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@@ -6,7 +6,7 @@ Screen-reading shaders
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Introduction
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~~~~~~~~~~~~
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-Very often, it is desired to make a shader that reads from the same
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+It is often desired to make a shader that reads from the same
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screen to which it's writing. 3D APIs, such as OpenGL or DirectX, make this very
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difficult because of internal hardware limitations. GPUs are extremely
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parallel, so reading and writing causes all sorts of cache and coherency
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@@ -15,7 +15,7 @@ properly.
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The workaround is to make a copy of the screen, or a part of the screen,
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to a back-buffer and then read from it while drawing. Godot provides a
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-few tools that make this process easy!
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+few tools that make this process easy.
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SCREEN_TEXTURE built-in texture
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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@@ -42,7 +42,7 @@ of blur at no cost.
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.. note::
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Mipmaps are not generated in GLES2 due to poor performance and compatibility with older
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- devices.
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+ devices.
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SCREEN_TEXTURE example
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~~~~~~~~~~~~~~~~~~~~~~
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@@ -101,13 +101,20 @@ With correct back-buffer copying, the two spheres blend correctly:
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.. image:: img/texscreen_demo2.png
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-In 3D, there is less flexibility to solve this particular issue because the
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-``SCREEN_TEXTURE`` is only captured once. Be careful when using
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+.. warning:
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+
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+ Materials that use ``SCREEN_TEXTURE`` are considered transparent themselves and
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+ will not appear in the resulting ``SCREEN_TEXTURE`` of other materials.
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+ If you plan to instance a scene that uses a material with ``SCREEN_TEXTURE``,
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+ you will need to use a BackBufferCopy node.
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+
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+In 3D, there is less flexibility to solve this particular issue because the
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+``SCREEN_TEXTURE`` is only captured once. Be careful when using
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``SCREEN_TEXTURE`` in 3D as it won't capture transparent objects and may capture
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some opaque objects that are in front of the object.
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You can reproduce the back-buffer logic in 3D by creating a :ref:`Viewport <class_Viewport>`
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-with a camera in the same position as your object, and then use the
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+with a camera in the same position as your object, and then use the
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:ref:`Viewport's <class_Viewport>` texture instead of ``SCREEN_TEXTURE``.
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Back-buffer logic
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@@ -136,7 +143,7 @@ Godot:
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DEPTH_TEXTURE
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~~~~~~~~~~~~~
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-For 3D Shaders, it's also possible to access the screen depth buffer. For this,
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+For 3D shaders, it's also possible to access the screen depth buffer. For this,
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the ``DEPTH_TEXTURE`` built-in is used. This texture is not linear; it must be
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converted via the inverse projection matrix.
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Hugo Locurcio