VideoTexture: new ImageRender class for Render To Texture

The new class VideoTexture.ImageRender() is available to perform
render to texture in the GE.

Constructor:

  VideoTexture.ImageRender(scene,cam)
    cam  : camera object that will be used for the render.
           It must be an inactive camera.
    scene: reference to the scene that will be rendered.
           The camera must be part of that scene.
  Returns an object that can be used as a source of a VideoTexture.Texture object

Methods: none

Attributes:

  background: 
     4-tuple representing the background color of the rendering
     as RGBA color components, each component being an integer 
     between 0 and 255. 
     Default value = [0,0,255,255] (=saturated blue)
     Note: athough the alpha component can be specified, it is not
           supported at the moment, the alpha channel of the rendered
           texture will always be 255. You can however introduce an
           alpha channel by appending a FilterBlueScreen() filter, it
           will set the alpha to 0 (transparent) on all pixels that were
           not rendered.

  capsize:
     2-tuple representing the size of the render area as [x,y] number of pixels.
     Default value = largest rectangle with power of 2 dimensions that fits in the canvas 
     You may want to reduce the render area to increase performance. For example,
     a render area of [256,128] is probably sufficient to implement a car inner mirror.
     For best performance, use power of 2 dimensions and don't set any filter: this
     allows direct transfer between the GPU frame buffer and texture memory
     without going through the host.

  alpha: 
     Boolean indicating if the render alpha channel should be copied to the texture.
     Default value: False
     Experimental, do not use.

  whole:
     Boolean indicating if the entire canvas should be used for the rendering. 
     Default value: False
     Note: There is no reason to set this attribute to True: the rendering will
           in any case be scaled down to the largest rectangle with power of 2
           dimensions before transfering to the texture.

Attributes inherited from the ImageBase class:

  image : image binary data, read-only
  size  : [x,y] size of the texture, read-only
  scale : set to True for fast scale down in case the render area dimensions are not power of 2
  flip  : set to True for vertical flip. 
  filter: set a post-processing filter on the render.

Notes:

* Aspect Ratio
For consistent results in Blender and Blenderplayer, the same aspect ratio used
by Blender to draw the camera viewport (Scene(F10)->Format tab->Size X/Size Y) 
is also used during the rendering. You can control the portion of the scene that
will be rendered by "looking through the camera": the zone inside the outer dotted 
rectangle will be rendered to the texture.
In order to reproduce the scene without X/Y distortion, you must apply the texture
on an object or portion of object that has the same aspect ratio.

* Order of rendering
The rendereing is performed when you call the refresh() method of the parent 
Texture object. This happens outside the normal frame rendering and will have no 
effect on it.
However, if you want to use ImageViewport and ImageRender at the same time, be 
sure to refresh the viewport texture before the render texture because the latter
will destroy the frame buffer that is used by the former to update the texture.

* Scene status
The meshes are not updated during the render to texture: the rendered texture
is one frame late to the rendered frame with regards to mesh deformation.

* Example:

  cont = GameLogic.getCurrentController()
  # object that receives the texture
  obj = contr.getOwner()
  scene = GameLogic.getCurrentScene()
  # camera used for the render
  tvcam = scene.getObjectList()['OBtvcam']
  # assume obj has some faces UV assigned to tv.png
  matID = VideoTexture.materialID(obj, 'IMtv.png')
  GameLogic.tv = VideoTexture.Texture(obj, matID)
  GameLogic.tv.source = VideoTexture.ImageRender(scene,tvcam)
  GameLogic.tv.source.capsize = [256,256]
  # to render the texture, just call GameLogic.tv.refresh(True) on each frame.

You can download a demo game (with a video file) here:

  http://home.scarlet.be/~tsi46445/blender/VideoTextureDemo.zip

For those who have already downloaded the demo, you can just update the blend file:

  http://home.scarlet.be/~tsi46445/blender/VideoTextureDemo.blend

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