Collapse passes more aggressively in the face of size changes.

[movit] / effect.h

diff --git a/effect.h b/effect.h
index 9d95705f6a66ce344a54bd18eb83154018d85c35..fbe39d7274a421fd9f906ae809fdace3df7a8bc2 100644 (file)
--- a/effect.h
+++ b/effect.h
@@ -161,12 +161,38 @@ public:
        // needs mipmaps, you will also get them).
        virtual bool needs_mipmaps() const { return false; }
 
+       // Whether there is a direct correspondence between input and output
+       // texels. Specifically, the effect must not:
+       //
+       //   1. Try to sample in the border (ie., outside the 0.0 to 1.0 area).
+       //   2. Try to sample between texels.
+       //   3. Sample with an x- or y-derivative different from -1 or 1.
+       //      (This also means needs_mipmaps() and one_to_one_sampling()
+       //      together would make no sense.)
+       //
+       // The most common case for this would be an effect that has an exact
+       // 1:1-correspondence between input and output texels, e.g. SaturationEffect.
+       // However, more creative things, like mirroring/flipping or padding,
+       // would also be allowed.
+       //
+       // The primary gain from setting this is that you can sample directly
+       // from an effect that changes output size (see changes_output_size() below),
+       // without going through a bounce texture. It won't work for effects that
+       // set sets_virtual_output_size(), though.
+       //
+       // Does not make a lot of sense together with needs_texture_bounce().
+       virtual bool one_to_one_sampling() const { return false; }
+
        // Whether this effect wants to output to a different size than
-       // its input(s) (see inform_input_size(), below). If you set this to
-       // true, the output will be bounced to a texture (similarly to if the
-       // next effect set needs_texture_bounce()).
+       // its input(s) (see inform_input_size(), below). See also
+       // sets_virtual_output_size() below.
        virtual bool changes_output_size() const { return false; }
 
+       // Whether your get_output_size() function (see below) intends to ever set
+       // virtual_width different from width, or similar for height.
+       // It does not make sense to set this to true if changes_output_size() is false.
+       virtual bool sets_virtual_output_size() const { return changes_output_size(); }
+
        // Whether this effect is effectively sampling from a a single texture.
        // If so, it will override needs_texture_bounce(); however, there are also
        // two demands it needs to fulfill: