[3.0.0] Using compositor global textures

[Nimble]

Ogre Version: 3.0.0

I'm trying to use a global texture in a compositor. Defining the texture seems to work fine but I can't work out how to use it as a render target.

This is what I'm trying:

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compositor_node Final
{
	in 0 rt_out
	target global_rt
	{
		pass clear {}
	}
	target rt_out
	{
		pass clear {}
	}
}

workspace ExampleWorkspace
{
	texture global_rt target_width target_height PFG_RGBA16_FLOAT msaa_auto
	connect_external 0 Final 0
}

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An exception has occured: OGRE EXCEPTION(5:ItemIdentityException): Could not find RenderTargetView with name global_rt in CompositorNodeDef::getRenderTargetViewDef at ~/ogre-next/OgreMain/src/Compositor/OgreTextureDefinition.cpp (line 255)

[dark_sylinc]

It's been a while since I've used global textures: Since global textures are everywhere and RTVs need to be defined explicitly, OgreNext is currently not autogenerating the RTVs for the nodes that need it. But you can write one yourself:

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compositor_node Final
{
	in 0 rt_out

   rtv my_rtv
   {
          color global_rt
   }

target my_rtv
{
	pass clear {}
}
target rt_out
{
	pass clear {}
}
}

workspace ExampleWorkspace
{
	texture global_rt target_width target_height PFG_RGBA16_FLOAT msaa_auto
	connect_external 0 Final 0
}

See the full syntax in the manual.

HINT: Rather than using a global texture you may find it more useful to create an empty node that just defines textures and outputs them, like this:

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compositor_node TextureOwner
{
	texture my_own_rt target_width target_height PFG_RGBA16_FLOAT msaa_auto
	out 0 my_own_rt
}

compositor_node Final
{
	in 0 rt_out
	in 1 my_own_rt

target my_own_rt
{
	pass clear {}
}
target rt_out
{
	pass clear {}
}
}

workspace ExampleWorkspace
{
	connect 0 TextureOwner 1 Final
	connect_external 0 Final 0
}

This is more flexible because when you need to modify your graphics settings and thus the Compositor, you can rewire some nodes with the additional textures (specially true for MSAA because MSAA often requires extra textures to be handled as a special case). Having global texture names means that if you suddenly wish Node A and Node B to have a different texture, you must change the script for both nodes. But with this approach, you can just rewire Node B to source its texture from a different node; which can happen at runtime if graphics settings change.

[Nimble]

Ah, okay, that helps. I get this error:

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An exception has occured: OGRE EXCEPTION(5:ItemIdentityException): Can't find texture with name: 'global_rt' If it's a global texture, trying to use it in the output channel will fail. in CompositorNodeDef::getTextureSource at ~/ogre-next/OgreMain/src/Compositor/OgreTextureDefinition.cpp (line 214)

But this works:

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rtv global_rt {}
target global_rt {}

rtv my_rtv
{
	colour global_rt
}

Unfortunately I'm getting another problem with global textures. A global texture and a local texture both defined with "target_width target_height" do not always have the same dimensions. When resizing, the local texture is resized first. So something like this fails:

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rtv my_rtv
{
	colour local_rt
	stencil global_stencil
}

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An exception has occured: OGRE EXCEPTION(2:InvalidParametersException): Manually specified depth buffer 'stencil[Value 0x00000000]' is incompatible with colour RTT #0'local_rt[Value 0x0000000a]
Colour: 1278x700x1 1x MSAA PFG_RGBA16_FLOAT
Depth: 1280x720x1 1x MSAA PFG_D32_FLOAT_S8X24_UINT in RenderPassDescriptor::entriesModified at ~/ogre-next/OgreMain/src/OgreRenderPassDescriptor.cpp (line 277)