, GL_STREAM_READ);
	}

	public void bind() {
		if ( this.width != handler.getWidth() || this.height != handler.getHeight() )
			resize(handler.getWidth(), handler.getHeight());

		fboUtil.bindFramebuffer(GL_DRAW_FRAMEBUFFER, renderFBO);
	}

	protected void prepareFramebuffer() {
		if ( msaaResolveFBO == 0 )
			fboUtil.bindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);
		else {
			// Resolve MSAA
			fboUtil.bindFramebuffer(GL_READ_FRAMEBUFFER, renderFBO);
			fboUtil.bindFramebuffer(GL_DRAW_FRAMEBUFFER, msaaResolveFBO);
			fboUtil.blitFramebuffer(0, 0, width, height, 0, 0, width, height, GL_COLOR_BUFFER_BIT, GL_NEAREST);
			fboUtil.bindFramebuffer(GL_DRAW_FRAMEBUFFER, 0);
			fboUtil.bindFramebuffer(GL_READ_FRAMEBUFFER, 0);
		}
	}

	public void swapBuffers() {
		if ( width == 0 || height == 0 )
			return;

		prepareFramebuffer();

		final int trgPBO = (int)(bufferIndex % transfersToBuffer);
		final int srcPBO = (int)((bufferIndex - 1) % transfersToBuffer);

		glBindBuffer(GL_PIXEL_PACK_BUFFER, pbos[trgPBO]);

		// Back-pressure. Make sure we never buffer more than <transfersToBuffer> frames ahead.
		if ( processingState.get(trgPBO) )
			waitForProcessingToComplete(trgPBO);

		readBack(trgPBO);

		// This will be non-zero for the first (transfersToBuffer - 1) frames
		// after start-up or a resize.
		if ( 0 < synchronousFrames ) {
			// The srcPBO is currently empty. Wait for trgPBO's ReadPixels to complete and copy the current frame to srcPBO.
			// We do this to avoid sending an empty buffer for processing, which would cause a visible flicker on resize.
			copyFrames(trgPBO, srcPBO);
			synchronousFrames--;
		}

		// Time to process the srcPBO

		pinBuffer(srcPBO);

		// Send the buffer for processing

		processingState.set(srcPBO, true);
		semaphores[srcPBO].acquireUninterruptibly();

		handler.process(
			width, height,
			pinnedBuffers[srcPBO],
			stride,
			semaphores[srcPBO]
		);

		bufferIndex++;
	}

	protected void readBack(final int index) {
		// Stride in pixels
		glPixelStorei(GL_PACK_ROW_LENGTH, stride >> 2);

		// Asynchronously transfer current frame
		if ( readbackType == ReadbackType.READ_PIXELS ) {
			fboUtil.bindFramebuffer(GL_READ_FRAMEBUFFER, msaaResolveFBO == 0 ? renderFBO : msaaResolveFBO);
			glReadPixels(0, 0, width, height, GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, 0);
			fboUtil.bindFramebuffer(GL_READ_FRAMEBUFFER, 0);
		} else {
			glBindTexture(GL_TEXTURE_2D, msaaResolveFBO == 0 ? rgbaBuffer : msaaResolveBuffer);
			glGetTexImage(GL_TEXTURE_2D, 0, GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, 0);
			glBindTexture(GL_TEXTURE_2D, 0);
		}

		// Restore PACK_ROW_LENGTH
		glPixelStorei(GL_PACK_ROW_LENGTH, 0);
	}

	protected abstract void copyFrames(final int src, final int trg);

	protected abstract void pinBuffer(final int index);

	protected void destroyObjects() {
		for ( int i = 0; i < semaphores.length; i++ ) {
			if ( processingState.get(i) ) {
				glBindBuffer(GL_PIXEL_PACK_BUFFER, pbos[i]);
				waitForProcessingToComplete(i);
			}
		}

		glBindBuffer(GL_PIXEL_PACK_BUFFER, 0);

		for ( int i = 0; i < pbos.length; i++ ) {
			if ( pbos[i] != 0 )
				glDeleteBuffers(pbos[i]);
		}

		if ( msaaResolveBuffer != 0 ) {
			if ( readbackType == ReadbackType.READ_PIXELS )
				fboUtil.deleteRenderbuffers(msaaResolveBuffer);
			else
				glDeleteTextures(msaaResolveBuffer);
		}
		if ( depthBuffer != 0 ) fboUtil.deleteRenderbuffers(depthBuffer);
		if ( rgbaBuffer != 0 ) {
			if ( samples <= 1 && readbackType == ReadbackType.GET_TEX_IMAGE )
				glDeleteTextures(rgbaBuffer);
			else
				fboUtil.deleteRenderbuffers(rgbaBuffer);
		}
	}

	public void destroy() {
		destroyObjects();

		if ( msaaResolveFBO != 0 )
			fboUtil.deleteFramebuffers(msaaResolveFBO);
		fboUtil.deleteFramebuffers(renderFBO);
	}

}