[Bf-committers] Anymated textures in the 3Dview

[Benoit Bolsee]

Hi,

Recently, based on my status of the VideoTexture module mantainer, I've
been asked whether video textures could be displayed dynamically in the
3D view (based on frame number). Unfortunately, the BGE and Blender use
a different realtime render engine, so the VideoTexture module is no use
in Blender.

Nevertheless, I've studied the question and isolated the places in the
code that must be changed to allow dynamic textures in the 3D view. I
thought I would release this information as some Blender dev might want
to implement the changes.

/benoit

>>>>> Here is the study:

I finally had the time to look into that. It is not a simple problem. I
have identified the 2 missing links to get animated texture in the 3D
view but I'm not confident to implement them. The affected code is part
of the Blender UI render engine that I'm not familiar with.

I can give pointers to the code. Note that the following explanations
are applicable to Blender 2.5.

The function that is not doing the right thing is GPU_verify_image() in
source/blender/gpu/gpu_draw.c This function is called whenever a
textured face must be rendered in the 3D view. It calls the
BKE_image_get_ibuf() function (line 447) to get the image buffer. Note
that it uses a Image object, which is the central place in Blender where
images are stored, including images from movies. It passes NULL as
second argument, which means that the last loaded image from the movie
will be returned.

This is not a problem if the image corresponding to the current frame
was loaded before this function is called. Unfortunately, there is no
proper mechanism in Blender to ensure that. I found that displaying the
Texture in the Button panel partially works: the frame number is updated
whenever you modify something on that panel. This could be fixed by
proper notifier/event but has the inconvenient that you have to keep the
texture panel opened. A better way would be scan all Images (there is a
global link of such objects) and update those pointing to movies
whenever the frame number is changed. I don't think that is particularly
difficult to do.

The second problem is at line 446: if the image was already bound to a
GPU texture, it simply rebinds and the image is not reloaded.  The
proper load code is below at line 553. The idea would be to keep at
Image level the number of the frame that was last loaded on the GPU and
if it differs from the frame returned by BKE_image_get_ibuf, reload the
image. Again I don't think this is complicated to do.

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