BGE: Various render improvements.

bge.logic.setRender(flag) to enable/disable render.
    The render pass is enabled by default but it can be disabled with
    bge.logic.setRender(False).
    Once disabled, the render pass is skipped and a new logic frame starts
    immediately. Note that VSync no longer limits the fps when render is off
    but the 'Use Frame Rate' option in the Render Properties still does.
    To run as many frames as possible, untick the option
    This function is useful when you don't need the default render, e.g.
    when doing offscreen render to an alternate device than the monitor.
    Note that without VSync, you must limit the frame rate by other means.

fbo = bge.render.offScreenCreate(width,height,[,samples=0][,target=bge.render.RAS_OFS_RENDER_BUFFER])
    Use this method to create an offscreen buffer of given size, with given MSAA
    samples and targetting either a render buffer (bge.render.RAS_OFS_RENDER_BUFFER)
    or a texture (bge.render.RAS_OFS_RENDER_TEXTURE). Use the former if you want to
    retrieve the frame buffer on the host and the latter if you want to pass the render
    to another context (texture are proper OGL object, render buffers aren't)
    The object created by this function can only be used as a parameter of the
    bge.texture.ImageRender() constructor to send the the render to the FBO rather
    than to the frame buffer. This is best suited when you want to create a render
    of specific size, or if you need an image with an alpha channel.

bge.texture.<imagetype>.refresh(buffer=None, format="RGBA", ts=-1.0)
    Without arg, the refresh method of the image objects is pretty much a no-op, it
    simply invalidates the image so that on next texture refresh, the image will
    be recalculated.
    It is now possible to pass an optional buffer object to transfer the image (and
    recalculate it if it was invalid) to an external object. The object must implement
    the 'buffer protocol'. The image will be transfered as "RGBA" or "BGRA" pixels
    depending on format argument (only those 2 formats are supported) and ts is an
    optional timestamp in the image depends on it (e.g. VideoFFmpeg playing a video file).
    With this function you don't need anymore to link the image object to a Texture
    object to use: the image object is self-sufficient.

bge.texture.ImageRender(scene, camera, fbo=None)
    Render to buffer is possible by passing a FBO object (see offScreenCreate).

bge.texture.ImageRender.render()
    Allows asynchronous render: call this method to render the scene but without
    extracting the pixels yet. The function returns as soon as the render commands
    have been send to the GPU. The render will proceed asynchronously in the GPU
    while the host can perform other tasks.
    To complete the render, you can either call refresh() directly of refresh the texture
    to which this object is the source. Asynchronous render is useful to achieve optimal
    performance: call render() on frame N and refresh() on frame N+1 to give as much as
    time as possible to the GPU to render the frame while the game engine can perform other tasks.

Support negative scale on camera.
    Camera scale was previously ignored in the BGE.
    It is now injected in the modelview matrix as a vertical or horizontal flip
    of the scene (respectively if scaleY<0 and scaleX<0).
    Note that the actual value of the scale is not used, only the sign.
    This allows to flip the image produced by ImageRender() without any performance
    degradation: the flip is integrated in the render itself.

Optimized image transfer from ImageRender to buffer.
    Previously, images that were transferred to the host were always going through
    buffers in VideoTexture. It is now possible to transfer ImageRender
    images to external buffer without intermediate copy (i.e. directly from OGL to buffer)
    if the attributes of the ImageRender objects are set as follow:
       flip=False, alpha=True, scale=False, depth=False, zbuff=False.
       (if you need to flip the image, use camera negative scale)

3 files changed, 181 insertions, 21 deletions

diff --git a/doc/python_api/rst/bge.logic.rst b/doc/python_api/rst/bge.logic.rst
index 3f35901234a..5cdb8ebfee9 100644
--- a/doc/python_api/rst/bge.logic.rst
+++ b/doc/python_api/rst/bge.logic.rst
@@ -378,6 +378,28 @@ General functions
 
    Render next frame (if Python has control)
 
+.. function:: setRender(render)
+
+   Sets the global flag that controls the render of the scene. 
+   If True, the render is done after the logic frame.
+   If False, the render is skipped and another logic frame starts immediately.
+
+   .. note::
+
+      GPU VSync no longer limits the number of frame per second when render is off, 
+      but the *Use Frame Rate* option still regulates the fps. To run as many frames
+      as possible, untick this option (Render Properties, System panel).
+
+   :arg render: the render flag
+   :type render: bool
+
+.. function:: getRender()
+
+   Get the current value of the global render flag
+
+   :return: The flag value
+   :rtype: bool
+
 **********************
 Time related functions
 **********************
diff --git a/doc/python_api/rst/bge.render.rst b/doc/python_api/rst/bge.render.rst
index 3b565e294dd..02c3beef672 100644
--- a/doc/python_api/rst/bge.render.rst
+++ b/doc/python_api/rst/bge.render.rst
@@ -90,6 +90,48 @@ Constants
 
    Right eye being used during stereoscopic rendering.
 
+.. data:: RAS_OFS_RENDER_BUFFER
+
+   The pixel buffer for offscreen render is a RenderBuffer. Argument to :func:`offScreenCreate`
+
+.. data:: RAS_OFS_RENDER_TEXTURE
+
+   The pixel buffer for offscreen render is a Texture. Argument to :func:`offScreenCreate`
+
+
+*****
+Types
+*****
+
+.. class:: RASOffScreen
+
+   An off-screen render buffer object. 
+
+   Use :func:`offScreenCreate` to create it.
+   Currently it can only be used in the :class:`bge.texture.ImageRender`
+   constructor to render on a FBO rather than the default viewport.
+
+  .. attribute:: width
+
+     The width in pixel of the FBO
+
+     :type: integer
+
+  .. attribute:: height
+
+     The height in pixel of the FBO
+
+     :type: integer
+
+  .. attribute:: color
+
+     The underlying OpenGL bind code of the texture object that holds
+     the rendered image, 0 if the FBO is using RenderBuffer.
+     The choice between RenderBuffer and Texture is determined
+     by the target argument of :func:`offScreenCreate`.
+
+     :type: integer
+
 
 *********
 Functions
@@ -362,3 +404,22 @@ Functions
    Get the current vsync value
 
    :rtype: One of VSYNC_OFF, VSYNC_ON, VSYNC_ADAPTIVE
+
+.. function:: offScreenCreate(width,height[,samples=0][,target=bge.render.RAS_OFS_RENDER_BUFFER])
+
+   Create a Off-screen render buffer object.
+
+   :arg width: the width of the buffer in pixels
+   :type width: integer
+   :arg height: the height of the buffer in pixels
+   :type height: integer
+   :arg samples: the number of multisample for anti-aliasing (MSAA), 0 to disable MSAA
+   :type samples: integer
+   :arg target: the pixel storage: :data:`RAS_OFS_RENDER_BUFFER` to render on RenderBuffers (the default),
+      :data:`RAS_OFS_RENDER_TEXTURE` to render on texture. 
+      The later is interesting if you want to access the texture directly (see :attr:`RASOffScreen.color`).
+      Otherwise the default is preferable as it's more widely supported by GPUs and more efficient.
+      If the GPU does not support MSAA+Texture (e.g. Intel HD GPU), MSAA will be disabled.
+   :type target: integer
+   :rtype: :class:`RASOffScreen`
+
diff --git a/doc/python_api/rst/bge.texture.rst b/doc/python_api/rst/bge.texture.rst
index 4588a3e1800..e226d2f90c0 100644
--- a/doc/python_api/rst/bge.texture.rst
+++ b/doc/python_api/rst/bge.texture.rst
@@ -173,14 +173,23 @@ Video classes
       :return: Whether the video was playing.
       :rtype: bool
 
-   .. method:: refresh()
-
-      Refresh video - get its status.
-      
-      :value: see `FFmpeg Video and Image Status`_.
-
+   .. method:: refresh(buffer=None, format="RGBA", timestamp=-1.0)
+
+      Refresh video - get its status and optionally copy the frame to an external buffer.
+
+      :arg buffer: An optional object that implements the buffer protocol.
+         If specified, the image is copied to the buffer, which must be big enough or an exception is thrown.
+      :type buffer: any buffer type
+      :arg format: An optional image format specifier for the image that will be copied to the buffer.
+         Only valid values are "RGBA" or "BGRA"
+      :type format: str
+      :arg timestamp: An optional timestamp (in seconds from the start of the movie)
+         of the frame to be copied to the buffer.
+      :type timestamp: float
+      :return: see `FFmpeg Video and Image Status`_.
       :rtype: int
 
+
 *************
 Image classes
 *************
@@ -244,12 +253,17 @@ Image classes
          * :class:`FilterRGB24`
          * :class:`FilterRGBA32`
 
-   .. method:: refresh()
+   .. method:: refresh(buffer=None, format="RGBA")
 
-      Refresh image, i.e. load it.
+      Refresh image, get its status and optionally copy the frame to an external buffer.
       
-      :value: see `FFmpeg Video and Image Status`_.
-
+      :arg buffer: An optional object that implements the buffer protocol.
+         If specified, the image is copied to the buffer, which must be big enough or an exception is thrown.
+      :type buffer: any buffer type
+      :arg format: An optional image format specifier for the image that will be copied to the buffer.
+         Only valid values are "RGBA" or "BGRA"
+      :type format: str
+      :return: see `FFmpeg Video and Image Status`_.
       :rtype: int
 
    .. method:: reload(newname=None)
@@ -411,9 +425,18 @@ Image classes
       
       :type: :class:`~bgl.Buffer` or None
 
-   .. method:: refresh()
+   .. method:: refresh(buffer=None, format="RGBA")
 
-      Refresh image - invalidate its current content.
+      Refresh image - render and copy the image to an external buffer (optional)
+      then invalidate its current content.
+
+      :arg buffer: An optional object that implements the buffer protocol.
+         If specified, the image is rendered and copied to the buffer,
+         which must be big enough or an exception is thrown.
+      :type buffer: any buffer type
+      :arg format: An optional image format specifier for the image that will be copied to the buffer.
+         Only valid values are "RGBA" or "BGRA"
+      :type format: str
 
    .. attribute:: scale
 
@@ -498,9 +521,17 @@ Image classes
       
       :type: :class:`~bgl.Buffer` or None
 
-   .. method:: refresh()
+   .. method:: refresh(buffer=None, format="RGBA")
+
+      Refresh image - calculate and copy the image to an external buffer (optional) then invalidate its current content.
 
-      Refresh image - invalidate its current content.
+      :arg buffer: An optional object that implements the buffer protocol.
+         If specified, the image is calculated and copied to the buffer,
+         which must be big enough or an exception is thrown.
+      :type buffer: any buffer type
+      :arg format: An optional image format specifier for the image that will be copied to the buffer.
+         Only valid values are "RGBA" or "BGRA"
+      :type format: str
 
    .. attribute:: scale
 
@@ -545,14 +576,18 @@ Image classes
 
       :type: bool
 
-.. class:: ImageRender(scene, camera)
+.. class:: ImageRender(scene, camera, fbo=None)
 
    Image source from render.
+   The render is done on a custom framebuffer object if fbo is specified,
+   otherwise on the default framebuffer.
    
    :arg scene: Scene in which the image has to be taken.
    :type scene: :class:`~bge.types.KX_Scene`
    :arg camera: Camera from which the image has to be taken.
    :type camera: :class:`~bge.types.KX_Camera`
+   :arg fbo: Off-screen render buffer object (optional)
+   :type fbo: :class:`~bge.render.RASOffScreen`
 
    .. attribute:: alpha
 
@@ -599,10 +634,6 @@ Image classes
       
       :type: :class:`~bgl.Buffer` or None
 
-   .. method:: refresh()
-
-      Refresh image - invalidate its current content.
-
    .. attribute:: scale
 
       Fast scale of image (near neighbour).
@@ -640,6 +671,42 @@ Image classes
       
       :type: bool
 
+   .. method:: render()
+
+      Render the scene but do not extract the pixels yet.
+      The function returns as soon as the render commands have been send to the GPU.
+      The render will proceed asynchronously in the GPU while the host can perform other tasks.
+      To complete the render, you can either call :func:`refresh`
+      directly of refresh the texture of which this object is the source.
+      This method is useful to implement asynchronous render for optimal performance: call render()
+      on frame n and refresh() on frame n+1 to give as much as time as possible to the GPU
+      to render the frame while the game engine can perform other tasks.
+
+      :return: True if the render was initiated, False if the render cannot be performed (e.g. the camera is active)
+      :rtype: bool
+
+   .. method:: refresh()
+   .. method:: refresh(buffer, format="RGBA")
+
+      Refresh video - render and optionally copy the image to an external buffer then invalidate its current content.
+      The render may have been started earlier with the :func:`render` method,
+      in which case this function simply waits for the render operations to complete.
+      When called without argument, the pixels are not extracted but the render is guaranteed
+      to be completed when the function returns.
+      This only makes sense with offscreen render on texture target (see :func:`~bge.render.offScreenCreate`).
+
+      :arg buffer: An object that implements the buffer protocol.
+         If specified, the image is copied to the buffer, which must be big enough or an exception is thrown.
+         The transfer to the buffer is optimal if no processing of the image is needed.
+         This is the case if ``flip=False, alpha=True, scale=False, whole=True, depth=False, zbuff=False``
+         and no filter is set.
+      :type buffer: any buffer type of sufficient size
+      :arg format: An optional image format specifier for the image that will be copied to the buffer.
+         Only valid values are "RGBA" or "BGRA"
+      :type format: str
+      :return: True if the render is complete, False if the render cannot be performed (e.g. the camera is active)
+      :rtype: bool
+
 .. class:: ImageViewport
 
    Image source from viewport.
@@ -689,9 +756,19 @@ Image classes
       
       :type: sequence of two ints
 
-   .. method:: refresh()
+   .. method:: refresh(buffer=None, format="RGBA")
+
+      Refresh video - copy the viewport to an external buffer (optional) then invalidate its current content.
 
-      Refresh image - invalidate its current content.
+      :arg buffer: An optional object that implements the buffer protocol.
+         If specified, the image is copied to the buffer, which must be big enough or an exception is thrown.
+         The transfer to the buffer is optimal if no processing of the image is needed.
+         This is the case if ``flip=False, alpha=True, scale=False, whole=True, depth=False, zbuff=False``
+         and no filter is set.
+      :type buffer: any buffer type
+      :arg format: An optional image format specifier for the image that will be copied to the buffer.
+         Only valid values are "RGBA" or "BGRA"
+      :type format: str
 
    .. attribute:: scale