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GL backend: Fix an issue with discardEnd flags

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In OpenGL with use glInvalidateFramebuffer() for hinting controlling
the load/store of tiles. However, glInvalidateFramebuffer() conceptually
destroys the content of the framebuffer attachment.

This causes a problem when we want for instance to use a buffer for
reading only (e.g. a depth buffer) in multiple passes. In such
scenario, the attachment will be marked as "discard" (which is a
misnomer for storeOp==DONT_CARE in vulkan parlance), without the
intention of making the buffer invalid.

We fix this by ignoring the discardEnd flags entirely if a buffer
has not been written. In this case, we relying on the driver to not
write the tiles out -- but we don't have any other way to express
this in GL.

This issue cannot be encountered currently because the framegraph 
is not aggressive enough setting the discardEnd flags.
This commit is contained in:
Pixelflinger
2020-04-30 14:03:39 -07:00
committed by Mathias Agopian
parent 8c7fbb2e01
commit b514b2e996
2 changed files with 16 additions and 1 deletions
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13
filament/backend/src/opengl/OpenGLDriver.cpp
View File

@@ -2092,6 +2092,10 @@ void OpenGLDriver::beginRenderPass(Handle<HwRenderTarget> rth,
params.clearColor, params.clearDepth, params.clearStencil);
}
// we need to reset those after we call clearWithRasterPipe()
mRenderPassColorWrite = any(clearFlags & TargetBufferFlags::COLOR_ALL);
mRenderPassDepthWrite = any(clearFlags & TargetBufferFlags::DEPTH);
gl.viewport(params.viewport.left, params.viewport.bottom,
params.viewport.width, params.viewport.height);
@@ -2112,11 +2116,18 @@ void OpenGLDriver::endRenderPass(int) {
GLRenderTarget const* const rt = handle_cast<GLRenderTarget*>(mRenderPassTarget);
const TargetBufferFlags discardFlags = mRenderPassParams.flags.discardEnd & rt->targets;
TargetBufferFlags discardFlags = mRenderPassParams.flags.discardEnd & rt->targets;
if (rt->gl.fbo_read) {
resolvePass(ResolveAction::STORE, rt, discardFlags);
}
if (!mRenderPassColorWrite) {
discardFlags &= ~TargetBufferFlags::COLOR_ALL;
}
if (!mRenderPassDepthWrite) {
discardFlags &= ~TargetBufferFlags::DEPTH;
}
// glInvalidateFramebuffer appeared on GLES 3.0 and GL4.3, for simplicity we just
// ignore it on GL (rather than having to do a runtime check).
if (GLES30_HEADERS) {

4
filament/backend/src/opengl/OpenGLDriver.h
View File

@@ -316,6 +316,8 @@ private:
void setRasterStateSlow(backend::RasterState rs) noexcept;
void setRasterState(backend::RasterState rs) noexcept {
mRenderPassColorWrite |= rs.colorWrite;
mRenderPassDepthWrite |= rs.depthWrite;
if (UTILS_UNLIKELY(rs != mRasterState)) {
setRasterStateSlow(rs);
}
@@ -374,6 +376,8 @@ private:
// state required to represent the current render pass
backend::Handle<backend::HwRenderTarget> mRenderPassTarget;
backend::RenderPassParams mRenderPassParams;
GLboolean mRenderPassColorWrite{};
GLboolean mRenderPassDepthWrite{};
void clearWithRasterPipe(backend::TargetBufferFlags clearFlags,
math::float4 const& linearColor, GLfloat depth, GLint stencil) noexcept;